US2991205A - Method of improving corrosion resistance of stainless steel - Google Patents
Method of improving corrosion resistance of stainless steel Download PDFInfo
- Publication number
- US2991205A US2991205A US702534A US70253457A US2991205A US 2991205 A US2991205 A US 2991205A US 702534 A US702534 A US 702534A US 70253457 A US70253457 A US 70253457A US 2991205 A US2991205 A US 2991205A
- Authority
- US
- United States
- Prior art keywords
- stainless steel
- corrosion resistance
- coating
- chromate
- film
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Lifetime
Links
- 238000005260 corrosion Methods 0.000 title claims description 38
- 230000007797 corrosion Effects 0.000 title claims description 38
- 238000000034 method Methods 0.000 title claims description 28
- 229910001220 stainless steel Inorganic materials 0.000 title description 59
- 239000010935 stainless steel Substances 0.000 title description 54
- 238000000576 coating method Methods 0.000 claims description 39
- 239000011248 coating agent Substances 0.000 claims description 32
- 229910045601 alloy Inorganic materials 0.000 claims description 12
- 239000000956 alloy Substances 0.000 claims description 12
- VYZAMTAEIAYCRO-UHFFFAOYSA-N Chromium Chemical compound [Cr] VYZAMTAEIAYCRO-UHFFFAOYSA-N 0.000 claims description 8
- 229910052804 chromium Inorganic materials 0.000 claims description 8
- 239000011651 chromium Substances 0.000 claims description 8
- 229910001256 stainless steel alloy Inorganic materials 0.000 claims description 8
- ZCDOYSPFYFSLEW-UHFFFAOYSA-N chromate(2-) Chemical compound [O-][Cr]([O-])(=O)=O ZCDOYSPFYFSLEW-UHFFFAOYSA-N 0.000 description 29
- 238000005498 polishing Methods 0.000 description 23
- 239000000243 solution Substances 0.000 description 15
- 239000003638 chemical reducing agent Substances 0.000 description 14
- KRVSOGSZCMJSLX-UHFFFAOYSA-L chromic acid Substances O[Cr](O)(=O)=O KRVSOGSZCMJSLX-UHFFFAOYSA-L 0.000 description 14
- AWJWCTOOIBYHON-UHFFFAOYSA-N furo[3,4-b]pyrazine-5,7-dione Chemical compound C1=CN=C2C(=O)OC(=O)C2=N1 AWJWCTOOIBYHON-UHFFFAOYSA-N 0.000 description 14
- UOUJSJZBMCDAEU-UHFFFAOYSA-N chromium(3+);oxygen(2-) Chemical class [O-2].[O-2].[O-2].[Cr+3].[Cr+3] UOUJSJZBMCDAEU-UHFFFAOYSA-N 0.000 description 10
- 238000011065 in-situ storage Methods 0.000 description 10
- JEIPFZHSYJVQDO-UHFFFAOYSA-N iron(III) oxide Inorganic materials O=[Fe]O[Fe]=O JEIPFZHSYJVQDO-UHFFFAOYSA-N 0.000 description 10
- 229910000831 Steel Inorganic materials 0.000 description 8
- 239000000463 material Substances 0.000 description 8
- 239000010959 steel Substances 0.000 description 8
- 238000011049 filling Methods 0.000 description 6
- NLKNQRATVPKPDG-UHFFFAOYSA-M potassium iodide Chemical compound [K+].[I-] NLKNQRATVPKPDG-UHFFFAOYSA-M 0.000 description 6
- 229910000975 Carbon steel Inorganic materials 0.000 description 5
- 239000007864 aqueous solution Substances 0.000 description 5
- 230000000694 effects Effects 0.000 description 5
- FAPWRFPIFSIZLT-UHFFFAOYSA-M Sodium chloride Chemical compound [Na+].[Cl-] FAPWRFPIFSIZLT-UHFFFAOYSA-M 0.000 description 4
- HCHKCACWOHOZIP-UHFFFAOYSA-N Zinc Chemical compound [Zn] HCHKCACWOHOZIP-UHFFFAOYSA-N 0.000 description 4
- PNEYBMLMFCGWSK-UHFFFAOYSA-N aluminium oxide Inorganic materials [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 description 4
- 229910052793 cadmium Inorganic materials 0.000 description 4
- BDOSMKKIYDKNTQ-UHFFFAOYSA-N cadmium atom Chemical compound [Cd] BDOSMKKIYDKNTQ-UHFFFAOYSA-N 0.000 description 4
- 239000010962 carbon steel Substances 0.000 description 4
- 150000003839 salts Chemical class 0.000 description 4
- 229910052725 zinc Inorganic materials 0.000 description 4
- 239000011701 zinc Substances 0.000 description 4
- WSFSSNUMVMOOMR-UHFFFAOYSA-N Formaldehyde Chemical compound O=C WSFSSNUMVMOOMR-UHFFFAOYSA-N 0.000 description 3
- 239000002253 acid Substances 0.000 description 3
- 238000001035 drying Methods 0.000 description 3
- 239000002932 luster Substances 0.000 description 3
- 238000005554 pickling Methods 0.000 description 3
- 239000000843 powder Substances 0.000 description 3
- 238000012360 testing method Methods 0.000 description 3
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 3
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 2
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 description 2
- LYCAIKOWRPUZTN-UHFFFAOYSA-N Ethylene glycol Chemical compound OCCO LYCAIKOWRPUZTN-UHFFFAOYSA-N 0.000 description 2
- PEDCQBHIVMGVHV-UHFFFAOYSA-N Glycerine Chemical compound OCC(O)CO PEDCQBHIVMGVHV-UHFFFAOYSA-N 0.000 description 2
- VEXZGXHMUGYJMC-UHFFFAOYSA-N Hydrochloric acid Chemical compound Cl VEXZGXHMUGYJMC-UHFFFAOYSA-N 0.000 description 2
- QIGBRXMKCJKVMJ-UHFFFAOYSA-N Hydroquinone Chemical compound OC1=CC=C(O)C=C1 QIGBRXMKCJKVMJ-UHFFFAOYSA-N 0.000 description 2
- PXHVJJICTQNCMI-UHFFFAOYSA-N Nickel Chemical compound [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 description 2
- GRYLNZFGIOXLOG-UHFFFAOYSA-N Nitric acid Chemical compound O[N+]([O-])=O GRYLNZFGIOXLOG-UHFFFAOYSA-N 0.000 description 2
- ISWSIDIOOBJBQZ-UHFFFAOYSA-N Phenol Chemical compound OC1=CC=CC=C1 ISWSIDIOOBJBQZ-UHFFFAOYSA-N 0.000 description 2
- OAICVXFJPJFONN-UHFFFAOYSA-N Phosphorus Chemical compound [P] OAICVXFJPJFONN-UHFFFAOYSA-N 0.000 description 2
- NINIDFKCEFEMDL-UHFFFAOYSA-N Sulfur Chemical compound [S] NINIDFKCEFEMDL-UHFFFAOYSA-N 0.000 description 2
- QAOWNCQODCNURD-UHFFFAOYSA-N Sulfuric acid Chemical compound OS(O)(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-N 0.000 description 2
- 238000005275 alloying Methods 0.000 description 2
- 238000005097 cold rolling Methods 0.000 description 2
- 238000005530 etching Methods 0.000 description 2
- 238000010438 heat treatment Methods 0.000 description 2
- 239000012535 impurity Substances 0.000 description 2
- 238000004519 manufacturing process Methods 0.000 description 2
- 229910052751 metal Inorganic materials 0.000 description 2
- 239000002184 metal Substances 0.000 description 2
- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical compound C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 description 2
- BDAGIHXWWSANSR-UHFFFAOYSA-N methanoic acid Natural products OC=O BDAGIHXWWSANSR-UHFFFAOYSA-N 0.000 description 2
- 229910017604 nitric acid Inorganic materials 0.000 description 2
- 229910052698 phosphorus Inorganic materials 0.000 description 2
- 239000011574 phosphorus Substances 0.000 description 2
- 229910052710 silicon Inorganic materials 0.000 description 2
- 239000010703 silicon Substances 0.000 description 2
- 239000011780 sodium chloride Substances 0.000 description 2
- 239000007921 spray Substances 0.000 description 2
- 235000000346 sugar Nutrition 0.000 description 2
- 150000005846 sugar alcohols Polymers 0.000 description 2
- 229910052717 sulfur Inorganic materials 0.000 description 2
- 239000011593 sulfur Substances 0.000 description 2
- OSWFIVFLDKOXQC-UHFFFAOYSA-N 4-(3-methoxyphenyl)aniline Chemical compound COC1=CC=CC(C=2C=CC(N)=CC=2)=C1 OSWFIVFLDKOXQC-UHFFFAOYSA-N 0.000 description 1
- ZNBNBTIDJSKEAM-UHFFFAOYSA-N 4-[7-hydroxy-2-[5-[5-[6-hydroxy-6-(hydroxymethyl)-3,5-dimethyloxan-2-yl]-3-methyloxolan-2-yl]-5-methyloxolan-2-yl]-2,8-dimethyl-1,10-dioxaspiro[4.5]decan-9-yl]-2-methyl-3-propanoyloxypentanoic acid Chemical compound C1C(O)C(C)C(C(C)C(OC(=O)CC)C(C)C(O)=O)OC11OC(C)(C2OC(C)(CC2)C2C(CC(O2)C2C(CC(C)C(O)(CO)O2)C)C)CC1 ZNBNBTIDJSKEAM-UHFFFAOYSA-N 0.000 description 1
- 239000010965 430 stainless steel Substances 0.000 description 1
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 1
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 description 1
- FBPFZTCFMRRESA-FSIIMWSLSA-N D-Glucitol Natural products OC[C@H](O)[C@H](O)[C@@H](O)[C@H](O)CO FBPFZTCFMRRESA-FSIIMWSLSA-N 0.000 description 1
- FBPFZTCFMRRESA-KVTDHHQDSA-N D-Mannitol Chemical compound OC[C@@H](O)[C@@H](O)[C@H](O)[C@H](O)CO FBPFZTCFMRRESA-KVTDHHQDSA-N 0.000 description 1
- FBPFZTCFMRRESA-JGWLITMVSA-N D-glucitol Chemical compound OC[C@H](O)[C@@H](O)[C@H](O)[C@H](O)CO FBPFZTCFMRRESA-JGWLITMVSA-N 0.000 description 1
- CWYNVVGOOAEACU-UHFFFAOYSA-N Fe2+ Chemical compound [Fe+2] CWYNVVGOOAEACU-UHFFFAOYSA-N 0.000 description 1
- 229930195725 Mannitol Natural products 0.000 description 1
- ZOKXTWBITQBERF-UHFFFAOYSA-N Molybdenum Chemical compound [Mo] ZOKXTWBITQBERF-UHFFFAOYSA-N 0.000 description 1
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 description 1
- 229930006000 Sucrose Natural products 0.000 description 1
- CZMRCDWAGMRECN-UGDNZRGBSA-N Sucrose Chemical compound O[C@H]1[C@H](O)[C@@H](CO)O[C@@]1(CO)O[C@@H]1[C@H](O)[C@@H](O)[C@H](O)[C@@H](CO)O1 CZMRCDWAGMRECN-UGDNZRGBSA-N 0.000 description 1
- ATJFFYVFTNAWJD-UHFFFAOYSA-N Tin Chemical compound [Sn] ATJFFYVFTNAWJD-UHFFFAOYSA-N 0.000 description 1
- RTAQQCXQSZGOHL-UHFFFAOYSA-N Titanium Chemical compound [Ti] RTAQQCXQSZGOHL-UHFFFAOYSA-N 0.000 description 1
- GSEJCLTVZPLZKY-UHFFFAOYSA-N Triethanolamine Chemical compound OCCN(CCO)CCO GSEJCLTVZPLZKY-UHFFFAOYSA-N 0.000 description 1
- 150000007513 acids Chemical class 0.000 description 1
- 238000007792 addition Methods 0.000 description 1
- 238000000137 annealing Methods 0.000 description 1
- 239000010953 base metal Substances 0.000 description 1
- 230000003796 beauty Effects 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 229910052799 carbon Inorganic materials 0.000 description 1
- 230000015556 catabolic process Effects 0.000 description 1
- 239000003795 chemical substances by application Substances 0.000 description 1
- 238000004140 cleaning Methods 0.000 description 1
- 239000010941 cobalt Substances 0.000 description 1
- 229910017052 cobalt Inorganic materials 0.000 description 1
- GUTLYIVDDKVIGB-UHFFFAOYSA-N cobalt atom Chemical compound [Co] GUTLYIVDDKVIGB-UHFFFAOYSA-N 0.000 description 1
- 239000003086 colorant Substances 0.000 description 1
- 229910052802 copper Inorganic materials 0.000 description 1
- 239000010949 copper Substances 0.000 description 1
- 235000019441 ethanol Nutrition 0.000 description 1
- 239000004744 fabric Substances 0.000 description 1
- 238000005755 formation reaction Methods 0.000 description 1
- 235000019253 formic acid Nutrition 0.000 description 1
- 235000011187 glycerol Nutrition 0.000 description 1
- 229910052739 hydrogen Inorganic materials 0.000 description 1
- 239000001257 hydrogen Substances 0.000 description 1
- 125000004435 hydrogen atom Chemical class [H]* 0.000 description 1
- WGCNASOHLSPBMP-UHFFFAOYSA-N hydroxyacetaldehyde Natural products OCC=O WGCNASOHLSPBMP-UHFFFAOYSA-N 0.000 description 1
- 229910000378 hydroxylammonium sulfate Inorganic materials 0.000 description 1
- 239000004615 ingredient Substances 0.000 description 1
- 229910052500 inorganic mineral Inorganic materials 0.000 description 1
- 239000004922 lacquer Substances 0.000 description 1
- WPBNNNQJVZRUHP-UHFFFAOYSA-L manganese(2+);methyl n-[[2-(methoxycarbonylcarbamothioylamino)phenyl]carbamothioyl]carbamate;n-[2-(sulfidocarbothioylamino)ethyl]carbamodithioate Chemical compound [Mn+2].[S-]C(=S)NCCNC([S-])=S.COC(=O)NC(=S)NC1=CC=CC=C1NC(=S)NC(=O)OC WPBNNNQJVZRUHP-UHFFFAOYSA-L 0.000 description 1
- 239000000594 mannitol Substances 0.000 description 1
- 235000010355 mannitol Nutrition 0.000 description 1
- 239000011707 mineral Substances 0.000 description 1
- 229910052750 molybdenum Inorganic materials 0.000 description 1
- 239000011733 molybdenum Substances 0.000 description 1
- 229910052759 nickel Inorganic materials 0.000 description 1
- 239000010955 niobium Substances 0.000 description 1
- GUCVJGMIXFAOAE-UHFFFAOYSA-N niobium atom Chemical compound [Nb] GUCVJGMIXFAOAE-UHFFFAOYSA-N 0.000 description 1
- 229910052757 nitrogen Inorganic materials 0.000 description 1
- 150000007524 organic acids Chemical class 0.000 description 1
- 230000003647 oxidation Effects 0.000 description 1
- 238000007254 oxidation reaction Methods 0.000 description 1
- 230000001590 oxidative effect Effects 0.000 description 1
- 239000004033 plastic Substances 0.000 description 1
- 229920003023 plastic Polymers 0.000 description 1
- 238000002360 preparation method Methods 0.000 description 1
- 238000013102 re-test Methods 0.000 description 1
- 230000000717 retained effect Effects 0.000 description 1
- 239000002904 solvent Substances 0.000 description 1
- 239000000600 sorbitol Substances 0.000 description 1
- 235000010356 sorbitol Nutrition 0.000 description 1
- 229960004793 sucrose Drugs 0.000 description 1
- 150000008163 sugars Chemical class 0.000 description 1
- 229910052718 tin Inorganic materials 0.000 description 1
- 239000011135 tin Substances 0.000 description 1
- 239000010936 titanium Substances 0.000 description 1
- 229910052719 titanium Inorganic materials 0.000 description 1
- WFKWXMTUELFFGS-UHFFFAOYSA-N tungsten Chemical compound [W] WFKWXMTUELFFGS-UHFFFAOYSA-N 0.000 description 1
- 229910052721 tungsten Inorganic materials 0.000 description 1
- 239000010937 tungsten Substances 0.000 description 1
- 229910052720 vanadium Inorganic materials 0.000 description 1
- LEONUFNNVUYDNQ-UHFFFAOYSA-N vanadium atom Chemical compound [V] LEONUFNNVUYDNQ-UHFFFAOYSA-N 0.000 description 1
- 239000001993 wax Substances 0.000 description 1
Classifications
-
- C—CHEMISTRY; METALLURGY
- C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
- C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
- C23C22/00—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals
- C23C22/05—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using aqueous solutions
- C23C22/06—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using aqueous solutions using aqueous acidic solutions with pH less than 6
- C23C22/24—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using aqueous solutions using aqueous acidic solutions with pH less than 6 containing hexavalent chromium compounds
- C23C22/30—Chemical surface treatment of metallic material by reaction of the surface with a reactive liquid, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using aqueous solutions using aqueous acidic solutions with pH less than 6 containing hexavalent chromium compounds containing also trivalent chromium
Definitions
- This invention relates to improving the corrosion resistance of stainless steel surfaces and particularly to a method of improving the corrosion resistance of polished stainless steel articles.
- stainless steel is given a chromate film or finish such as is conventionally applied to zinc and cadmium coated steel articles.
- the coated stainless steel is then polished with a fine grit polishing powder or by bufling to bring back the bright and lustrous metallic finish. Polishing is com "ice trolled so that the stainless steel surface is not reduced more than about 2 mils and for optimum results, not more than 0.6 mil.
- Such a stainless steel treated in the manner described exhibits corrosion resistance far superior to untreated stainless steel surfaces.
- Chromate formations such as are applied in the method of the present invention are well known for coating zinc and cadmium coated steel.
- Processes for obtaining a chromate film involve contacting the cleaned surfaceof the article being treated with an aqueous solution that contains chromic acid plus a reducing agent.
- the reducing agent may be one of the mineral acids such as hydrochloric and sulfuric acid but also may be an organic acid such as formic acid.
- the article While the article is being withdrawn from the aqueous solution, it acquires a thin gelatinous-like coating which is subsequently permitted to dry or is cured by heating at a low temperature of about 200 F. or 300 F.
- Such a film offers. protection to the zinc or cadmium coating from corrosive breakdown.
- chromate coatings are commonly referred to as chromate coatings and are believed to be composed of a material of the formula
- the chromate films may be applied to carbon steel surfaces that are not coated with such materials as zinc and cadmium. Processes for accomplishing this are taught in U.S. Patents Nos. 2,768,103 and 2,768,104, issued to Schuster et a1. These processes involve contacting a treated steel, such as Blackplate, with an aqueous chromic acid bath plus a reducing agent.
- the steel surface is first cleaned by a pretreatment, such as solvent and alkaline cleaning, pickling, nitric acid etching, phosphatizing, oxide coating, etc., and is thereafter chromate coated by contacting the surface with aqueous chromic acid plus reducing agent, such coating being then dried or cured.
- a pretreatment such as solvent and alkaline cleaning, pickling, nitric acid etching, phosphatizing, oxide coating, etc.
- a clean surface of carbon steel is contacted for at least one second with an aqueous solution consisting essentially of about /2 to about 30% chromic acid and about to 25% of a reducing agent.
- Preferred reducing agents are those that do not form stable oxidation products or water soluble salts with the chromic acid. Both the chromic acid and the reducing agent may be applied simultaneously from the same solution or the reducing agent may be applied separately after coating.
- Representative reducing agents are the straight chain polyalcohols such as glycol, glycerine, mannitol, sorbitol and sugars generally, as well as conventional reducing agents such as potassium iodide, phenol, hydroquinone, phosphorus acid, hydroxylamine sulfate, triethanolamine, and the like. Hydrogen, methane, formaldehyde vapors, ethyl alcohol vapors, and similar gaseous reducing agents may be utilized in lieu of or supplementary to the agents mentioned previously.
- the concentration of reducing agent in the solution should be less than the concentration of chromic acid and the solution bath temperature should be preferably between about 50 F. and 200 F.
- the length of time the carbon steel article is held in the solution is not critical but should be for a time of at least one second.
- a gelatinous film is carried on the surface of the metal, which film is subsequently dried. Drying is preferably accomplished within the temperaturerangeoffrom 200 F. to.300 'F. 1
- stainless steel is chromate coated. It has been found that surface preparation, such as is required in the processes of coating carbon steels taught by the Schuster et al. patents, is not necessary when chromate coating stainless steels. While it is desirable for the stainless steel to have a clean surface, no special etching or oxidizing steps are required.
- the preferred CrO bath and coating conditions are substantially the same as those employed in Patent No. 2,768,104.
- the chromate coated stainless steel is polished sufi'iciently to remove any outward appearance of the film, leaving a metallic bright appearance. However, care must be taken that not all of the film is completely removed. This film is actually only a few millionths of an inch thick.
- Polishing should not remove more than about 2 mils from the surface of the stainless steel. Optimum results are obtained when the surface is reduced 0.6 mil or less. Bxcellent results have been obtained when only about 0.1 mil of the stainless steel surface has been removed by polishing. Polishing is preferably accomplished with very fine grain materials, such as 320 grit or finer, in that coarse polishing materials will scratch the surface of the stainless steel. However, even a scratched surface will exhibit some improved corrosion resistance if chromate coated before polishing. Bufiing may follow grit polishing or the entire polishing may be accomplished by buflfing with a cloth wheel of conventional manufacture.
- a distinct advantage of an embodiment of the present invention is the fact that the chromate coating is applied to the stainless steel in its sheet or strip form and before conventional forming operations.
- stainless steel sheet or strip is chromate coated before a drawing operation is applied to the coated sheet and the drawn or otherwise formed article is buflEed in the conventional manner without performing any additional operations not ordinarily performed after drawing.
- the polishing effects a redistribution of the chromate coating to effectively fill the pits and voids normally present in the surface of stainless steel sheet as well as fine cracks or voids in the chromate coating that may have been formed by reason of the mechanical deformation applied during the fabrication of the article.
- Stainless steel that may be treated in accordance with the present invention includes all of the ferrous base metals commonly referred to as stainless steel such as the A181 types of the 200, 300 and 400 series. Such steels contain, among other alloying ingredients, mainly chromium within the range between 10% and 35%.
- the stainless steels to which the method of the present invention is applicable many contain the usual impurities such as silicon, phosphorus, sulfur, copper, tin, etc. These elements are usually present in quantities of less than 1%; however, larger quantities of these elements may be added for special effects. For example, up to 3 silicon or up to 1% sulfur may be purposely employed.
- Other alloying additions include up to 35% nickel, up to 20% manganese, and up to about 5% of molybdenum, tungsten, titanium,
- columbium, vanadium and cobalt carbon is usually below about .25%. There also may be traces of rare earths. Nitrogen is usually present as an impurity but up to 0.60% may be purposely added.
- Polished and bufied stainless steel as normally produced contains numerous microscopic pits and voids which are believed to be the cause of corrosion. These pits or voids act to nucleate or initiate corrosion when the steel is exposed to corrosive conditions.
- the present invention improves the corrosion resistance of stainless steel in that the voids normally present are filled with a material which will not permit their nucleating corrosion. Although polishing restores the bright and lustrous metallic finish, it does not remove the entire coating, as suflicient chromate film is retained and flowed into the pits and voids to give a smooth surface and to improve corrosion resistance.
- the method of the present invention is particularly applicable to stainless steels with bright and lustrous finishes in that dull finishes do not lend themselves to light polishing and buffing after chromate coating and will not provide significantly improved corrosion resistance unless polished and buffed to a point where the chromate coat is entirely removed. It is desirable to apply the method of the present invention to stainless steels that exhibit a polish at least equivalent to or brighter than a No. 4 finish.
- a No. 4 finish on stainless steel is well known in the steel industry as a ground finish obtained by employing about to grit materials.
- the present method is particularly applicable to finer finishes such as auto mobile grade stainless steel strip. The finish of this material is obtained by a final cold rolling through extra smooth rolls after the usual cold rolling, annealing and pickling operations.
- Such a finish is generally of higher luster and smoothness than a No. 4 finish. Excellent results may be obtained on No. 7 and No. 8 stainless steel finishes which are ground and buffed surfaces.
- the method is also equally applicable to lustrous finishes ob tained initially by means other than mechanical such as electropolishing and bright pickling.
- Specimens of type 430 stainless steel strip that exhibited a bright and lustrous finish were cleaned in an electrolytic alkaline bath. Some of the specimens were chromate coated by immersing them in an aqueous solution that contained about 2.0% chromic acid (CrO and about 0.66% cane sugar at room temperature (about 70 F.). The chromate coatings were then cured by heating the specimens in an oven until they reached a temperature of 400 F. A coating weight of about 40 milligrams per square foot was obtained. Coated and uncoated specimens were formed into Erichsen cups with a deformation of 7 millimeters and some specimens of each were given a light butt. All the samples were exposed to 20% salt spray (20%, by weight, NaCl in water). Results were as follows:
- article with improved corrosion resistance which comprises, contacting a bright clean surface of stainless steel Table I Metal Re- Test No. Polishing Operation 1 moved By Results-48 Hrs. Results-113 Hrs.
- Coated and lightly bufled 0 .do Do No coating, lightly bufled.. 0 -do 1 fflalediun, small and 50 e spo s. N 0 coating, no bufl. 0
- alumina and bufled Coated and polished with 180+240+320 grit 1.0 2fine rust spots small, 30 fine spots.
- alumina powder and buffed Coated and polished with 120+180+240+320 1. 5 N o rusting or pitting 5 small, 5 fine, 460 very fine grit alumina owder and buffed. spots. Coated and po bed with 60+120+180+240+ 2.0 1 small rust spot 1 medium, 10 small, fine 320 grit A110 powder and buffed.
- Polishing was conducted with commercial grade polishing belt of successive grit sizes as indicated.
- Test No. 2 showed equivalent corrosion resistance to test No. 1 although buifing had substantially restored the natural metallic luster of the stainless steel surface. Also it can be seen that all the examples that had been coated and polished or buffed showed superior corrosion resistance to test No. 4 which was an untreated specimen as tested. Also, all the specimens showed some superior corrosion resistance to Example 3 which was a bufied but otherwise untreated sample. All samples except sample No. 1 showed a bright and lustrous automobile grade strip finish. Sample No. 1 had such a finish but exhibited a chromate coat.
- the method of providing improved corrosion resistance to a bright stainless steel article normally having microscopic pits and voids therein which comprises, providing said article with a chromate film comprising an in situ formed film of hydrated mixed chromium oxides mechanically polishing said article so as to reduce the surface thereof not more than 0.6 mil so as to remove the appearance of said chromate film while flowing the chromate to insure the filling of the microscopic pits and voids therewith.
- the method of producing a formed stainless steel article with improved corrosion resistance comprises, applying to the surface of a stainless steel alloy normally having microscopic pits and voids therein an in situ formed film of hydrated mixed chromium oxides, mechanically forming said alloy into the desired shape and mechanically polishing the surface of said formed stainless steel so as to remove the appearance of said film while flowing the said film to insure the filling of the microscopic pits and voids therewith.
- the method of producing a formed stainless steel article with improved corrosion resistance which comprises, applying to the surface of a stainless steel alloy normally having microscopic pits and voids therein an in situ formed film of hydrated mixed chromium oxides, mechanically forming said alloy into the desired shape and mechanically polishing the surface of said formed stainless steel so as to reduce the surface thereof not more than 0.6 mil so as to remove the appearance of said film while flowing the said film to insure the filling of the microscopic pits and voids therewith.
- the method of producing a formed stainless steel article with improved corrosion resistance comprises, contacting a bright clean surface of stainless steel normally having microscopic pits and voids therein with a chrornic acid solution containing from about /z% to about 30% CrO at a temperature of about 50 F.
- a method for improving the corrosion resistance of chromium type stainless steel alloys which comprises applying to the surface of said alloys an in situ formed coating of hydrated mixed chromium oxides and then bufling down the coating until its presence is not apparent to the eye.
- a method for improving the corrosion resistance of chromium type stainless steel alloys which comprises contacting said alloys with an aqueous chromic acid solution containing from about /2 to about 30% CrO and from about 4% to about 25% of a reducing agent which will reduce CrO to form substantially water insoluble salts therewith so as to form an in situ coating of hydrated mixed chromium oxides on said alloys and then bufiing down the coating until its presence is not apparent to the eye.
- a method for improving the corrosion resistance of chromium type stainless steel alloys which comprises, con- 7 tacting said alloys with an aqueous chromic acid solution containing from about /1 to about 30% CrO and from about A to about 25% of sugar so as to form an in situ coating of hydrated mixed chromium oxides on said alloys and then bufiing down the coating until its presence is not apparent to the eye.
- a method for improving the corrosion resistance of chromium type stainless steel alloys which comprises, contacting said alloys with an aqueous chromic acid solu tion containing from about /2% to about 30% C10 and from about A% to about 25% of polyalcohol so as to form an in situ coating of hydrated mixed chromium oxides on said alloys and then buifing down the coating until its presence is not apparent to the eye.
- a method for improving the corrosion resistance of chromium type stainless steel alloys which comprises,
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Description
United States Patent sylvania No Drawing. Filed Dec. 13, 1957, Ser. No. 702,534
Claims. (Cl. 148-63.)
This invention relates to improving the corrosion resistance of stainless steel surfaces and particularly to a method of improving the corrosion resistance of polished stainless steel articles.
In the process of producing stainless steel for commercial applications, it is usually desirable to obtain the maximum possible corrosion resistance properties. This is particularly the case where the stainless steel is to be exposed to corrosive environments such as outdoor applicat-ion's, particularly building and automobile trim. Bufiing and polishing stainless steels efiect an attractive and desirable bright metallic finish which is ideal for such applications, and also improves the corrosion resistance of the stainless steel surface. However, exposure to ordinary corrosive atmospheric conditions, such as industrial atmospheres, or in the case of automobile trim exposure to the corrosive effects of salts employed for highway use, invariably causes corrosion of the stainless steel utilized for such purpose and shortens the life and attractiveness of stainless steel articles. Methods of improving the corrosion resistance of such articles are constantly being sought and any improvement obtained in securing improved corrosion resistance is of importance in this field.
Many coatings have been developed which increase the corrosion resistance of stainless steel surfaces; however, a majority of them detract from the desired bright metallic finish and are relatively unattractive and therefore are undesirable. Transparent finishes such as lacquers, plastics and waxes oifer only temporary protection and soon erode or peel away, exposing the stainless steel to the corrosive environment.
It has now been found that by means of the present invention improved corrosion resistance of stainless steel articles may be obtained while retaining the natural bright metallic luster.
It is an object of the present invention to provide a stainless steel article that exhibits improved corrosion resistance.
It is also an object of the present invention to provide a means of improving the corrosion resistance of bright and lustrous stainless steel without destroying the beauty of the natural metallic finish. It is a further object of the present invention to provide a method of filling the microscopic pits and voids normally found on the surface of conventionally polished stainless steel with a material that will prevent nucleating corrosion in the vicinity of such pits and voids.
Other objects and advantageous features of the present invention will be obvious from the following description.
In the practice of the present invention stainless steel is given a chromate film or finish such as is conventionally applied to zinc and cadmium coated steel articles. The coated stainless steel is then polished with a fine grit polishing powder or by bufling to bring back the bright and lustrous metallic finish. Polishing is com "ice trolled so that the stainless steel surface is not reduced more than about 2 mils and for optimum results, not more than 0.6 mil. Such a stainless steel treated in the manner described exhibits corrosion resistance far superior to untreated stainless steel surfaces.
1 Chromate formations such as are applied in the method of the present invention are well known for coating zinc and cadmium coated steel. Processes for obtaining a chromate film involve contacting the cleaned surfaceof the article being treated with an aqueous solution that contains chromic acid plus a reducing agent. The reducing agent may be one of the mineral acids such as hydrochloric and sulfuric acid but also may be an organic acid such as formic acid. While the article is being withdrawn from the aqueous solution, it acquires a thin gelatinous-like coating which is subsequently permitted to dry or is cured by heating at a low temperature of about 200 F. or 300 F. Such a film offers. protection to the zinc or cadmium coating from corrosive breakdown. These coatings are commonly referred to as chromate coatings and are believed to be composed of a material of the formula The chromate films may be applied to carbon steel surfaces that are not coated with such materials as zinc and cadmium. Processes for accomplishing this are taught in U.S. Patents Nos. 2,768,103 and 2,768,104, issued to Schuster et a1. These processes involve contacting a treated steel, such as Blackplate, with an aqueous chromic acid bath plus a reducing agent. The steel surface is first cleaned by a pretreatment, such as solvent and alkaline cleaning, pickling, nitric acid etching, phosphatizing, oxide coating, etc., and is thereafter chromate coated by contacting the surface with aqueous chromic acid plus reducing agent, such coating being then dried or cured.
Particularly desirable results are obtained when a clean surface of carbon steel is contacted for at least one second with an aqueous solution consisting essentially of about /2 to about 30% chromic acid and about to 25% of a reducing agent. Preferred reducing agents are those that do not form stable oxidation products or water soluble salts with the chromic acid. Both the chromic acid and the reducing agent may be applied simultaneously from the same solution or the reducing agent may be applied separately after coating. Representative reducing agents are the straight chain polyalcohols such as glycol, glycerine, mannitol, sorbitol and sugars generally, as well as conventional reducing agents such as potassium iodide, phenol, hydroquinone, phosphorus acid, hydroxylamine sulfate, triethanolamine, and the like. Hydrogen, methane, formaldehyde vapors, ethyl alcohol vapors, and similar gaseous reducing agents may be utilized in lieu of or supplementary to the agents mentioned previously. The concentration of reducing agent in the solution should be less than the concentration of chromic acid and the solution bath temperature should be preferably between about 50 F. and 200 F. .The length of time the carbon steel article is held in the solution is not critical but should be for a time of at least one second. As the metal is withdrawn from the solution it is found that a gelatinous film is carried on the surface of the metal, which film is subsequently dried. Drying is preferably accomplished within the temperaturerangeoffrom 200 F. to.300 'F. 1
In accordance with Patent No. 2,768,103 particularly desirable results are obtained when the carbon steel is etched with a nitric acid bath prior to chromate coating. Such a practice has been found to be nonbeneficial when coating stainless steel. Chromate coated stainless steel exhibits a variety of colors depending on the thickness of the coat. Heavy coatings create interference patterns which are objectionable. Lighter coatings are bluish gray and very light coatings (10 to 20 mg. per square foot) exhibit a yellowish cast.
In the present invention stainless steel is chromate coated. It has been found that surface preparation, such as is required in the processes of coating carbon steels taught by the Schuster et al. patents, is not necessary when chromate coating stainless steels. While it is desirable for the stainless steel to have a clean surface, no special etching or oxidizing steps are required. The preferred CrO bath and coating conditions are substantially the same as those employed in Patent No. 2,768,104. The chromate coated stainless steel is polished sufi'iciently to remove any outward appearance of the film, leaving a metallic bright appearance. However, care must be taken that not all of the film is completely removed. This film is actually only a few millionths of an inch thick. Polishing should not remove more than about 2 mils from the surface of the stainless steel. Optimum results are obtained when the surface is reduced 0.6 mil or less. Bxcellent results have been obtained when only about 0.1 mil of the stainless steel surface has been removed by polishing. Polishing is preferably accomplished with very fine grain materials, such as 320 grit or finer, in that coarse polishing materials will scratch the surface of the stainless steel. However, even a scratched surface will exhibit some improved corrosion resistance if chromate coated before polishing. Bufiing may follow grit polishing or the entire polishing may be accomplished by buflfing with a cloth wheel of conventional manufacture.
A distinct advantage of an embodiment of the present invention is the fact that the chromate coating is applied to the stainless steel in its sheet or strip form and before conventional forming operations. Thus, stainless steel sheet or strip is chromate coated before a drawing operation is applied to the coated sheet and the drawn or otherwise formed article is buflEed in the conventional manner without performing any additional operations not ordinarily performed after drawing. Stainless steel articles fabricated from the chromate coated stainless steel sheet or strip as by drawing or otherwise mechanically deforming the sheet into the shape and size of the articles and which are thereafter polished as taught herein, exhibit superior corrosion resistance to identical articles formed in an identical manner from the same stainless steel but which have not been chromate coated and polished, or if chromate coated, have not been polished. The polishing, as by buffing as described, effects a redistribution of the chromate coating to effectively fill the pits and voids normally present in the surface of stainless steel sheet as well as fine cracks or voids in the chromate coating that may have been formed by reason of the mechanical deformation applied during the fabrication of the article.
Stainless steel that may be treated in accordance with the present invention includes all of the ferrous base metals commonly referred to as stainless steel such as the A181 types of the 200, 300 and 400 series. Such steels contain, among other alloying ingredients, mainly chromium within the range between 10% and 35%. The stainless steels to which the method of the present invention is applicable many contain the usual impurities such as silicon, phosphorus, sulfur, copper, tin, etc. These elements are usually present in quantities of less than 1%; however, larger quantities of these elements may be added for special effects. For example, up to 3 silicon or up to 1% sulfur may be purposely employed. Other alloying additions include up to 35% nickel, up to 20% manganese, and up to about 5% of molybdenum, tungsten, titanium,
columbium, vanadium and cobalt. Carbon is usually below about .25%. There also may be traces of rare earths. Nitrogen is usually present as an impurity but up to 0.60% may be purposely added.
Polished and bufied stainless steel as normally produced contains numerous microscopic pits and voids which are believed to be the cause of corrosion. These pits or voids act to nucleate or initiate corrosion when the steel is exposed to corrosive conditions. The present invention improves the corrosion resistance of stainless steel in that the voids normally present are filled with a material which will not permit their nucleating corrosion. Although polishing restores the bright and lustrous metallic finish, it does not remove the entire coating, as suflicient chromate film is retained and flowed into the pits and voids to give a smooth surface and to improve corrosion resistance.
The method of the present invention is particularly applicable to stainless steels with bright and lustrous finishes in that dull finishes do not lend themselves to light polishing and buffing after chromate coating and will not provide significantly improved corrosion resistance unless polished and buffed to a point where the chromate coat is entirely removed. It is desirable to apply the method of the present invention to stainless steels that exhibit a polish at least equivalent to or brighter than a No. 4 finish. A No. 4 finish on stainless steel is well known in the steel industry as a ground finish obtained by employing about to grit materials. The present method is particularly applicable to finer finishes such as auto mobile grade stainless steel strip. The finish of this material is obtained by a final cold rolling through extra smooth rolls after the usual cold rolling, annealing and pickling operations. Such a finish is generally of higher luster and smoothness than a No. 4 finish. Excellent results may be obtained on No. 7 and No. 8 stainless steel finishes which are ground and buffed surfaces. The method is also equally applicable to lustrous finishes ob tained initially by means other than mechanical such as electropolishing and bright pickling.
The following specific examples are given to illustrate the process of the present invention and in no way limit the invention to the exact methods set forth.
Specimens of type 430 stainless steel strip that exhibited a bright and lustrous finish were cleaned in an electrolytic alkaline bath. Some of the specimens were chromate coated by immersing them in an aqueous solution that contained about 2.0% chromic acid (CrO and about 0.66% cane sugar at room temperature (about 70 F.). The chromate coatings were then cured by heating the specimens in an oven until they reached a temperature of 400 F. A coating weight of about 40 milligrams per square foot was obtained. Coated and uncoated specimens were formed into Erichsen cups with a deformation of 7 millimeters and some specimens of each were given a light butt. All the samples were exposed to 20% salt spray (20%, by weight, NaCl in water). Results were as follows:
Sample Result 1. Uncoated, unbufied 2. Uncoated, buffed 3. Coated, unbuffed 4. Coated, bufied A number of small rust spots appear in 48 hours.
No rust spots at 48 hours; some spots appear alter 72 hours.
Rust spots appear on deformed area after hours.
No rust spots after 600 hours.
spray (an aqueous solution of 20% of NaCl) at room temperature. Results were as follows:
article with improved corrosion resistance which comprises, contacting a bright clean surface of stainless steel Table I Metal Re- Test No. Polishing Operation 1 moved By Results-48 Hrs. Results-113 Hrs.
- Polishing,
Mlls
Coated but not bufied No rusting or pitting No rusting or pitting. Coated and lightly bufled 0 .do Do No coating, lightly bufled.. 0 -do 1 fflalediun, small and 50 e spo s. N 0 coating, no bufl. 0 A number of small rust Numerous rust spots and spots after 16 hrs. general corrosion. Coated and heavily buffed 0 No rusting or pitting 3 fine rust spots. Cggaltdind polished with 320 grit alumina and 0. 1 do 4 fine rust spots.
e Coated and polished with 240 grit and 320 grit 0. 6 do 1 small, 40 fine spots.
alumina and bufled. Coated and polished with 180+240+320 grit 1.0 2fine rust spots small, 30 fine spots.
alumina powder and buffed. Coated and polished with 120+180+240+320 1. 5 N o rusting or pitting 5 small, 5 fine, 460 very fine grit alumina owder and buffed. spots. Coated and po bed with 60+120+180+240+ 2.0 1 small rust spot 1 medium, 10 small, fine 320 grit A110 powder and buffed.
and numerous very fine spots.
1 Polishing was conducted with commercial grade polishing belt of successive grit sizes as indicated.
It may be seen from the examples of Table I that although the advantages of polishing and buffing chromate coated stainless steel are not so pronounced as where drawing or forming operations after coating have taken place, it is obvious that beneficial corrosion resistance is obtained. Test No. 2. showed equivalent corrosion resistance to test No. 1 although buifing had substantially restored the natural metallic luster of the stainless steel surface. Also it can be seen that all the examples that had been coated and polished or buffed showed superior corrosion resistance to test No. 4 which was an untreated specimen as tested. Also, all the specimens showed some superior corrosion resistance to Example 3 which was a bufied but otherwise untreated sample. All samples except sample No. 1 showed a bright and lustrous automobile grade strip finish. Sample No. 1 had such a finish but exhibited a chromate coat.
We claim:
1. The method of providing improved corrosion resistance to a bright stainless steel article normally having microscopic pits and voids therein which comprises, providing said article with a chromate film comprising an in situ formed film of hydrated mixed chromium oxides mechanically polishing said article so as to reduce the surface thereof not more than 0.6 mil so as to remove the appearance of said chromate film while flowing the chromate to insure the filling of the microscopic pits and voids therewith.
2. The method of producing a formed stainless steel article with improved corrosion resistance which comprises, applying to the surface of a stainless steel alloy normally having microscopic pits and voids therein an in situ formed film of hydrated mixed chromium oxides, mechanically forming said alloy into the desired shape and mechanically polishing the surface of said formed stainless steel so as to remove the appearance of said film while flowing the said film to insure the filling of the microscopic pits and voids therewith.
3. The method of producing a formed stainless steel article with improved corrosion resistance which comprises, applying to the surface of a stainless steel alloy normally having microscopic pits and voids therein an in situ formed film of hydrated mixed chromium oxides, mechanically forming said alloy into the desired shape and mechanically polishing the surface of said formed stainless steel so as to reduce the surface thereof not more than 0.6 mil so as to remove the appearance of said film while flowing the said film to insure the filling of the microscopic pits and voids therewith.
4. The method of producing a formed stainless steel sheet or strip normally having microscopic pits and voids on the surface thereof with an aqueous chromic acid solution containing from about /2% to about 30% CrO and from about A to 25 of a reducing agent that will partially reduce the OrO film that remains on said surface upon removal from the contacting solution so as to effect an in situ formed film of hydrated mixed chromium oxides on said surface, removing the contacted surface from the solution so that said film remains on the surface, drying said film, mechanically forming said steel into the desired shape and polishing the surface of said formed stainless steel so as to reduce the surface of said article not more than 0.6 mil so as to remove the appearance of said film while flowing the said film to insure the filling of the microscopic pits and voids therewith.
5. The method of producing a formed stainless steel article with improved corrosion resistance which comprises, contacting a bright clean surface of stainless steel normally having microscopic pits and voids therein with a chrornic acid solution containing from about /z% to about 30% CrO at a temperature of about 50 F. to about 200 F., removing the contacted surf-ace from the solution so that a film of the solution remains on the surface, drying said film on said surface while chemically reducing a portion of the chromic acid in the film so as to effect an in situ formed film of hydrated mix-ed chromium oxides, mechanically forming said stainless steel and polishing the surface of said formed stainless steel so as to reduce the surface of said article not more than about 0.6 mil so as to remove the appearance of said film while flowing said film to insure the filling of the microscopic pits and voids therewith.
6. A method for improving the corrosion resistance of chromium type stainless steel alloys which comprises applying to the surface of said alloys an in situ formed coating of hydrated mixed chromium oxides and then bufling down the coating until its presence is not apparent to the eye.
7. A method for improving the corrosion resistance of chromium type stainless steel alloys which comprises contacting said alloys with an aqueous chromic acid solution containing from about /2 to about 30% CrO and from about 4% to about 25% of a reducing agent which will reduce CrO to form substantially water insoluble salts therewith so as to form an in situ coating of hydrated mixed chromium oxides on said alloys and then bufiing down the coating until its presence is not apparent to the eye.
8. A method for improving the corrosion resistance of chromium type stainless steel alloys which comprises, con- 7 tacting said alloys with an aqueous chromic acid solution containing from about /1 to about 30% CrO and from about A to about 25% of sugar so as to form an in situ coating of hydrated mixed chromium oxides on said alloys and then bufiing down the coating until its presence is not apparent to the eye.
9. A method for improving the corrosion resistance of chromium type stainless steel alloys which comprises, contacting said alloys with an aqueous chromic acid solu tion containing from about /2% to about 30% C10 and from about A% to about 25% of polyalcohol so as to form an in situ coating of hydrated mixed chromium oxides on said alloys and then buifing down the coating until its presence is not apparent to the eye.
10. A method for improving the corrosion resistance of chromium type stainless steel alloys which comprises,
8 contacting said alloys with an aqueous chromic acid solution containing from about /2% to about 30% CrO and from about A% to about 25% of potassium iodide so as to form an in situ coating of hydrated mixed chromium oxides on said alloys and then bufiing down the coating until its presence is not apparent to the eye.
References Cited in the file of this patent UNITED STATES PATENTS 2,022,798 Bengston Dec. 3, 1935 2,104,667 Ostrofsky Jan. 4, 1938 2,106,227 Scharschu et al. Jan. 25, 1938 2,768,103 Schuster et al. Oct. 23, 1956 2,777,785 Schuster et a1 Jan. 15, 1957 2,788,292 Giesker et al. Apr. 9, 1957
Claims (1)
- 6. A METHOD FOR IMPROVING THE CORROSION RESISTANCE OF CHROMIUM TYPE STAINLESS STEEL ALLOYS WHICH COMPRISES APPLYING TO THE SURFACE OF SAID ALLOYS AN IN SITU FORMED COATING OF HYDRATED MIXED CHROMIUM OXIDES AND THEN BUFFING DOWN THE COATING UNTIL ITS PRESENCE IS NOT APPARENT TO THE EYE.
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| US702534A US2991205A (en) | 1957-12-13 | 1957-12-13 | Method of improving corrosion resistance of stainless steel |
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| US702534A US2991205A (en) | 1957-12-13 | 1957-12-13 | Method of improving corrosion resistance of stainless steel |
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Cited By (10)
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| US3201210A (en) * | 1963-01-03 | 1965-08-17 | Allegheny Ludlum Steel | Trim member assembly |
| US3201212A (en) * | 1962-06-22 | 1965-08-17 | Allegheny Ludlum Steel | Trim member |
| US3201211A (en) * | 1962-06-22 | 1965-08-17 | Allegheny Ludlum Steel | Stainless steel trim member |
| US3210220A (en) * | 1962-07-30 | 1965-10-05 | Norman E Clegg | Process for coating stainless steel |
| US3620777A (en) * | 1968-07-24 | 1971-11-16 | Hooker Chemical Corp | Chromate chemical coating solution for zinc alloy |
| US3942989A (en) * | 1970-10-22 | 1976-03-09 | Mayhew John T | White rust prevention for zinc coated surfaces |
| US5147597A (en) * | 1991-04-09 | 1992-09-15 | Electric Power Research Institute | Prestabilized chromium protective film to reduce radiation buildup |
| US20200115103A1 (en) * | 2018-10-15 | 2020-04-16 | Whit Gautreaux | Flask with attached tumblers |
| USD998400S1 (en) | 2021-08-18 | 2023-09-12 | High Camp Designs, Llc | Cocktail shaker |
| USD1015044S1 (en) | 2021-08-18 | 2024-02-20 | High Camp Designs, Llc | Cocktail shaker |
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| US2022798A (en) * | 1931-05-13 | 1935-12-03 | Aluminum Colors Inc | Manufacture of coated aluminum articles |
| US2104667A (en) * | 1933-04-15 | 1938-01-04 | Rustless Iron & Steel Corp | Treatment of rustless iron |
| US2106227A (en) * | 1935-04-29 | 1938-01-25 | Allegheny Steel Co | Surface treatment of metal to prevent localized corrosive attack |
| US2768103A (en) * | 1952-03-18 | 1956-10-23 | Heintz Mfg Co | Method for coating metals |
| US2777785A (en) * | 1953-07-30 | 1957-01-15 | Heintz Mfg Co | Composition for and method of treating metals as well as the treated product |
| US2788292A (en) * | 1951-10-15 | 1957-04-09 | Autoyre Co Inc | Method of treating chromium surfaces |
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| US2022798A (en) * | 1931-05-13 | 1935-12-03 | Aluminum Colors Inc | Manufacture of coated aluminum articles |
| US2104667A (en) * | 1933-04-15 | 1938-01-04 | Rustless Iron & Steel Corp | Treatment of rustless iron |
| US2106227A (en) * | 1935-04-29 | 1938-01-25 | Allegheny Steel Co | Surface treatment of metal to prevent localized corrosive attack |
| US2788292A (en) * | 1951-10-15 | 1957-04-09 | Autoyre Co Inc | Method of treating chromium surfaces |
| US2768103A (en) * | 1952-03-18 | 1956-10-23 | Heintz Mfg Co | Method for coating metals |
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Cited By (13)
| Publication number | Priority date | Publication date | Assignee | Title |
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| US3201212A (en) * | 1962-06-22 | 1965-08-17 | Allegheny Ludlum Steel | Trim member |
| US3201211A (en) * | 1962-06-22 | 1965-08-17 | Allegheny Ludlum Steel | Stainless steel trim member |
| US3210220A (en) * | 1962-07-30 | 1965-10-05 | Norman E Clegg | Process for coating stainless steel |
| US3201210A (en) * | 1963-01-03 | 1965-08-17 | Allegheny Ludlum Steel | Trim member assembly |
| US3620777A (en) * | 1968-07-24 | 1971-11-16 | Hooker Chemical Corp | Chromate chemical coating solution for zinc alloy |
| US3942989A (en) * | 1970-10-22 | 1976-03-09 | Mayhew John T | White rust prevention for zinc coated surfaces |
| US5147597A (en) * | 1991-04-09 | 1992-09-15 | Electric Power Research Institute | Prestabilized chromium protective film to reduce radiation buildup |
| US20200115103A1 (en) * | 2018-10-15 | 2020-04-16 | Whit Gautreaux | Flask with attached tumblers |
| US10723513B2 (en) * | 2018-10-15 | 2020-07-28 | High Camp | Flask with attached tumblers |
| USD970966S1 (en) | 2018-10-15 | 2022-11-29 | High Camp Designs, Llc | Flask with attached tumblers |
| US11542064B2 (en) | 2018-10-15 | 2023-01-03 | High Camp Designs, Llc | Flask with attached tumblers |
| USD998400S1 (en) | 2021-08-18 | 2023-09-12 | High Camp Designs, Llc | Cocktail shaker |
| USD1015044S1 (en) | 2021-08-18 | 2024-02-20 | High Camp Designs, Llc | Cocktail shaker |
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