US1501293A - Method of coating metals, flux therefor, etc. - Google Patents

Description

Patented July 15, 1924.1

STATES RICHARD STAACK, or NORTH BERGEN,

LEAD COATING WORKS, A

NEW JERSEY, ASSIGNOB TO RICHQRD STAAGK CORPORATION OF NEW JERSEY.

METHOD OF COATING METALS. FLUX. THEREFOR, ETC.

No Drawing.

T 0 all whom it may concern.

Be it. known that I, RICHARD SIAACK, a citizen of the United States, residing at North Bergen, in the county of Hudson and State of New Jersey, have invented certain new and useful Improvements in Methods of Coating Metals, Flux Therefor, Etc, of which the following is a specification. V

This invention relates to the covering of metals with a protective coat or envelope to prevent corrosion, as for instance to the covering of iron or steel with a coating of lead, in such manner as to form on the iron or other metal, a closely adherent and con tinuous envelope or coat, substantially free from pin holes or breaks, and one which will effectually prevent and will preserve the metal from the eifects of the atmosphere and other deteriorating influences.

The need of such a protective coat for metal has long been recognized, and many attempts have been made to produce the same, but as far as I am aware without success. The prior attempts to this end have been characterized by the cleaning of the metal by subjecting it to different kinds of cleaning operations. most frequently by means of acid pickling solutions, the appli cation to the cleansed metal of a flux, and finally the immersion of the metal in amolten bath of the coating metal. These characteristic operations have been carried on under different conditions and with the use of different, kinds of pickling solutions, fluxes, and metal baths. but to my knowledge no commercially satisfactory coating has ever been produced which has successfully resisted corrosion and has protected the metal from the effects of the deteriorating influences to which in practice it is exposed.

As a result of many experiments and operations carried out under practical conditions, I have discovered that by the treatment of the metal in a certain way and under certain conditions. and with the use' of an improved flux. and of a metal bath of certain ingredients. I am enabled to apply to the metal a non-corrosive envelope or coat which is closely adherent to the metal, is continuous in structure, practically free from pin holes or breaks, and which a ords corrosion "or oxidation Application filed February 8, 1923. Serial No. 617,842.

an effective preventive against corrosion or oxidation for an indefinite time.

y invention therefore consists of an improved method of treating metals to give them a protective non-corrosive coating; and also of the improved flux employed in carrying out. the method; and the method of treating coating baths to incorporate phosphorus therein.

In the specification to follow I shall point .out and describe the details of my improved method, the materials used in carrying out the same, and the results thereof; and in the appended claims I shall set forth the novel characteristics and features of the invention.

In the use of my invention, in applying a protective coating of lead to iron or steel for instance, the preferred method of procedure is as follows:

The metal to be coated-is first thoroughly cleansed of scale, oil, grease and other foreign substances. This cleansing may be effected in variousiways now known to those skilled in the art, but I have found that the most satisfactory results are obtained if the article is first heated to redness, -prefer-' ably a dull red, or say to a temperature of from 1100 to 1200 F. depending upon the thickness and size of the article,-and then quenched in a suitable pickling solution. This heating of the article is preferably and conveniently effected by means of a heating flame playing upon it, the purpose of the heating being two fold,--first, to consume or drive oftthe oil and grease, etc., and second, to open the pores of the metal in order that the ensuing action of the pickling solution may be moreetlieacious. p

A pickling solution or bath which I have found to be satisfactory for the purpose, consists of a 5% to 7% solution of hydrochloric acid maintained from about 110 to 140 F. The article is kept in this solution for about three minutes more or less according to the nature of the article. After removal. of the article from the pickling solution, it is Washed in Water'so as to free it of the acid. Under certain conat a temperature of ditions it may be desirable to use lower tembe increased. I have fo'uid that the articles to be coated are sometimes in such condition as to require treatment preliminary to the above heating and pickling, such as a pickle in dilute hydrofluoric acid, e. g. 15% strength.

The cleansed article has next applied to it a flux, which is conveniently effected by plunging the article in a bath of flux solution and allowing it to remain there for a sulticient time to become thoroughly covered with the solution and for the latter to penetrate the pores of the metal. The treatment of the article by the particular flux solution I employ, constitutes a very important step in the process, and in connection with the subsequent application ofthe molten coating material, itfacilitates and aids in the close union of the coating material with, and its adherence to, the metal of the article. The fluxing material which I employ for this purpose is a chloride solution, preferably chloride of zinc, containing phosphorus, such as is made by dissolving metallic zinc in hydrochloric acid of about 20%. commercial strength until the acid is nearly spent. This solution is diluted by the addition of water in suflicient quantity to leave in the solution a slight excess of acid, and to it is added a suitable quantity of phosphorus, say 2 ounces of phosphorus to 20 gallons eat the solution. The addition of the phosphorus to the solution may be conveniently effected by the use of so-called match sul hur technically known as phosphorus-sesqui-sulfide or tetra-phosphorus-tri-sulfide, which usually contains about 43 to 44% of sulphur and 56 to 57% of phosphorus. This match sulphur is in lump form and the quantity added contains a greater amount of phosphorus than the solution will dissolve, my intent being to introduce and maintain a maximum of phosphorus in the flux. On the addition of the match sulphur. the phosphorus is liberated from the sulphur and absorbed in, the flux solution.

I have found that the immersion of the article for 30 seconds in the flux bath under the described conditions is sullicient for my purposes.

IVhile I prefer to add the phosphorus to the chloride solution by the use of so-called match sulphur as above described. it will be understood that itmay be introduced in other ways.

.On removal of the article from the fluxing bath, and preferably while still wet with the flux solution, it is immersed in a metal coating bath. This coating bath is composed mainly of lead in molten "condition, with which is mixed a comparatively small quantity of phosphorus, and should be at a temperature of from 740 to 750 F. In one formof my invention, the bath is made by .tin.

melting ninety-seven pounds of pure lead and adding to it three ounds of phosphor- The immersion oi the article in this bath should be effected slowly so asto revent sputtering, and it should remain there.- in long enough to attain the temperature of the bath, one half minute or more, depending upon the size and thickness of the article.

On the removal of the article from the metal coating bath, if it be alarge article. it may be simply laid aside and the coating allowed to chill and set; but where smaller articles are coated, they are preferably agitated after removal from the coating bath to prevent them from adhering to each other, and then may be dropped into kerosene or other quenching medium to cool them.

In order to give the article a thicker coating than would be applied by a single immersion as described, it may be immersed in a second bath of coating metal,-in other words, subjected to the so-called double dip. This may be effected by immersing the article, after the primary coat has set, in a secondbath having preferably a lower temperature than the first bath, say from 600 to 650 F. according to the melting point of the second bath. This second bath may be similar in its ingredients to .the first bath, or it'may be free from tin and phosphorus and may contain a relatively small amount of antimony or other metal, say from 5% to 15%, which will have the effect of lowering the melting point of the bath. This will give a harder and thicker second coat to the article. It may be desirable to quench the article between the two immersions, with a pickling solution, or with a flux solution, to render the surface thoroughly receptive to the coating metal.

lVhile I may introduce the phosphorus into the metal coating bath by the use of phosphor-tin as described, it will be understood that it may be added in other Ways, as for instance in the form of any phosphide or compound containing phosphorus.

By employing a chloride flux solution containing phosphorus. followed by a metal coating bath also containingphosphorus. in the treatment of the article to 'be coated as above described. not only is the metal oft-he article made highly receptive to the close adhesion thereto of the metal of the coating bath. but also the latter is in the most favorable condition to bring about a close and efi'ective adherence of the coating metal to the article. The presence of the phosphorus both in the fluXing solution and in the coating bath, acts chemically I believe to form on the surface of the article. toa greater or less extent, a phosphide or phosphides of iron. which constitute an intimate bond of adhesion between the lead of the bath and the iron of the article, and thereby results in a very effective coating of the lead, continuous and pin-hole-free in character. The coating therefore considered as an entirety is of a stratified character, consisting first of an underlying stratum of iron phosphide or phosphides immediately on the surface of the article, and a stratum of lead and phosphorus superimposed on the first stratum; and if the article is subjected to a subsequent dip or dips, as described, additional strata will be imposed on those first laid, such additional strata containing antimony or other metals, according to the particular ingredients of the-additional baths.

The phosphorus in the coating bath has also a de-gasifying and de-oxidizing effect on the metal bath and surface of the iron article, and results in a more continuous coating than would be the case if oxids and gases were present, as these would cause a less perfect bond between the coating metal and the metal of the article.

The action of the lead in adhering to the article is facilitated by a certain amount of hydrostatic pressure exerted by the bath on the immersed article, which pressure may have the effect of forcing the lead into the the phosphorus content Apparently pores and interstices of the metal. The osmotic pressure between the bath and the article coated also acts to the same end.

In the practice of my process under practical conditions, I have found it desirable to add phosphorus to the molten coating bath from time to time, in order to prevent from being reduced to an undue degree or from being entirely exhausted by thecontinued use of the bath. but a very small percentage of thephosphorus content in a given amount of phosphor-tin, is absorbed by. the'lead of the bath, the remainder and greater portion of the phosphorus released by the tin when the latter melts, escaping or passing into the dross. A portion of this small phosphorus content forms, with the lead of the bath, phosphide of lead, and the remaining portion combines with the iron of the immersed article and forms phos hide of iron, so that unless the supply of p osphorus is kept up, there will be a constant loss, in the continued use of the bath on successive articles. By adding phosphorus from time to time as above described, the proper content is maintained in the continued use of the bath, and there will always be cle in forming the phosphide of iron stratum thereon.

While I have in the foregoing description set forth my invention as applicable by way of example to the coating of iron or steel with lead the invention may be applied to the coatin of brass, bronze, cop er and like metals wit lead, in which case have found present a sufficient amount to combine with the iron of the arti-I it advisable to employ as the pickling solution, a mixture of nitric and sulphuric acids, in which the article should be. immersed for a moment only. This solution is in the proportions of 30% of nitric acid to of sulphuric acid.

In using the method in the field, where pickling solutions and bath tanks areimpracticable, and when erected structures such as steel bridges, steel building frameworks, and the like, are to be coated, the metal is cleaned by sand blasting, then the protective metal containing phosphorus and previously ground to a fine powder is mixed with the chloride flux solution to the consistency of metallic paint, and is applied to the metal structure to drench the same, and the wet composition is subjected'to the action of direct heat which may be applied by means of a blow torch or otherwise, in order to reduce the protective metal to a molten state.

Having thus described my invention, what I claim is:

1. The method of covering metal with a protective metal coating, which consists in cleansing the metal to be coated, drenching the cleansed metal with a flux containing phosphorus, and uniting with the drenched metal a protective metal in molten condition containing phos horus. 2. The metho of covering metal with a protective metal coating, which consists in cleansing themetal to be coated, applying thereto a flux containing phosphorus, an immersing the flux covered metal in a bath of molten protective metal containing phoshorus.

3. The met which consists in cleansing the metal, applying thereto a fiux containing phosphorus, and finally immersing the metal in a bath of molten lead containing phosphorus.

4. The method of coating metal with lead, which consists in cleansing the metal, applying thereto a flux containing phosphorus in solution, and while the metal is still wet with the flux solution, immersing the samein a bath of molten lead containing phosphorus.

5-. The method of coating metal with a protective metal covering, which consists in cleansing the metal to be coated, applying thereto a chloride flux containing phosphorus, and immersing the flux covered metal in a bath of molten protective metal.

6. The method of coating metal with a protectiv lead covering, which consists in cleansing the metal, applying thereto a chloride flux containing phosphorus, and immersing the metal in? a bath of molten lead containing phosphorus.

7. The method of coatin metal with a protective lead covering, w ich consists 1n cleansing the metal, applying thereto a chloride flux containing phosphorus, and mod of coating metal withlead,

mersin the metal in a bath of molten lead. 8. T e method of covering metal with a protective lead coating, which consists in cleansing. the metal, applying thereto a chloride of zinc flux containing phosphorus, and immersing the metal in a bath of molten lead containing phosphorus.

9. The method of covering metal with a protective lea-d coating, which consists in cleansing the metal, applying thereto a suitable flux, immersing the metal in a bath of molten lead to give it a primary coating, allowing said coating to set, and immersing the coated metal in a molten lead bath of lower temperature. than the first bath to give the metal a second coating.

10. The method of covering metal with a protective metal coating, which consists in cleansing the metal to be coated, applying thereto a suitable flux, immersing the metal in a bath of molten lead to. give it a primary coating, allowing said coating to set, subjecting said coated metal to a treatment to make it receptive to a second lead covering, and immersing the metal in a bath of molten lead to give it a second coating.

11. The method of covering metal with a protective lead coating, which consists in cleansing the metal, applying thereto a flux consisting of a solution of chloride of zinc containing phosphorus in the proportion of two ounces of phosphorus to-twenty gallons of the solution, and immersing the metal in a bath of molten lead containing phosphorus.

12. The method of covering metal with a protective lead coating, which consists in cleansing the metal, applying thereto a chloride. flux containing phosphorus-sesqui-sulfide, and immersing the metal in a molten lead bath.

13. The method of covering metal with a protective lead coating, which consists in cleansing the metal, applying thereto a chloride flux containing phosphorus-sesquisulfide, and immersing the metal in amolten lead bath containing phosphorus.

14. The method of covering metal with a protective lead coatin which consists in heating the metal to re ness, applying thereto while the metal is in heated condition, an

acid pickling solution, freeing themetal 'of the pickling solution, applying to the metal a chloriik. flux solution containing phosphorus, and immersing the metal while still wet with the flux solution, in a molten lead bath umtaining phosphorus.

15. A flux fpr use in covering metal with a protective metal coating, consisting of a chloride flux solution containing phos-. phorus.

16. A flux for use in covering metal With a protective metal coating, consisting of a solution of chloride of zinc containing phosphorus.

17 A flux for use in covering metal'with a protective metal coating, consisting of a dilute solution of chloride of zinc contain- 21 The method of covering metal with I a protective 'coating, which consists in cleansing the metal, applying thereto a su1t able flux, immersing the flux covered metal in a bath of molten protective metal containing phosphorus, and adding phosphorus to the coating bath from time to time to maintain its proper phosphorus content.

' 22. The method of covering ferrous metal with a protective lead coating, which consists in cleansing the metal, applying thereto a suitable flux, immersing the flux covered metal in a molten lead bath containing phosphorus, and adding phosphorus to the bath from time to time to maintain its proper phosphorus content. 1

23. The method of treating a molten metal coating bath, to incorporate phosphorus therein, which consists in fusing phosphor tin in the bath.

24:. The'method of treating a molten lead therein, which consists infusing phosphortin in the bath.

25. The method of treating a molten lead coating bath to incorporate phosphorus therein, which consists in fusingphosphortin in the bath in the proportions of substantially 3 pounds-of phosphor-tin and 97 pounds of lead.

In testimony whereof, I have afiixed my signature hereto.

RICHARD STAACK.

coating bath to incorporate phosphorus