US1808186A - Cleaning and preserving of metallic surfaces - Google Patents

Description

252. COMPOSITIONS,

Patented June 2, 1931 UNITED STATES PATENT OFFICE DEAL H. TOMPKINS, OF NITRO, WEST VIRGINIA, ASSIGNOR TO THE RUBBER SERVICE LABORATORIES COMPANY, OF AKRON, OHIO, A CORPORATION OF OHIO CLEANING AND PRIESERVING OF METALLIC SURFACES No Drawing.

The present invention relates to the cleaning and preservation of metallic surfaces, wherein the metal is in contact with a liquid of an acid nature. More particularly, the invention relates to the prevention of excessive pitting and embrittlement of a metal when subjected to an acid treating or pickling process.

Certain obj ects of the invention are to prevent the acid pickle liquor from attacking clean portions of the surface of a metal; to obviate over-pickling, embrittlement and pitting of the articles treated; to minimize the amount of metal lost in pickling; to increase the efficiency of the pickling operation and to prolong the effective life of the pickling bath and particularly to facilitate the pickling operation. Other and further objects of the invention will be apparent from the following description and accompanying examples.

In the art of pickling, the metal to be cleaned is treated with a dilute acid to remove oxides such as rust, scale, and other deposits, after which the metal is preferably washed with water and dipped into an alkaline bath to remove the last traces of free acid. The acid removes the rust and scale, but unfortunately, from the pickling standpoint, unless some agent to prevent such action is prescut, it attacks the cleaned metal itself, thereby causing loss of metal and producing an evolution of hydrogen gas, which escapes into the air, carrying with it a fine spray of the acid liquor from the bath and producing an atmosphere possessing corrosive prop: cities and one which is highly injurious to health.

By the present invention, these objectionable features of the pickling process are substantially overcome or reduced to a minimum. To accomplish the objects set forth in accordance with the present invention, there is added to the pickling bath a regulating agent or ingredient which acts to re- Application filed October 11, 1930. Serial No. 488,196.

strain the action of the acid from attacking clean metal but assists in removing the rust, scale and other deposits, or in other words causes the acid selectively to remove such materials without appreciably attacking the clean portions of the metal.

The pickle regulator or inhibitor, as disclosed in the present application, comprises a phosphoric acid derivative of reaction product of s'uifurdioxide" and an" aldehyde amine reaction product and "preferably a phosphoric "acid "derivative of a reaction product of sulfur dioxide and an aldehyde derivative of a Schiffs base; that is, a product formed by reacting an aldehyde with a Schifls base, adding sulfur dioxide thereto and treating the product so formed with phosphoric acid of any concentration necessary to produce chemical combination at the reaction temperature employed. The products hereinafter described and employable in the manner set forth are likewise useful in the cleaning of metals by immersion in or treatment with dilute solutions of non-oxidizing acids.

In the examples hereinafter set forth for carrying out the metal pickling process, conditions were imposed which duplicated, so far as possible, those commonly followed in commercial practice, so far as concerned acid concentrations and temperatures commonly employed.

Test pieces of steel approximately 4 x 3" in dimensions and known as 30 gauge low carbon hot rolled sheets, were immersed in approximately 640 cc. of a water solution of sulfuric acid containing approximately 6% by weight of 66 Be. acid to which had been added a small quantity of one of the preferred type of inhibitors. The loss in weight of the steel test pieces resulting from maintaining the strips in the pickle bath in the manner described for a definite period of time was then determined. The temperature of the pickling bath was maintained at from 176 to 185 F. (80 to 85 For the acid concentration set forth, commercial practice is to pickle at approximately 150 to 190 F. (66 to 88 C.). The results so obtained were compared with similar tests wherein the steel pieces were subjected, under the conditions set forth, to the action of an acid solution of the strength and for the time specified above, but containing no inhibitor.

One method whereby one of the preferred class of compounds, for example a phosphoric acid derivative of the reaction product of sulfur dioxide and an aldehyde derivative of a Schiifs base, was prepared follows:

Substantially one molecular proportion of the product formed from the reaction of substantially three molecular proportions of acetaldehyde and substantially two molecular proportions of aniline, according to the method set forth in U. S. Patent No. 1.659,152 granted to Clayton Olin North, was dissolved in an organic solvent, for example, a quantity of acetone equal to one-third of the weight of the aldehyde-amine product. Substantially one-half a molecular proportion of sulfur dioxide was passed thereinto at a rate slow enough for complete absorption and combination to take place while agitating and maintaining a temperature of approximately 30 to 60 C. To the product thus formed, substantially one molecular proportion of phosphoric acid, preferably having an acid strength of approximately 85%, was added at a temperature of substantially 50 to 7 0 C. After'the addition of the phosphoric acid was completed, the water present and the solvent employed, for example acetone, were removed preferably by evaporation. The product prepared in the manner described, aftercooling,was a brittle resin,which formed a fine powder when ground that was readily soluble in a pickle li uor, as for example dilute sulfuric acid. sample of the material prepared as described above was incorporated in a pickling bath in the manner hereinbefore described. Thus a steel test piece 3" x 4", 30 gauge low carbon hot rolled sheets, exposing 24 square inches of surface and weighing 18.770 grams, was found to lose but 0.298 grams after 40 minutes pickling in a 6% sulfuric acid solution containing 0.06 grams of the inhibiting product just described. A similar test piece weighing 17.928 grams and treated in the same manner. but without the use of any inhibitor, lost 7.165 grams. Thus, when the phosphoric acid derivative of the reaction product of sulfur dioxide and the product formed by reacting substantially three molecular proportions of aoetaldehyde and substantially two molecular proportions of aniline is employed as an inhibitor, the loss in weight per square inch of surface exposed corresponds to 0.0124 grams, whereas when no inhibitor is used the loss per square inch of surface exposed corresponds to 0.2985 grams. From these results it is apparent that the metal loss resulting by pickling in dilute sulfuric acid solution containing the inhibitor specified is only 4% as great as the loss resulting by ickling without the use of any inhibitor. K greater saving in metal losses results from the use of a larger amount of the inhibitor. Moreover, the steel plates pickled in the presence of the inhibitor set forth are clean and are not stained upon removal from the bath.

Other phosphoric acid derivatives of the reaction products of sulfur dioxide and aldehyde-amine products, and preferably phosphoric acid derivatives of the reaction products of sulfur dioxide and aldehyde derivatives of Schiifs bases have been prepared in a manner analogous to that hereinbefore set forth and tested as inhibitors in a pickling bath in the manner described.

Thus, the phosphoric acid derivatives of the sulfur dioxide reaction products of a Schiffs base and of aldehyde derivatives thereof as set forth hereinafter, were prepared in a manner analogous to that hereinbefore set forth and the final product so obtained employed in a pickling bath and tested in the manner described. The products referred to in the results set forth in Table I, as inhibitors A to G inclusive, represent the phosphoric acid derivatives of the sulfur dioxide reaction product of the following bases:

Oompozmd A.Anhydro formaldehyde aniline.

Compound B.-Reaction product of substantially three molecular proportions of butylaldehyde and substantially one molecular proportion of aniline.

Compound C.Reaction product of substantially three molecular proportions of acetaldehyde and substantially two molecular proportions of ortho-toluidine.

Compound D.Reaction product of substantially one molecular proportion of betanaphthylamine and substantially one molecular proportion of formaldehyde.

Compound E.Reaction product of substantially one molecular proportion of orthotoluidine and substantially three molecular proportions of butylaldehyde.

Uompo'u/nd F .Reaction product of substantially one molecular proportion of 2,4- diamido diphenylamine and substantially three molecular proportions of heptaldehyde.

Compound G.-Reaction product of sub stantially one molecular proportion of aniline and substantially three molecular proportions of heptaldehyde.

The following table shows the comparative loss in Weight when test pieces 3 x 4" of 30 gauge low carbon steel were pickled forty minutes in 6% sulfuric acid at 80 C.

252. COMPOSITIONS,

in the presence of one of the preferred inhibitors and in the absence of an inhibitor.

Table I W htl Weight Weight of Weight of mg Inhibiting comofinhibsteel strip steel strip g pound employed itor embefore after gj g ployed pickling pickling exposed Grams Grams Grams Grams Compound A 0.06 18. 562 18.098 0.0193 Compound B 0.06 18. 427 17. 629 O. 0333 Compound C 0 00 18. 032 17. 760 0. 0113 CompoundD 0. 06 17. 824 17. 700 0. 0052 Compound E 0.06 18. 837 17.220 0. 0674 Compound F 0.06 18.144 17.976 0.0070 Compound G 0.06 17. 951 17.823 0. 0053 None None. 17. 9% 10. 763 0. 2985 It is thus apparent from the data set forth that the preferred class of materials constitutes an important group of inhibitors, as in all the examples set forth wherein one of the preferred inhibiting compounds was incorporated in the pickle liquor, there resulted a metal saving of a large percentage of the loss in weight of the steel test strips that results when no inhibitor was employed.

It has been found that other ratios of phosphoric acid, sulfur dioxide and aldehydeamine than those hereinbefore set forth may be reacted and employed as inhibitors. Thus, substantially one molecular proportion of the aldehyde derivative of a Schitis base formed by reacting substantially three molecular proportions of acetaldehyde with substantially two molecular proportions of aniline has been reacted with substantially seven-tenths of a molecular proportion of sulfur dioxide, and the product so formed has been reacted with substantially twothirds of a molecular proportion of phosphoric acid. The compound thus produced was incorporated in a pickle liquor in the manner hereinbefore described. The amount of inhibitor used and the size and grade of steel sheets used was the same as in the above described tests. A sheet weighing 18.246 grams was found after pickling forty minu es to have lost but 0.302 grams, or 0.0126 grams per square inch of surface exposed. A sheet of the same stock weighing 17 .928 grams and treated in the same manner, but with no inhibitor present, suffered a loss of 7 .165 grams total weight or 0.2985 grams per square inch of surface exposed.

Although it is desirable that the preferred inhibitor be prepared in the presence of an organic solvent, as for example acetone, benzene and the like, it is not imperative that a solvent be employed. The sulfur dioxide may be reacted with the aldehyde amine product without dissolving the latter in a solvent, and the product so formed may be further reacted with phosphoric acid, forming a compound of the preferred type, which possesses the inhibiting qualities desired.

Other modes of employing inhibitors of the type set forth herein in the acid pickling of metals are apparent to those skilled in the art to which this invention pertains. The products described additionally may be employed in the pickling process in the presence of foaming agents, ionizable substances or other materials ordinarily used, as well as the different acids customarily employed in the pickling of various metals.

What is claimed is:

1. A process of pickling a metal which comprises subjecting the metal to be pickled to the action of a substantially non-oxidizing mineral acid solution containing a small proportion of a phosphoric acid derivative of a reaction product of sulfur dioxide and an aldehydc aimne product. 2. A proces o f pickling a metal which comprises subjecting the metal to be pickled to the action of a substantially non-oxidizing acid solution containing a small proportion of av phosphoric acid derivative of a reaction product of sulfur dioxide and an aliphatic aldehyde-aromatic amine reaction product.

3. A process of pickling iron and steel products which comprises subjecting the metal to be pickled to the action of a sulfuric acid solution containing a small proportion of a phosphoric acid derivative of a reaction product of sulfur dioxide and an aldehydeaniine product.

4. A process of pickling iron and steel products which comprises subjecting the metal to be pickled to the action of a. sulfuric acid solution containing a small proportion of a phosphoric acid derivative of a. reaction product of sulfur dioxide and an aliphatic aldehyde-aromatic amine reaction product.

5. A process of pickling iron and steel products which comprises subjecting the metal to be pickled to the action of a sulfuric acid solution containing a small proportion Limil'flli jl of a phosphoric acid derivative of a reaction product of sulfur dioxide and an aldehyde derivative of a SchitPs base.

6. A process of pickling iron and steel products which comprises subjecting the metal to be pickled to the action of a sulfuric acid solution containing a small proportion of a phosphoric acid derivative of a reaction product of sulfur dioxide and an aliphatic aldehyde derivative of a Schiffs base.

7. A process of pickling iron and steel products which comprises subjecting the metal to be pickled to the action of a sulfuric acid solution containing a small proportion of a phosphoric acid derivative of a reaction product of sulfur dioxide and a material formed by reacting an aliphatic aldehyde containing less than eight carbon atoms with a. primary aromatic amine.

8. A process of pickling iron and steel products which comprises subjecting the metal to be pickled to the action of a sulfuric acid solution containing a small proportion of a phosphoric acid derivative of a reaction product of sulfur dioxide and a material formed by reacting substantially three molecular proportions of acetaldehyde with substantially two molecular proportions of aniline.

9. A process of pickling iron and steel products which comprises subjecting the metal to be pickled to the action of a sulfuric acid solution containing a small proportion of a product formed by reacting substantially one-half a molecular proportion of sulfur dioxide with substantially one molecular proportion of the reaction product of substantially three molecular proportions of acetaldehyde and substantially two molecular proportions of aniline and further reacting the product thus formed with substantially one molecular proportion of phosphoric acid.

10. A process of pickling iron and steel products which comprises subjecting the metal to be pickled to the action of a. sulfuric acid solution containing a small proportion of a product formed by reacting in the presence of acetone substantially one-half a molecular proportion of sulfur dioxide with substantially one molecular proportion of the reaction product of substantially three molecular proportions of acetaldehyde and substantially two molecular proportions of ani line and further reacting the material thus formed with substantially one molecular proportion of substantially 85% phosphoric acid.

11. A pickling bath for metal products which comprises a substantially non-oxidizing mineral acid solution containing a small proportion of a phosphoric acid derivative of a reaction product of sulfur dioxide and an aldehyde-amine product.

12. A pickling bath for metal products which comprises a substantially non-oxidizing mineral acid solution containing a small proportion of a phosphoric acid derivative of a reaction product of sulfur dioxide and an aliphatic aldehyde-aromatic amine reaction product.

13. A pickling bath for iron and steel products comprising a sulfuric acid solution containing a small proportion of a phosphoric acid derivative of a reaction product of sulfur dioxide and an aldehyde-amine product.

14. A pickling bath for iron and steel products comprising a sulfuric acid solution containing a small proportion of a phosphor ic acid derivative of a reaction product of sulfur dioxide and an aliphatic aldehyde-aromatic amine reaction product.

15. A pickling bath for iron and steel products comprising a sulfuric acid solution containing a small proportion of a phosphoric acid derivative of a reaction product of sulfur dioxide and an aldehyde derivative of a Schifls base.

16. A pickling bath for iron and steel products comprising a sulfuric acid solution containing a small proportion of a phosphoric acid derivative of a reaction product of sulfur dioxide and an aliphatic aldehyde derivative of a Schiifs base.

17. A pickling bath for iron and steel products comprising a sulfuric acid solution containing a small proportion of a phosphoric acid derivative of a reaction product of sulfur dioxide and a material formed by reacting an aliphatic aldehyde containing less than eight carbon atoms with a primary amine.

18. A pickling bath for iron and steel products comprising a sulfuric acid solution containing a small proportion of a phosphoric acid derivative of a reaction product of sulfur dioxide and a material formed by reacting substantially three molecular proportions of acetaldehyde with substantially two molecular proportions of aniline.

19. A pickling bath for iron and steel products comprising a sulfuric acid solution containing a small proportion of a product formed by reacting substantially one-half a molecular proportion of sulfur dioxide with substantially one molecular proportion of the reaction product of substantially three molecular proportions of acetaldehyde and substantially two molecular proportions of aniline and further reacting the material thus formed with substantially one molecular proportion of phosphoric acid.

20. A pickling bath for iron and steel products comprising a sulfuric acid solution containing a small proportion of a product formed by reacting in the presence of acetone substantially one-half a molecular proportion of sulfur dioxide with substantially one molecular proportion of the reaction product of substantially three molecular proportions of acetaldehyde and substantially two molecular proportions of aniline and further reacting the material thus formed with substantially one molecular proportion of substantially 85% phosphoric acid.

In testimony whereof I hereunto aflix my signature.

DEAL H. TOMPKINS.