US1808184A - Cleaning and preserving of metallic surfaces - Google Patents

Description

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 PRESERVING OF METALLIC SURFACES No Drawing.

invention relates to the prevention of excessive pitting and embrittlement of a metal when subjected to a pickling process.

Certain objects of the invention are to pre- Vent 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 speed 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 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 analkaline bath to remove the last traces of free acid. The acid removes the rust and scale, but unfortunately, from the pickling standpoint, 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 line spray of the pickling bath and producing an atmosphere possessing corrosive properties 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 restrain the action of the acid from attacking clean metal but assists in removing the rust, scale and other deposits, or in other words'it selectively removes such materials without appreciably attacking the clean portions of the metal.

The pickle regulator or inhibitor, as disclosed in the present application, comprises a sulfuric agidderilative of a reaction product oisuldioxide and an aldehyde-amine re- Application filed June 30,

1930. Serial No. 465,070.

action product and preferably a sulfuric, acid derivative of a reaction product of sulfur dioxideland an aldehyde derivative of' a Schifis base; that is, a product formed by reacting an aldehyde with a Schifi"s base, adding sulfur dioxide thereto and treating the-product so formed with sulfuric acid of any concentration necessary to produce sulfonation at the reaction temperature employed.

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

Test pieces of steel approximately 4 x 3", gauge hot rolled tin plate stock were then immersed in approximately 500 c. c. ofa water solution of sulfuric acid containing approximately 8% by weight of 66 B. 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 C.). For the acid concentration set forth, commercial practice is to pickle at approximately 150 to 190 F. (66 to 88 (3.). 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 sulfuric acid derivative of the reaction product of sulfur dioxide and an aldehyde derivative of a Schiifs base, was prepared as 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 C. To the product thus formed, substantially one molecular proportion of sulfuric acid, preferably having an acid strength of 75% was added at a temperature of substantially 50 to C. After the addition of the sulfuric 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, after cooling'was a brittle resin, which formed a fine powder when ground that was readily soluble in a pickle liquor as for example dilute sulfuric acid. A 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 hot rolled tin plate stock, exposing 24 square inches of surface and weighing 17.5228 grams, was found to lose but 0.017 3 grams after 20 minutes pickling in an 8% sulfuric acid solution containing 0.12 grams of the inhibiting product just described. A similar test piece weighing 17.0100 grams and treated in the same manner, but without the use of any inhibitor lost 0.2997 grams.

Thus, when the sulfuric acid derivative of the reaction product of sulfur dioxide and the product formed by reacting substantially three molecular proportions of acetaldehyde and substantially two molecular proportions of aniline is employed as an inhibitor, the loss in weight per square inch of surface exposed corresponds to 0.00072 grams whereas when no inhibitor is used the loss per square inch of surface exposed corresponds to 0.0125 grams. A 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 not stained upon removal from 60 to 70 C. To the product so formed approximately one molecular proportion of sulfuric acid having an acidity of approximately was added with agitation at a temperature of approximately 90 to 100 C. A sample of the above identified material was incorporated in a sulfuric acid pickling bath in the manner previously described. The following table shows a comparison between the loss in weight of the test strips, after immersion in the pickling bath for twenty minutes, when the inhibitor just described was employed and when no inhibitor was employed.

Table I 3" x 4", 30 gauge hot rolled tin plate stock pickled twenty minutes in 8% sulfuric acid at C.

Average loss with inhibitor 0.000391 grams per sq. in.

Average loss without inhibitor 0.012491 grams per sq. in.

From the results set forth in Table I it is apparent that the average loss in weight when no inhibitor is employed is approximately thirty-four times greater than the average loss resulting when the inhibitor set forth is employed in the pickle bath described.

Other sulfuric acid derivatives of the reaction products of sulfur dioxide and aldehyde-amine products, and preferably sulfuric acid derivatives of the reaction products of sulfur dioxide and aldehyde. derivatives of Schifi"s 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 sulfuric acid derivatives of the sulfur dioxide reaction products of a Schiifs base and of aldehyde derivatives thereof as set forth hereinafter were prepared and the final product so obtained empolyed in a pickling bath and tested in the manner described. The products referred to in the results set forth in Table II, as inhibitors A to G inclusive, represent the sulfuric acid derivatives of the sulfur dioxide reaction product of the following bases:

Oompownd A.Substantially three molecular proportions oftacetaldehydeaiid two molecular proportions of orthgtoluidine.

252. COMPOSITIONS,

ular proportions of butylalglebyde and one molecular proportion of ortho-toluidine.

Table II 3 x 4", 30 gauge hot rolled tin plate stock pickled twenty minutes in 8% sulfuric acid at 80 C.

' i w h r w in f 'eig to eig of oss in gh gai -Ea steel strip steel strip grams per poun mp 0y em 10 ed before after sq. inch of p y pickling pickling surface exposed I Grams Grams Grams Grams Compound A. O. 12 16. 672 16:655 0. 00071 Compound B- 0. 12 16. 810 16. 798 0. (-0050 Compound C- 0. 12 17. 342 17. 336 0. 00025 Compound D. 0. 12 17. 122 17. 101 0. 00087 Compound E... .12 16. 655 16. 649 0. COCZS Compound F. 0. 12 17. 503 17. 496 0. 00029 Compound (3.. 0. 12 16. 620 16. 604 0. 00058 None l None. 17.0100 16. 7103 0. 01242 It is thus apparent from the data set forth that the preferred class of materials constitute an important group of inhibitors, as in all cases where one of the preferred inhibiting compounds was incorporated in the pickle liquor, there resulted a metal saving of from 96 to over 98% of the loss in weight of the steel test strips that resulted when no inhibitor was employed.

The preferred class of inhibiting compounds has also been employed in other pickling baths than sulfuric acid wherein materials 0' her than iron and steel were pickled. The following example illustrates one method of pickling a nickel chromium alloy, wherein one of the preferred inhibitors, for example, the product formed by treating the reaction product of sulfur dioxide and the aldehyde-amine product prepared from substantially three molecular proportions of acetaldehyde and substantially two molecular proportions of aniline with sulfuric acid in the manner previously described, was employed as an inhibitor in a hydrochloric acid pickling bath.

A piece of nickel chromium alloy wire having a composition of 80% nickel and 20% chromium, 36 inches in length, 0.036 inches in diameter, having a total surface of 4.07

Hammer square inches and weighing 5.2640 grams, was coiled in the form of a spiral and immersed in approximately 500 grams of 17% hydrochloric acid containing 0.24 grams of the product formed by treating the reaction product of substantially three molecular proportions of acetaldehyde and substantially two molecular proportions of aniline with sulfur dioxide and further reacting said prouct with sulfuric acid in the manner hereinbefore described. After allowing the wire to, remain in the pickle liquor for 20 minutes at 176 F., the loss in weight was found to be only 0.0405 grams. A test identical with that described above with the exception that the nickel-chromium wire weighed 5.3225 grams and no inhibitor was employed, showed a loss of 0.2060 grams. words the weight loss due to solvent action of the hydrochloric acid on the metal was only one-fifth as great when the preferred inhibitor was employed as was the loss with no inhibitor present. A greater saving in metal would be realized by employing a greater proportion of the inhibitor.

It has further been found that other ratios In other of sulfuric 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 Schiifs base formed by reacting substantially three moleoular proportions of acetaldehyde with substantially two molecular proportions of aniline has been reacted with varying amounts of sulfur dioxide preferably in the ratios between substantially one-fifth to one molecular proportion and the material so prepared further reacted with varying concentrations of sulfuric acid preferably in ratios varying between three-fourths to one and one-half molecular proportions. In all cases the materials so obtained, on incorporating in a pickle bath and testing in the manner hereinbefore set forth, were found to be very prepared in a benzene medium and the resulting material on testing found to be a very desirable inhibitor.

Other modes of employing inhibitors of the type set forth herein in the acid pickling of metals are apparent to those skilled in the 3;:

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.

\Vhat is claimed is: 1. 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 sulfuric acid derivative of a reaction product of sulfur dioxide and an aldehydeamine product.

2. 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 sulfuric 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 prodacts which comprises subjecting the metal to be pickled to the action of a sulfuric acid solution containing a small proportion of a sulfuric acid derivative of a reaction product of sulfur dioxide and an aldehyde derivative of a Schiffs base.

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 sulfuric acid derivative of a reaction product of sulfur dioxide and an aliphatic aldehyde derivative of a Schiffs base.

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 of a sulfuric 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.

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 sulfuric 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.

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 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 sulfuric acid.

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 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 75% sulfuric acid.

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

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

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

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

13. A pickling bath for iron and steel products comprising a sulfuric acid solution containing a small proportion of a sulfuric 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.

14. A pickling bath for iron and steel products comprising a sulfuric acid solution containing a small proportion of a sulfuric 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.

15. A pickling bath for iron and steel products comprising asulfuric 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 sulfuric acid.

16. 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 propor- .252. COMPOSITIONS,

tion 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 sulfuric acid.

17 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 sulfuric acid derivative of a reaction product of sulfur dioxide and an aldehyde-amine product.

18. A process of 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 a sulfuric acid derivative of a reaction product of sulfur dioxide and an ali hatic adlehyde-aromatic amine reaction pro uct.

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

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

In testimony whereof I hereunto aflix my signature.

DEAL H. TOMPKINS.