US1932553A - Cleaning and preservation of metallic surfaces - Google Patents

Description

l. UUIYH'UDI HUNG,

reti ed Patented Oct. 31, 1933 UNITED STATES 1,932,553 PATENT OFFICE CLEANING AND PRESERVATION OF METALLIC SURFACES George L. Magoun, Nitro, W. Va., assignor to The Rubber Service Laboratories Compam", Akron, Ohio, a corporation of Ohio No Drawing. Application January 19, 1931 Serial No. 509,884

8 Claims.

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 ametal when subjected to a pickling process by treatment with a dilute solution of a non-oxidizing acid.

Certain objects of the present 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 efiiciency of the pickling operation; 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 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 present, it g ttacks the cleaned metal itself, thereby .causin l ss of metal and producing an evolution of hydroge'n'gas, which escapes into the air, carrying with it a fine spray of the acid liquor from the pickling bath and producing an atmosphere possessing corrosive properties and one which is injurious to health and damaging to equipment.

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 facilitates the removing of rust, scale and other deposits, or in other words the regulator or inhibitor causes the acid selectively to remove such materials without appreciably attacking the clean portions of the metal under treatment.

The pickle regulator or inhibitor, as disclosed in the present application, comprises a reaction product of a fully saturated organic base and a mercaptoarylthiazole.

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 employed.

Test pieces of 30 gauge cold rolled tin plate steel stock, approximately 4" x 3" in dimension, were immersed in approximately 750 c. c. of a water solution of sulfuric acid containing approximately 6% 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 80 to 85 C. For the acid concentration set forth, commercial practice is to pickle at approximately 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 of the preferred class of compounds, for example, a reaction product of hexamethylene tetramine and 2-mercaptobenzothiazole, was prepared by placing approximately 175 parts by weight of hexamethylene teiramine and approximately 313 parts by weight of Z-mercaptobenzothiazole in a suitable vessel, mixing and heating the contents to a temperature of approximately 90 to 135 C.

A sample of the product prepared as described above was incorporated in a pickling bath in the manner hereinbefore described. Thus, a steel test piece, 3" x 4 in dimension, cut from 30 gauge cold rolled tin plate stock, exposing approximately 24 square inches of surface and weighing 18.230 grams, was found to lose but 0.019 grams after 40 minutes pickling in 750 c. o. of a 6% sulfuric acid solution containing 0.047 grams of the inhibiting product hereinbefore described. A similar test piece weighing 18.738 grams and treated in the same manner, but without the use of any inhibitor lost 0.541 grams. Thus it is shown that when the reaction product of hexamethylene tetramine and Z-mercaptobenzothiazole is employed as an inhibitor, the loss in weight per square inch of surface exposed corresponds to 0.00079 grams, whereas when no inhibitor is employed in the test described, the loss per square inch of surface exposed corresponds to 0.0225 grams. The loss in weight per square inch of surface exposed is only 3.5 per cent as great by employing the inhibitor set forth as results if no inhibitor is employed in the pickling process. A greater saving in metal losses results from the use of a larger amount of the inhibitor than that employed in the example. Moreover, the steel plates pickled in the presence of the inhibitor set forth are clean and not stained upon removal from the bath.

Other mercaptoarylthiazole derivatives of saturated organic bases have been prepared and tested. Thus the following reaction products have been prepared and tested in a manner analogous to that hereinbefore set forth. With the exception of compounds E and F, the methods for the preparation of which are given below, the following reaction products were prepared in a manner analogous to that hereinbefore described for the preparation of the reaction product of hexamethylene tetramine and mercaptobenzothiazole.

Compound A.--Reaction product of substantially one molecular proportion of Z-mercaptobenzothiazole and substantially one molecular proportion of diethylamine.

Compound B.Reaction product of substantially one molecular proportion of 2-mercaptobenzothiazole and substantially one molecular proportion of triethanolarnine.

Compound C.-Reaction product of substantially one molecular proportion of Z-mercaptobenzothiazole and substantially one molecular proportion of pyrrolidine.

Compound D.-Reaction product of substantially one molecular proportion of Z-mercaptobenzothiazole and substantially one molecular proportion of pipgridine.

CompoundE-l-teaction product of substantially two molecular proportions of 2-mercapt0- benzothiazole and substantially one molecular proportion of acetaldehyde-ammonia. (The reaction was accomplished in this case by heating the mixture of the reactants at approximately 150 to 160 C. for a period of approximately two hours.)

Compound F.-Reaction product of substantially one molecular proportion of bis-mercapto benzothiazole and substantially two molecular proportions of tributylamine. (The reaction was accomplished in this case by heating the reactants in an alcoholic solution.)

The results of the tests obtained on immersing steel test strips of 30 gauge cold rolled tin plate stock, 3" x 4" in dimension, for 40 minutes in 750 c. c. of 6% by weight of 66 B. sulfuric acid at C., in the presence of 0.04? grams of one of the above described inhibitors, are given in Table I.

Table I W ight 10$ Inhibiting Weight of 229 in grams per compound inhibitor i p square inch of employ ed employ ed Diem-m" pickling Grams Grams Grams Grams Compound A 0. 047 18. 7'. 18. 762 0. 00042 Compound 13 0. (ii? 18. T75 18. 763 0. 00050 Compound C 0. 047 i8. 305 18.266 0.00103 Compound D. 0.047 18.905 18.865 0.00l67 Compound E- 0. 0 .7 17.448 14. 429 0. 00079 Compound F 0. 47 18.606 i8. 563 0.00175 None None. 18.738 18.197 0.02254 It is thus apparent from the data set forth that the preferred class of materials constitutes an important and highly efiicacious group of inhibitors, as in all cases wherein one of the preferred inhibiting compounds was incorporated in the pickle liquor there resulted a great saving in the loss in weight of the steel test strips as compared with that resulting when no inhibitor was employed.

As a further example of operating the present invention, the reaction product of substantially one molecular proportion of Z-mercaptobenzothiazole and substantially one molecular proportion of morpholine was prepared and tested in the pickling bath as an inhibitor in the manner hereinbefore described, and it was found to possess the inhibiting qualities of the preferred class of compounds.

In like manner, other fully saturated organic bases, such as diethanolamine. cyclohexylamine, ethanolarnine, diacetone-amine, and propylamines, may be reacted with mercaptobenzothiazoles, mercaptotolylthiazoles, and the like and the product so obtained employed as inhibitors.

Other modes of employing inhibitors of the class hereinbefore set forth 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 presence of foaming agents, ionizable sub stances or other materials ordinarily used, and are employable with the various acids commonly employed commercially in the acid pickling of metals.

What is claimed is:

l. 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 reaction product of a fully saturated aliphatic amine and a mercaptobenzothiazole.

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 reaction product of a fully saturated aliphatic tertiary amine and a mercaptobenzothiazole.

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 reaction product of hexamethylene tetramine and 2-mercaptobenzothiazole.

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 the product formed by reacting substantially 175 parts by weight of hexamethylene tetramine with substantially 313 parts by weight of Z-mercaptobenzothlazole.

5. A pickling bath for iron and steel products which comprises a sulfuric acid solution containing a small proportion of a reaction product of a fully saturated aliphatic amine and a mercaptobenzothiazole.

6. A pickling bath for iron and steel products which comprises a sulfuric acid solution containing a small proportion of a reaction product of a fully saturated aliphatic tertiary amine and a mercaptobenzothiazole.

7. A pickling bath for iron and steel products which comprises a sulfuric acid solution containmg a small proportion of a reaction product of hexamethylene tetraminc and 2-mercaptobenzotbiazole.

8. A pickling bath for iron and steel products which comprises a sulfuric acid solution containing a small proportion of the product formed by reacting substantially 175 parts by weight of hexamethylene tetramine with substantially 313 145 parts by weight of Z-mercaptobenzothiazoie.

GEORGE L. MAGOUN.

CERTlFlCATE OF CORRECTION. October 31, 1933.

'Patent No. 1,932,553.

GEORGE L. MAGOUN.

It is hereby certified that error appears in the printed specificntion of the above numbered patent requiring correction as follows: Page 2, line 59, column for "0.47" read 0.047; and that the said Letters Patent should .2, of Compound F,

hat the same may conform to the'r'ccord of be read with this correction therein t the case in the Patent Office.

Signed and scaled this 12th day of December, A, D. 1933.

i. M. Hopkins (Seal) Acting Commissione of Patents.