US1817500A - Treating metals and compositions therefor - Google Patents

Description

252. COMPOSITIONS,

Patented Aug. 4, 1931 UNITED STATES Examiner PATENT OFFICE JAMES C. VIGNOS, OF NITRO, WEST VIRGINIA, ASSIGNOR TO THE RUBBER SERVICE LABORATORIES COMPANY, OF AKRON, OHIO, A CORPORATION OF OEIO TREATING METALS AND COMPOSITIONS THEREFOR No Drawing.

The present invention relates to the cleaning and preservation of metallic surfaces wherein the surface is in contact with liquids of an acid nature. More particularly. the invention relates to the prevention of excessive pitting and embrittlcmeni of metals when subjected to av pickling process. The invention includes the provision of a regulator or inhibitor for causing the acid solution selectively to attack unclean portions of metallic surfaces immersed therein to the substantial exclusion of any corrosive action upon clean portions of the metal surface.

In the art of pickling, the metal is treated with a dilute acid to remove rust, scale or other deposits. The acid solution removes the rust and scale, but in the absence of any material preventing such action, also attacks clean portions of the metal, thereby causing pitting or other pickling of portions of the metallic surface. Such pitting is particular- 1y detrimental and undesirable when the metal is to be plated, painted or galvanized and cold worked.

By means of the present invention the ob jectionable features of the pickling process are substantially overcome and eliminated. To accomplish this in accordance with the present invention, there is added to the pickling bath or other acid solution employed, a regulating agent or ingredient which acts to restrain the action of the acid in removing the scale or deposit. or in other words, the ingredient causes the acid selectively to re move oxides and the likewithout materially attacking the clean portions of the metal surface.

The regulators or inhibitors which are disclosed in the present application comprise organic sulphur-containing compounds of a type wherein one or moresulphur atoms are joined preferably to one or two carbon atoms. The preferred type of compounds are organic sulfide, disulfids and .polysulfids of bothopen chain and ring structure. Compounds of the type preferred, as hereinafter set forth, comprise particularly materials containin a grouping such as -G-S S; or -G ,-C or other groupings contain- Serial No. 246,917.

ing carbon and sulphur, such as --C=S wherein the carbon joined to the sulphur atom is linked to carbon or other atoms other than to more than one atom of nitrogen.

The invention will be readily understood from the following description and examples. In the examples 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. The heating of the metallic test strips in the pickling liquor, in the manner as hereinafter set forth was, however, from three to four times that ordinarily followed in practice for the acid concentrations employed. Test pieces of steel approximately three inches square were cut from a sheet after the annealing process had been carried out.

tion of the pickle liquor for approximately an hour while being maintained at a temperature of from 176 to 185 F. to C.). For this acid concentration, commercial practice is to pickle at approximately F. (73.8 C.) for from 15 to 20 minutes. In all cases, the results were compared with similar tests wherein the steel pieces were subjected under the conditions set forth to the action of an acid solution of 95 the strength speclfied above, but containlng no inhibitor. Comparison of the loss in weight suffered by the various test pieces give at once a measure of the inhibiting action exerted by the compounds tested.

Thus, when meroaptohenzoa-thiazolmdis ,sulfid possessing the formula was employed under the conditions set forth and in the proportion of approximately 0.01% of the weight of acid solution used, it was found that the loss in weight suffered by the iron was only 1/10 as great as the loss ensuing when no inhibitor was present in the pickle bath.

In another test carried out in the manner hereinbefore described, a quantity of benzykdisnlfid, (C H .CH S equal to but 1/500 of 1% of the quantity of acid solution taken, was employed as an inhibitor. It was found that the presence in the acid solution of such a very small proportion of inhibitor resulted in a pickle sheet of good appearance that had lost less'than 1/16 as much weight as that lost by pickling in an acid solution of the same strength but containing no inhibitor.

Benzyl-disulfid when addedto the pickle liqfii'insmall prgportionsjin a solution employing furfural or phenol as a solvent gave equally good results both in p'ickling steel and copper sheets. Likewise the same compounds, either alone or in conjunction with the solvents mentioned produced an equally desirable effect when hydrochloric acid was employed in a pickle bath for treating steel and copper.

Other aromatic sulfids have also been found to exert an inhibiting action in the pickling process. Thus -sulfid and dinitro-diphenyl-disulfid are effective in the process described. Likewise i phenyl-disulfid and,.p-p-diaminosbenzvl-di sulfid wheii iised in the proportion 0 approximately 1/500 of 1% of the weight of acid solution taken resulted in a saving of at least 90% of the loss that took place when no inhibitor was present in the acid solution.

Aliphatic mono and disulfid compounds have also been found to possess desirable characteristics as inhibitors of the action of acids upon metal surfaces. Thus allyl-sulfid iso-amyl-mono and disulfids, ethyhdi sulfid heta-heta lihydroxy-thifl saifid and other like compoms-have'all beenfiund to exert an inhibiting action on acids emploved in a metal pickling bath. Allylsultid for example which is a typical representative of the class of aliphatic sulfids mentioned, when employed in the roportion of approximately 1/500 of 1% of the quantity of acid solution taken in the process as hereinbefore described was found to diminish the quantity of dissolved metal to only about l/l0 of that resulting when no inhibitor was employed. As in the case of the other compounds mentioned the inhibiting action of the materials is increased by the use of a larger proportion of the compounds than is set forth in the example.

Other types of sulphur-containing compounds useful in the process as herein set forth are the di.-.thioc a rb a m i c acids and their metallic and pgganic salts, The organic salts of such cofiiaaams' are readily obtained by eaqting carbon bisuliid upon sec; ondary aminesfpar'ticularly secondary aliph'zitic "amines. Thus, piperidine-penta- 'inethylen-di thiocarbamate was employed in th'e'pfo'cess'hereinbefore set forth in the proportion of 0.01 of 1% of the quantity of acid solution employed. The iron loss resulting from carrying out the pickling process in the presence of this inhibitor of acid action was found to be approximately 7.5% of that resulting when no inhibitor was employed. In other words, the presence of such a slight proportion of this type of inhibitor resulted in a saving of approximately 13/14 of the loss that followed from the use of no inhibiting compound. Such a small loss per square inch of surface would be practically negligible since in the example given, the loss amounted to only 0.0015 gram of each square inch of metal exposed to the acid solution. Other..di -thiooa rb amates, containipgihq: grouping, where X geipresents hydrogen or an organic group, are lEWlSG effective for use 'in the process described.

Ihima1 1- I11On0 and disulfids which c011- tain the grouping respectively are also effective for preventing the excessive deterioration of metals immersed in or subjected to the action of an acid solution. Thus, a solution was prepared for use in pickling metals comprising 500 cc. of sulphuric acid containing approximately 8% by weight of 66 Baum acid. To this acid solution there was added The resulting solution contained approximately 0.002% of the disulfid. Iron test strips were then immersed in the solution for about 60 minutes while maintaining the solution at a temperature of from 80 to 85 C. The loss in weight of the test strips resulting from exposure to the pickling solution was observed to be only about 7.5% of the loss that resulted when a similar test strip was pickled under the same conditions in an acid solution containing no inhibitor. That is, the inhibitor decreased by about 13/14 the metal loss due to solvent action of the acid on the metal. This loss 252. COMPOSITIONS,

when calculated on the surface exposed to the solution amounted to but 0.00155 gram per square inch of surface.

A similar test carried out in the manner as described, except that di-methyl-alp hanaphthyl thiuram disulfid was employed in pI'a'ceWf-the'inhibitof's'pecified in the example, yielded a result showing that the solvent action of the acid on the metal was decreased by approximately 12/13. In other words, the loss in metal per square inch of surface exposed to the acid solution was only 0.0013 gram as compared with a loss of 0.0172 gram per square inch where no inhibitor was employed.

A further test was completed wherein 31;;

(fiflllldii-tOlYl thiuram disulfid was employed as an inhibito fi'fi'tlie iiianner as described. An acid solution of the strength mentioned and containing only 0.002% of the inhibitor was found to be particularly effective for the objectdesired. Such a solution was found to pickle iron and steel strips in such a manner that the acid loss due to solvent action of the acid was only 3.8% as great as that taking place when no inhibitor was employed. This loss, distributed over the area of surface exposed to the pickle solution, amounted to only 0.00000 gram per square inch as compared with a loss of 0.01722 gram per square inch when no inhibitor was employed.

Other thiuramsulfids have also been found to possess a desirableTnhibiting effect when employed in quantities comprising less than 1% of the pickle solution. Tests similar to those hereinbefore set forth have been carried out wherein di=ethyl-.d i- )lien l thim:am ii lllfidsfilllyl.ill llli BIQE OHIMUEQQY .tl1iuram di sulfid and the lilfe were employed as inhibitors and found to retard the action of acid upon a metal.

By proceeding in a like manner, similar beneficial effects were ascertained to be exercised when thiuram disulfids were employed in a pickle liquor comprising hydrochloric acid. Other metals, such as copper and the like were also protected from undue corrosion by acids when the preferred type of inhibitors were employed in the pickling liquor. It is evident from the various examples hereinbefore set forth, that organic sulfids, disulfids, and polysulfids comprise a class of effective inhibitors in processes wherein metals are subjected to the action of an acid. Greater inhibiting action has been found to be produced by the use of a larger quantity of the various compounds than that set forth in the examples. It is not, however, necessary to employ an acid solution containing more than 1% by weight of the inhibiting compound, nor is it desirable to use a greater quantity than will completely dissolve in the solution employed.

The examples hereinbefore set forth are Examiner to be understood as illustrative only and not at all limitative of the scope of the invention. Other examples of the process described are apparent to those skilled in the art to which the invention pertains wherein different acid concentrations, times of treatment and temperatures may be employed. The invention is to be considered as limited solely by the following claims wherein the invention is claimed as broadly as is possible in view of the prior art.

What 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 an aromatic disulfid compound.

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 benzyl-disulfid.

3. A pickling bath for iron and steel products comprising sulphuric acid containing more than 0.01% but less than 1% by weight of an organic disulfid compound free of amino substituents.

4. A pickling bath for iron and steel products comprising sulphuric acid containing more than 0.01% but less than 1% by weight of an aromatic disulfid compound.

5. A pickling bath for iron and steel products comprising sulphuric acid containing more than 0.01% but less than 1% by weight of benzyl-disulfid.

6. A metal treating compound comprising a sulfuric acid solution of an aromatic disulfid.

7. A metal treating compound comprising a sulphuric acid solution of benzyldisulfid.

8. A pickling bath for metals containing an aryl disulfid compound;

9. A pickling bath for metal containing benzyl disulfid.

In testimony whereof I hereunto afiix my signature.

JAMES C. VIGNOS.