US2050354A - Pickling of metal - Google Patents

Description

Aug. 11, 1936 Patented UNITED STATES PATENT OFFICE PICKLING OF METAL No Drawing. Application September 8, 1935, Serial No. 38,948

13 Claims. (01. 148-8) This invention relates to the acid pickling of metal, more particularly to pickling ferrous metals in dilute sulfuric acid solution.

It is among the objects of this invention to provide a method of pickling and an inhibitor therefor which aflord eflicient pickling and inhibiting, in the use of which satisfactorily uniform inhibiting action throughout the use of a given bath is attainable by periodic additions of inhibitor to the bath, in which uniformity of inhibiting action from bath to bath is readily obtainable. A particular object is to provide an inhibitor which avoids scum formation, is relatively cheap and is accurately reproducible, is efficient in inhibiting power, and which is not liable to be decomposed by the heat encountered through the methods commonly applied for heating pickling baths.

A further object is to provide a method of pre- 0 paring inhibitors embodying the foregoing characteristics.

I The present invention is predicated upon our discovery that its stated objects are attained with an inhibitor made by sulfonating an hydroxylic 25 organic compound such as a phenol or an alcohol,

a d a mustard oil or a substituted thiogrgg.

examples of the hydroxylic compounds which may be used in the practice of the invention, we have obtained satisfactory results with 30 such substances as phenol, cresols, especially in the form of crude creosote,'ethyl alcohol, glycerin, and sulfonated castor 011. As to mustard oils and substitution products of thiourea, we have made highly satisfactory inhibitors embodying the de- 35 sirable features which characterize this invention from phenyl and diphenyl thiourea, phenyl mustard oil, and allyl mustard oil, which are typical of this constituent of the reaction mixture. The mustard oils may be said to possess the type for- 40 mula RNCS, in which R may be an alkyl or an aryl group. The substituted thioureas may be said to possess the type formula in which R and R1 are amino or substituted amino groups. Compounds of the latter type yield products of the former type upon treatment with con- 50 centrated sulfuric acid.

In the practice of the invention the materials designated are subjected to sulfonation, for example by mixing them with 60 to 66 B. sulfuric acid. while w'do not understand exactly what 55 reaction occurs, we now believe that the constituents react to produce a new chemical identity which then undergoes sulfonation. We do not, of course, limit ourselves to that theory, and whatever be the nature of the change which occurs, such products provide unusually efficient 5 and desirable pickling inhibitors. For instance, very low concentrations of the inhibitors provided by this invention suiiice to afford satisfactory inhibition, and the inhibitors appear to be comparatively stable to the various actions 10 which may, and in many instances do, cause deterioration of the inhibitors used previously.

The inhibitors provided by this invention do not cause scum, and for the most part they are relatively cheap to make, and pickling costs are low 1 in any event because of the very low concentrations of inhibitors which suffice to provide satisfactory pickling conditions. In addition, the inhibitors of this invention represent materials of rather definite character and they are readily reproducible, and it is therefore possible to attain uniformity of pickling action from bath to bath. Another desirable feature is that by periodic additions of the inhibitor to the bath, as need be, uniform pickling action is achieved, a result not always attainable with other inhibitors.

The proportions in which the inhibitor-forming constituents are used will depend, as will be understood, upon the particular hydroxyllc compound and mustard oil, or substituted thiourea, used. By way of illustration, however, satisfactory results have been had using the proportions of 1 mol. of thiocarbanilide to 2 mols. of ethyl alcohol, phenol, or cresol. When using creosote we have found it fully satisfactory in calculating amounts to be used to consider it as being pure cresol. Likewise, we have had satisfactory results using one-fifth mol. of sulfonated castor oil per mol. of phenyl mustard oil or of thiocarbanilide. The proportions may, of course, be varied from those just stated.

The invention also provides a convenient method of preparing the inhibitors in an unusally effective and desirable form. In accordance with so controlled that the temperature does not become excessive, and usually it is desirable to keep the temperature below about 100 F. In

separate container the remaining portion of 6 the hydroxylic compound is mixed with the mustard oil or substituted thiourea to form a thin I aste which is then added to the acid reaction ture just described, the same conditions being observed. When all of the pasty material has 1 been added the preparation of the inhibitor is complete.

This method is readily controlled, can be carried out in simple and inexpensive apparatus, and it provides the inhibitor in a liquid form which 15 is readily handled and can be measured easily for proper dosage of the pickling bath.

In the practice of the invention the inhibitor is added to a solution of strong "1 for pickling errous metals. Low concentrations of the inhibitors provided by this invention sufiice, and our work has shown that for pickling both low and high carbon steels in an 8 percent solution of sulfuric acid at tempera- 25 tures up to 180 F., a concentration of about 0.04

'per cent is satisfactory. Most suitably the ino the con p or to rm n| pickling ferrous metal articles.

As illustrative of the benefits to be derived from the invention, reference may be made to tests showing the eilicacy of these inhibitors. In these tests the pickling bath comprised 230 cc. of a utility for g 35 7.6 per cent solution of sulfuric acid at a temperature of 150 F. The inhibitors listed in the following table were prepared in accordance with the method justdetailed; 0.1 cc. of the inhibitor was added to the"pickle bath. The material 40 pickled was cold rolled, low carbon strip about 0.005 inch thick made from a steel containing about 0.1 per cent of carbon; the strip was cut to form rectangles 3 x 1.5 inches. The samples were preliminarily cleaned, dried, and weighed. 45 After immersion for 30 minutes in the pickling bath they were again cleaned and\dried, and the weight loss was determined. For comparison identical tests were made using an identical pickling bath without inhibitor, and also iden- 50 tical baths containing a well-known commercially used inhibitor. The results were: as follows:

Average weight Comparable results were obtained also with 65 high carbon steel.

From the foregoing tests it appears clearly that the inhibitors provided by the present invention very substantially reduce the action of the pickling bath on the metal, and that the weight loss 70 is approximately half that obtained with the commercial inhibitors referred to.

The use of higher concentrations of these inhibitors than those used in the tests, for instance in amounts of 1 cc. per 230 cc. of pickling solu- 75 tion, appears to have no material effect in improving the inhibiting action, showing that very small amounts indeed sumce for many purposes.

Without restricting ourselves, we now believe that in the production of these inhibitors there occurs a reaction by which there is formed a sub- 5 stance of the following type formula in which R, R1, and B: may be a hydrogen, an

alkyl, an aryl, or a substituted aryl group. We now believe, although we do not limit ourselves to this theory, that hen substituted thloureas are used in thanractice o 'thifivenon 1 by thfin ulfonating medium with fdrma'tiUlTUTT such as phenyl' case of arbanilide, and that it is that mustard oil which is e ac.t ive c ns 1 W compound, in r nnibitcTrT (recording to the provisions of the patent statutes, we have explained the principle of our invention, and have described what we now consider to be its best embodiment. However, we desire to have it understood that, within the scope of the appended claims, the invention may be practiced otherwise than as specifically described.

We claim:

1. That method of pickling metal in a strong mineral acid bath comprising subjecting said metal to a bath of said acid containing a small amount of a product obtained by sulfonating a mixture of an organic hydroxylic compound and a substance of the group mustard oils and substituted thioureas.

2. That method of pickling metal in a strong mineral acid bath comprising subjecting said metal to a bath of said acid containing a small amount of a product obtained by sulfonating a mixture of a substance of the group phenols and alcohols, and a substance of the group mustard oils and substituted thioureas.

3. That method of pickling metal in a strong mineral acid bath comprising subjecting said metal to a bath of said acid containing a small amount of a product obtained by sulfonating a mixture of a substance of the group phenols and alcohols, and a substance of the group mustard oils and organic compounds producing mustard oils in the presence of strong sulfuric acid.

4. That method of pickling ferrous metal comprising subiecting said metal to a bath of dilute sulfuric acid containing a small amount of a product obtained by sulfonating a mixture of a substance of the group phenols and alcohols, and a substance of the group mustard oils and substituted thioureas.

5. That method of pickling ferrous metal comprising subjecting said metal to a bath of about 8 per cent sulfuric acid heated to about 150 F. and containing a small amount of a product obtained by sulfonating a mixture of a compound of the group phenols and alcohols, and a substance of the group mustard oils and substituted thioureas.

6. That method of pickling metal in a strong mineral acid bath comprising subjecting said metal to a bath of said acid containing a small amount of a product obtained by sulfonating a mixture of ethyl alcohol and a mustard oil or a substance producing mustard oil in the presence of strong sulfuric acid.

'1. That method of pickling metal in a strong 75 252. COMPOSITIONS,

mineral acid bath comprising subjecting said metal to a bath of said acid containing a small amount of a product obtained by sulfonating a mixture of phenol and a mustard oil or a substance producing a mustard oil in the presence of strong sulfuric acid.

8. That method of pickling metal in a strong mineral acid bath comprising subjecting said metal to said bath containing a small amount of a product obtained by sulfonating a mixture of (1) an organic hydroxyl compound of the group phenol, cresol, creosote, glycerin, and sulfonated castor oil, and (2) a substance of the group phenyl thiourea, diphenyl thiourea, phenyl mustard oil and allyi mustard oil.

9. That method of pickling ferrous metal in a bath of dilute sulfuric acid, comprising subjecting said metal to said bath containing a small amount of a product obtained by sulfonating a mixture of (1) an organic hydroxyl compound of the group phenol, cresol, glycerin, and sulfonated castor oil, and (2) a substance of the group phenyl thiourea, diphenyl thiourea, phenyl mustard oil and allyl mustard oil.

10. That method of pickling ferrous metal comprising subjecting said metal to a bath of about 8 per cent of sulfuric acid containing a small amount of a product obtained by sulfonating a mixture of (1) an organic hydroxyl compound of the group phenol, cresol, glycerin, and sulfonated castor oil, and (2) a substance of the group phenyl thiourea, diphenyl thiourea, phenyl mustard oil and aliyl mustard oil.

11. That method of pickling metal in a strong mineral acid comprising subjecting said metal to an acid pickling bath containing a small amount of a product obtained by sulfonating a mixture of an organic hydroxyl compound and a compound of the type formula cs 1 in which R and R1 are amino or substituted amino groups.

12. That method of pickling ferrous metal comprising subjecting said metal to a dilute bath of sulfuric acid containing a small amount of a product obtained by sulfonating a mixture of an organic hydroxyl compound and a compound of the type formula in which R, R1, and R2 may be hydrogen, an alkyl group, an gr yl group or a substituted aryl group.

CHARLES H. MCCOLLAM. DWIGHT L. WARRICK. JOHN M. GOTSHALL.