US1886411A - Art of removing lead from ferrous articles - Google Patents

Description

. as above Patented Nov.

UNITED STATES OHARLIN L. MANTELL, OF BROOKLYN NEW YORK, ASSIGNOR T0 DUDZEELE CORPORA- TION OF AMERICA, OF NEW YORK, N. Y., A CORPORATION OF DELAWARE ART OF BEHOVING LEAD FROM FERBOUS ARTICLES 80 Drawing. Application filed March 29, 1929, Serial No. 351,131.

My invention relates to the art of removing coatings of lead or lead alloys from tubes or other ferrous articles, such as tere plate, scrap, rods, wire, etc.

Broadly, the invention consists in removing the lead coating by subjecting the art cle (as by immersion) to a solution contain ng appreciable amounts of chlorides and hydrogen ions resulting from the use of a nonoxidizing mineral acid with a small amount of a catalytic material such as nickel, salts; for example, chloride or sulphate of mckel.

Lead is one of the best known metals entployed as a material of construction for corrosion resistance. Its use in the manufacture of sulphuric acid and in the chemical mdustries is well known. It is quite resistant to many forms of chemical attack. The invention aims to remove lead or lead alloys from articles by subjecting them to a solution which attacks and removes or enables the removal of the lead without considerable or objectionable attack upon the ferrous article. The employment of a catalyst such referred to materially expedites or speeds up the reaction upon the lead coating and thus by reducing the time of sub ect1on of the article to the deleading bath, reduces the corrosion effect upon the main body of the article.

In carrying out the process in one approved way, the tubes or other articles to be deleaded are first cleaned in an alkaline solution, such as sodium hydroxide, at a temperature preferably near the boiling point; or heated aqueous solutions of so-called commercial cleaners may be employed, or alkali solutions with emulsifying agents such as sulphonated 011s, and various detergents (as sodium carbonate, phos hates, etc.) e

Af fier cleaning, the 2111710168 are immersed in the deleading solution in the same general manner or method which is employed in pickling rolled or drawn steel articles.

A preferred deleading solution, as generally described, comprises appreciable amounts of chlorides and hydrogen ions resulting from the use of a non-oxidizing mineral acid.

with a small amount of a catalyst, such as nickel salts,

or equivalent.

Renewed March 14, 1932.

As a specific example of one approved solution, t 0 following ingredients and proportions are stated:

Sodium chloride (common salt) in concen trations from about 15% of weight up to saturation, acidified by approximately 5% sulphuric acid, and as a catalyst, a nickel salt, such as chloride or sulphate or nickel, in concentrations from as low as one one-thousandth stituted for the sulphuric acid, the sulphuric being preferred in commercial work because it is a cheaper reagent.

In plant operation it is desired that the solution shall Work upon and remove the lead without marked effect on the ferrous metal or alloy composing the main bulk of the fabricated article. The addition of nickel salts to the bath has been found markedly to speed up the reaction, and thus to reduce attack up on the ferrous body. The bath is desirably maintained at a temperature from 180 F. up to the boiling point of the solution.

After removal from the deleading bath the articles are washed, preferably in hot water, to dissolve and wash off any lead chloride or lead salts still adhering.

The time-required for deleading is a function of the size of the article, the thickness of the coating, and the surface finish desired.

Soluble platinum salts may be used in low concentrations in place of nickel salts, but are usually unavailable for this purpose because of the higher cost. Accordingly, wherever I refer in the claims the catalyst, I mean any material which is substantially the equivalent of nickel salts in the sense that it will bring about to a practical-extent the results herein attributed to the presence of nickel salts. It is believed to nickel salts as ing appreciable amounts that the catalytic action of the nickel salt is as follows The nickel ions are precipitated as nickel atoms on the surface of the lead to form a nickel lead electrolytic couple, as the result of which the attack on the lead and its resultant solution is accelerated.

The present invention is an improvement upon that disclosed in my prior application, Serial No. 325,643, filed December 12, 1928, and consists largely in the addition to certain typical deleading solutions therein disclosed, of a catalyst of the character and for the purposes above described.

I claim:

1. A deleading solution containing appreciable amounts of chlorides and hydrogen ions resulting from the use of a non-oxidizing mineral acid, with a small proportion of a nickel salt as a catalyst.

2. A deleading solution containing sodium chloride in concentrations from approxmate- 1y 15% by weight up to saturation, and approximately 5% non-oxidizing mineral acid, and a nickel salt as a catalyst in concentrations from approximately 1000th of 1% to approximately of 1%.

3. A deleading solution containing sodium chloride concentrations from approximately 15 by weight up to saturation, and approximately 5% as a catalyst in concentrations from approxirpagly 1000th of 1% to approximately 0 1 o.

4. A deleading solution containing sodium chloride in concentrations from approximately 15% by weight up to saturation, and approximately 5 non-oxidizing mineral acid, and a nickel salt in small percentage as a catalyst.

5. A deleading solution containing sodium chloride concentrations from approximately 15% by weight up to saturation, and approximately 5% sulphuric acid, and a nickel salt in relatively low concentration as a catalyst.

6. A deleading process including, as a characteristic operation, subjecting a leadcoated ferrous article to a solution comprising appreciable amounts of chlorides and hydrogen ions resulting from the use of a non-oxidizing mineral acid, with a small proportion of a nickel salt as a catalyst.

7 A deleading process including as a. characteristic operation subjecting a lead coated ferrous article to a solution compris ing sodium chloride in concentrations from approximately 15% by weight up to saturation, and approximately 5% non-oxidlzing mineral acid, and a nickel salt as a catalyst in concentrations from approximately 1000th of 1% to approximately of 1%.

8. A deleading process including, as a characteristic operation, subjecting a leadcoated ferrous article to asolution comprissulphuric acid, and a nickel salt of chlorides and hydrogen ions resulting from the use of a non-oxidizing mineral acid, with a small roportion of a nickel salt as a catalyst, the ath being maintained at a temperature near boilmg.

9. A deleading process including, as a characteristic operation, subjecting a leadcoated ferrous article to a solution comprising appreciable amounts of chlorides and hydrogen ions resulting from the use of a non-oxidizing mineral acid, with a small proportion of a nickel salt as a catalyst, the bath being maintained at a temperature from approximately 180 F. to boiling.

10. A deleading process including as a characteristic operation subjecting a lead coated ferrous article to a solution comprising appreciable amounts of chlorides and hydrogen ions resulting from the use of a non-oxidizing mineral acid, with a small proportion of a nickel salt as a catalyst, the bath being maintained at a temperature near boilin 11. The described process, including as characteristic features, cleaning lead-coated ferrous articles in an alkaline solution, subjecting them to a deleading bath of character described in claim 1, and washing the articles to remove remaining lead and deleading solution.

12. The described process including as characteristic features, cleaning lead-coated ferrous articles in an alkaline solution, subjectin them to a deleading bath of character descri ed in claim 2, and washing the articles to remove remaining lead and deleading solution.

13. A deleading solution containing appreciable amounts of chlorides and hydrogen ions, with nickel salt as a catalyst.

In testimony whereof I aflix my s 'i%ature.

CHARLES L. MAN LL.