US2043300A - Cleaning process - Google Patents

Description

' Patented June 9, 1936 PATENT OFFICE CLEANING PROCESS Paul McDorman, Dayton, Ohio, assignor, by

mesne assignments, to General Motors Corporation, a corporation of Delaware 1 No Drawing. Application January 27, 1932,

' Serial No. 589,321

10 Claims. (01. 1488) This invention relates to a process for cleaning metals. It is intended to be used for the cleaning of new metals, especially sheet steel for electro plating, dip plating, galvanizing, paint- 5 ing, vitreous and non-vitreous enameling, for the cleaning of de-enameled sheets of metal, or for any other purpose in which steel may require a clean surface.

Inthe manufacture of articles made of drawn metal, it is necessary to use a lubricant known as the drawing compound. This compound must be removed from the drawn metal, otherwise the enamel, paint, plate or other finishing material usually applied to the article, will pull or break, thus causing a bare spot on the metal.

Heretofore it has been the custom to use as lubricants during the drawing operation, drawing compounds made of soap, vegetable or other water soluble oils, because such compounds are the only compounds that could be successfully cleaned from the metal after it had been fabricated. Such drawing compounds do not have good lubricating properties and for this reason the losses during the drawing operation, from tom metal, especially from deep drawn articles, have been prohibitive andhave made the use of expensive specially made deep drawing metals necessary for this type of work. I

My invention, which will be hereinafter specifically described, permits the use of hydrocarbon, mineral or petroleum oils, or compounds containing these materials as drawing compounds or lubricants. The use of this type of drawing compound, due to betterv lubricating properties, results in smaller drawing losses, larger variety of articles made, faster operation of the process, less scarring of the metals, lower cost of the drawing compounds,'and, above all, will permit the use of much cheaper metals. It will also- 40 permit the oiling of the metal at the rolling mills to prevent subsequent rusting, :a very important item where metal is to be maintained in storage for any length of time.

' Myv cleaning process consists essentially in treating the metal to be cleaned with moist chlorine gas. Specifically, my process is carried out by passing the metal to be cleanedinto' an atmosphere of moist chlorine gas by allowing it to dip through a water seal, the water seal being maintained preferably at approximately 120 F.

The metal is maintained in the chlorine atmosphere for approximately three minutes, is then dipped or rinsed in water, and then returned to the chlorineatmosphere for another three min- 65 utes. The metal isthen again dipped or rinsed by passing through a water seal of substantially clearrunning water, and finally passed into a neutralizing solution.

The neutralizing solution may be any alkaline solution, such as soda ash, borax, silicates or com- 5 binations thereof. i

It is important in the above described process, that the chlorine atmosphere be maintained moist and that the metal treated should not be allowed to become dry either at the beginning of the op- 10 eration or while in the chlorine atmosphere. otherwise the products of chlorinization become insoluble in water and can only be removed by means of acids. Also, chlorine gas acts very slowly or not at all on dry metal. 15

Preferably, as indicated above, the metal being treated should be intermittently treated with Y Water to remove theproducts of chlorinization.

If this rinse is omitted, protective coatings may be formed on the metal which will greatly re- 20 tard the actionof the chlorine gas. The wetting therefore has a two-fold function, and preferably the metal should be wetted at least three times as set forth above.

I have found it advantageous to maintain the 25 flow of Water through the water baths as rapid as possible at all times and to maintain the water baths slightly acid in character. Acid baths prevent the formation of hydroxides of iron which are insoluble in both alkaline or neutral solutions. 30

By the foregoing outlined cleaning process, mineral, hydrocarbon, or petroleum oil may be 'used as the drawing compounds, for such compounds may be easily removed by my cleaning process after the articles have been fabricated. 35

ferro antimoniate. This clings tenaciously to 40 the metal and cannot be removed in the ordinary cleaning by acids or by mechanical means, and if not'removed will cause copper-heading and blistering of theground coat to follow. It is insoluble in water and all acids except nitric. 45 When the piece is subjected to an acid bath, other than nitric, the hydrogen formed by the action of the acid on the metal reduces the sodium ferro antimoniate to antimony anhydride. This compound, although it is insoluble in water and 50 acids and adheres to the metal, can be more or less successfully removed by vigorous hand scrubbing. By my process, treatmentin the chlorine bath will successfully remove the black smudge without the necessity of hand scrubbing.

My process may be carried out in any type of apparatus, but it is essential to use an apparatus that is made of material that will not react with wet chlorine and that will prevent the escape of chlorine gas into the atmosphere and that will permit the intermittent subjection of the metal to be treated first to the action of water, then to the action of chlorine gas, etc.

While specific time intervals and temperatures have been indicated throughout the specification, it should be understood that these time intervals and temperatures may be varied to suit the necessity of the particular class of work being done. For example, in some cases, a slightly longer period of time in the chlorine atmosphere may be necessary.

What is claimed is as follows:

1. The method of cleaning metal comprising passing the metal through an atmosphere of moist chlorine gas at a temperature below the dissociation temperature of HCl. I

2. The method of cleaning metal comprising passing the metal through an atmosphere of moist chlorine gas at a temperature below the dissociation temperature of HCl and neutralizing the treated metal.

3. The process of cleaning metal which comprises wetting the metal with water, reacting the moist metal with moist chlorine gas in an atmosphere of moist chlorine gas.

4. The process of cleaning metal which comprises wetting the metal with water, reacting the moist metal with moist chlorine gas in an atmosphere of moist chlorine gas'and neutralizing the treated metal.

5. The process of cleaning metal comprising passing the metal to be treated through a water metal with moist chlorine gas, in an atmosphere of moist chlorine gas again wetting the, metal, and again interacting the metal with moist chlorine gas.

8. The process of cleaning metal comprising wetting the metal with water, interacting the metal with moist chlorine gas, again wetting the metal, again interacting the metal with moist chlorine gas in an atmosphere of moist chlorine gas, and finally neutralizing the treated metal.

9.-The process of cleaning metal which com prises interacting the metal with chlorine gas in an atmosphere of moist chlorine gas while maintaining the metal moist and while excluding the air from contact with the metal.

10. The process of cleaning metal which comprises passing the metal to be treated through a water seal into a chamber containing moist chlorine gas, removing the treated metal from the chamber through a water seal and maintaining the water seal at approximately F.

PAUL MGDORMAN.