US1984534A

US1984534A - Method of cleaning nonferrous alloys

Info

Publication number: US1984534A
Application number: US649596A
Authority: US
Inventors: Leonard O Larsen
Original assignee: Western Electric Co Inc
Current assignee: AT&T Corp
Priority date: 1932-12-30
Filing date: 1932-12-30
Publication date: 1934-12-18
Anticipated expiration: 1951-12-18

Description

Fatented I Dec. 18,1934

UNITED STATES METHOD OF CLEANING NONFERRDUS ALLOYS Leonard 0. Larsen, Downers Grove, 11]., assignor to Western Electric Company, Incorporated,

New York, N. Y., a corporation of New York No Drawing. Application December 30, I932,

Serial No. 649,596

Claims.

This invention relates to a method of cleaning non-ferrous alloys, such as brass, bronze and similar alloys.

In the process of cleaning non-ferrous alloys by the acid dip method, it is customary to use sulfuric acid, nitric acid or a mixture of sulfuric and nitric acids. When parts dipped in such a bath are exposed to the atmosphere during the clipping process, they often become discolored or stained.

An object ofthe invention is to provide an expedient and eficient method of cleaning nonferrous alloy parts.

In accordance with one embodiment of the invention, brass or phosphor bronze parts are dipped in a bath comprising a mixture of sulfuric, nitric and phosphoric acid and upon removal from the bath the parts are rinsed in water, subjected to asodium cyanide bath to neutralize any remaining acid, and again rinsed in water and dried. This process leaves the parts bright and without stains.

A complete understanding of the invention will be obtained from the following detailed description.

When brass and phosphor bronze parts are acid dipped .manually, the parts are usually placed in a basket and immersed in a bath of sulfuric acid or a mixture .of sulfuric acid and nitric acid. The parts are then agitated inthe basket while they are immersed. During withdrawal of the basket from the bath agitation of the parts is avoided as much as possible so that they will be surrounded by acid fumes while exposed to the atmosphere in transferring the parts to a rinsing bath of water. In automatic machine dipping, the parts are in some instances agitated in the acid bath by dropping or pouring them into a basket immersed in the acid bath, and in this manner the entire agitation of the parts is provided for. When the basket is withdrawn from the acid bath, the parts are transferred to another basket immersed in a rinsing water bath by pouring the parts from the first basket into the second basket and consequently the parts are agitated while in the air whereby the acid fumes surrounding the parts are dispersed and the parts are exposed to the atmosphere causing discoloration and staining of the parts. This appears to be due to the fact that a dilute acid attacks the zinc in the brass or the tin in the bronze to a greater extent than the copper in these alloys, leaving copper stains on the surface of the parts. As long as the parts are in the bath, the spent (Cl. ES -8) acid in contact with the surface of the parts is replenished by more concentrated acid in the bath. However, it is believed that when the parts are removed from the bath, only a small amount of the-acid adheres to the parts and this quickly becomes diluted due to the formation of metallic sulphates and nitrates, and consequently stains are formed upon the parts.

It has been found that when an inhibiting agent, such as a phosphorus compound, preferably phosphoric acid, is added to the acid bath, the parts maybe exposed to the air after dipping in the acid bath without the appearance of stains or discoloration on the parts. This also makes the present process particularly applicable to cleaning parts which are to be electroplated since the parts may be attached to the electroplating racks and dipped into the cleaning bath. On account of the spacing of. the parts on the electroplating rack, they will necessarily be exposed to the atmosphere on removal from the bath. However, the addition of the inhibiting agent prevents the formation of stains on the parts when exposed to the air. While either sulfuric or nitric acid may be used, it is preferable to use a mixture of the sulfuric and nitric acids. These acids may be mixed in various proportions, and phosphoric acid added in accordance with the concentration of the bath. A suitable mixture has been found to consist of sulfuric acid, 36% nitric acid and 14% phosphoric acid.

The process is exothermic and the bath usually rises above room temperature. Ordinarily no temperature control of the bath is necessary.

As a specific example of carrying out the process of the invention, brass or bronze parts may be poured into a basket and immersed'in a mixture of sulfuric, nitric and phosphoric acids. The basket is then withdrawn from the bath and the parts are poured into a basket immersed in a water rinsing bath. From the rinsing bath the parts are removed in the basket and poured into a bath of sodium cyanide to neutralize any acid 45 that has not been removed in the rinsing bath. The parts are then removed from the cyanide. bathand again rinsed whereupon they may be dried by a heated current of air.

, While the invention has been described in con- 50 nection with brass and bronze articles, it will be evident that it is equally applicable to other non-ferrous alloys containing copper, zinc or tin. Although the invention is especially advantageous in connection with automatic dipping methods, it also has utility when manual dipping is employed.

What is claimed is:

1. A method of cleaning non-ferrous alloys containing copper and another constituent selected from the elements zinc and tin which comprises subjecting the alloy to the action of a bath containing sulfuric acid and phosphoric acid.

2. A method of cleaning a non-ferrous alloy containing zinc in substantial amounts which comprises subjecting the alloy to the action of a mixture of sulfuric acid, nitric acid, and phosphoric acid.

3. A method of cleaning a non-ferrous zinc alloy which comprises immersing the alloy in a bath containing sulfuric and phosphoric acid, removing the alloy therefrom and permitting it to drain while exposed to the atmosphere, and transferring the alloy to a rinsing bath.

4. A method of cleaning non-ferrous alloys containing copper and other constituents selected from the elements zinc and tin which comprises subjecting the alloy to the action of a bath containing nitric acid and phosphoric acid.

5. A method of cleaning or pickling alloy metal containing copper and a metal of the group of zinc or tin which comprises subjecting the same to an acid pickling or cleaning bath and inhibiting the chemical action of the acid on the metal by the addition of phosphoric acid without interfering with the cleaning or pickling action of the bath and thereby reducing the formation of copper stains on the parts by incorporating in the acid bath a substantial amount of an inhibiting acid.

LEONARD O. LARSEN.