GB2140038A

GB2140038A - Solution for chemical polishing of brasses

Info

Publication number: GB2140038A
Application number: GB08412496A
Authority: GB
Inventors: Edward Zacny
Original assignee: Akademia Gomiczo Hutnicza
Current assignee: Akademia Gomiczo Hutnicza
Priority date: 1983-05-19
Filing date: 1984-05-16
Publication date: 1984-11-21
Also published as: DE3418620A1; GB2140038B; PL137973B1; PL242049A1; DE3418620C2; GB8412496D0

Abstract

An aqueous solution containing by weight 45 to 64 percent sulphuric acid, 0.05 to 4.0 percent ammonium nitrate, 0.05 to 1.0 percent urea, and 0.02 to 0.3 percent ammonium chloride. The solution does not produce harmful nitric oxide gases when used to clean brass.

Description

SPECIFICATION Solution for chemical polishing of brasses This invention provides a solution suitable for chemical polishing of brasses, particularly those with a high content of copper e.g. 2 63% by weight.

The term "brass" means an alloy of copper and zinc but which may also contain small amounts of other metals. The solution most often used for chemical polishing of brasses is concentrated nitrous acid, or solutions of this acid with various inorganic acids, salts and metal oxides. However, the scope of the aforementioned solutions, in spite of their good polishing properties, is limited because strongly toxic nitric oxides are produced during the chemical treatment which harm the workers and pollute the atmosphere.

The Polish Patent Specification No. P233,649 describes a chemical composition for polishing copper alloys, particularly brasses, containing by weight 35 to 45 percent concentrated sulphuric acid, 1 5 to 40 percent concentrated nitrous acid, 10 to 30 percent ammonium nitrate, 0.05 to 5.0 percent cadmium chloride, 2 to 1 5 percent sodium, potassium or ammonium phosphate, and 1 to 30 percent water. This composition is applicable mainly to brasses with low copper content containing up to 63 percent of copper by weight. Chemical treatment of brasses with higher copper content gives poor surface polish.

The invention provides an aqueous solution containing by weight 45 to 65 percent sulphuric acid, 0.05 to 4.0 percent ammonium nitrate, 0.05 to 1.0 percent urea, and 0.02 to 0.3 percent ammonium chloride.

The advantage of the solution according to this invention consists in the elimination of nitric oxides during the polishing process, as well as the possibility of a less expensive waste neutralization method. This is due to the fact that the waste contains mainly copper and zinc sulfates. The solution according to the invention is mainly used for products coated with an oxide layer without other contaminations, such as fats and greases.

Example I The solution for chemical polishing contains 60percent of sulphuric acid 3percent of ammonium nitrate 0.8percent of urea 0.2percent of ammonium chloride, and 36 percent of water by weight.

Pressed and annealed brass articles containing 70 percent of copper by weight and coated with a thin layer of scale were polished in the above solution at a temperature of 398 K for 70 seconds. The surfaces polished showed no surface defects. No emission of toxic gases, such as nitric oxides, sulphur dioxide etc. was observed during polishing.

Similar results were obtained using the solutions of Examples II and Ill.

Example II The solution for chemical polishing contained: 49 percent of sulphuric acid 1 percent of ammonium nitrate 1 percent of urea 0.05percent of ammonium chloride, and 48.95 percent of water by weight.

Example 111 The solution for chemical polishing contained: 64percent of sulphuric acid 4percent of ammonium nitrate 0.08percent of urea 0.15percent of ammonium chloride, and 31 .77percent of water by weight.

1. An aqueous solution containing by weight 45 to 65 percent sulphuric acid, 0.05 to 4.0 percent ammonium nitrate, 0.05 to 1.0 percent urea, and 0.02 to 0.3 percent ammonium chloride.

2. A solution according to Claim 1 substantially as herein described in any of Examples I to Ill.

3. A method of polishing brass which comprises contacting the brass with a solution according to Claim 1 or 2.

4. A method according to Claim 3 wherein the brass contains at least 63% by weight copper.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION Solution for chemical polishing of brasses This invention provides a solution suitable for chemical polishing of brasses, particularly those with a high content of copper e.g. 2 63% by weight. The term "brass" means an alloy of copper and zinc but which may also contain small amounts of other metals. The solution most often used for chemical polishing of brasses is concentrated nitrous acid, or solutions of this acid with various inorganic acids, salts and metal oxides. However, the scope of the aforementioned solutions, in spite of their good polishing properties, is limited because strongly toxic nitric oxides are produced during the chemical treatment which harm the workers and pollute the atmosphere. The Polish Patent Specification No. P233,649 describes a chemical composition for polishing copper alloys, particularly brasses, containing by weight 35 to 45 percent concentrated sulphuric acid, 1 5 to 40 percent concentrated nitrous acid, 10 to 30 percent ammonium nitrate, 0.05 to 5.0 percent cadmium chloride, 2 to 1 5 percent sodium, potassium or ammonium phosphate, and 1 to 30 percent water. This composition is applicable mainly to brasses with low copper content containing up to 63 percent of copper by weight. Chemical treatment of brasses with higher copper content gives poor surface polish. The invention provides an aqueous solution containing by weight 45 to 65 percent sulphuric acid, 0.05 to 4.0 percent ammonium nitrate, 0.05 to 1.0 percent urea, and 0.02 to 0.3 percent ammonium chloride. The advantage of the solution according to this invention consists in the elimination of nitric oxides during the polishing process, as well as the possibility of a less expensive waste neutralization method. This is due to the fact that the waste contains mainly copper and zinc sulfates. The solution according to the invention is mainly used for products coated with an oxide layer without other contaminations, such as fats and greases. Example I The solution for chemical polishing contains 60percent of sulphuric acid 3percent of ammonium nitrate 0.8percent of urea 0.2percent of ammonium chloride, and 36 percent of water by weight. Pressed and annealed brass articles containing 70 percent of copper by weight and coated with a thin layer of scale were polished in the above solution at a temperature of 398 K for 70 seconds. The surfaces polished showed no surface defects. No emission of toxic gases, such as nitric oxides, sulphur dioxide etc. was observed during polishing. Similar results were obtained using the solutions of Examples II and Ill. Example II The solution for chemical polishing contained: 49 percent of sulphuric acid 1 percent of ammonium nitrate 1 percent of urea 0.05percent of ammonium chloride, and 48.95 percent of water by weight. Example 111 The solution for chemical polishing contained: 64percent of sulphuric acid 4percent of ammonium nitrate 0.08percent of urea 0.15percent of ammonium chloride, and 31 .77percent of water by weight. CLAIMS