Brass Maintenance

Univertical’s Brass Maintenance solution is an easy to use concentrate formulated for the make up and maintenance of conventional brass plating solutions. It is manufactured using anode grade metals and high quality cyanides under an ISO 9000:2000 approved quality system to insure the highest quality product.

Typical Analysis:

Copper Metal 11 oz/gal
Zinc Metal 2.75 oz/gal
"Total” cyanide 11 oz/gal

Bath make up:

• High Speed Plating

1. Dilute 2 parts concentrate with one part of water.
2. Adjust pH between 10.0 to 11.0
3. Maintain temperature at 160 ° F

• Barrel Plating

1. Dilute one part of concentrate with two parts of water.
2. Adjust the pH between 10.0 and 10.5
3. Maintain the temperature at 140 ° F

• Still Plating:

1. Dilute one part of concentrate with four parts of water.
2. Adjust the pH between 10.0 and 10.5
3. Maintain the temperature at 100 ° F

Raise the pH with caustic soda and lower the pH with bicarbonate of soda. DANGER! Too low a pH can cause evolution of lethal Hydrogen cyanide gas! Additions should be small and slow to minimize the possibility of over adding bicarbonate of soda.

Role of ingredients:

The most important factor in controlling the ratio of copper and Zinc in the alloy is the “total” cyanide to Zinc ratio. To plate a ration of 70/30 copper to Zinc, the “total” cyanide to Zinc ratio should be about 4 to 1; Highest ratios can raise the copper up to 90% in the plate; lower ratios will increase the Zinc content but are not recommended since the Zinc Cyanide Solubility is limited under the specified ratio.

Additions of ammonia up to 1% by volume will increase the Zinc content of the deposit and brighten the plate.

An increase in temperature will increase the efficiency. Operation temperature should be at least 80 ° F with higher temperatures required for fast plating. Too high temperatures will lower the ammonia content of the bath.

Carbonates are desirable because they buffer the pH, but high concentrations will reduce the efficiency of the bath while lowering the conductivity; very high concentrations will reach saturation level and precipitate thus physically rendering the bath inoperable; and 3 oz/gal. of Sodium Carbonate concentration is recommended.

ANALYTICAL PROCEDURES:

Copper:

• Pipette 1 ml of sample into a 500 ml Erlenmeyer.
• Add 5mls of concentrated Nitric Acid, Caution! Under the hood.
• Warm up until boiling. Let cool down.
• Add drop wise, concentrated ammonium hydroxide until blue precipitate formed, darkens.
• Add Acetic Acid drop wise until precipitate clears, add 2 mls extra,
• Add 20 mls of water and 10 grs of Potassium Iodide. Shake until the precipitate redissolves; if it does not redissolve completely, add more Potassium Iodide. Add 5 mls of starch solution.
• Titrate with .025 N Sodium thiosulfate solution until colorless.

Ounces/gal Copper = .212 x mls of thiosulfate

Zinc:

• Pipette 5 mls of sample into 500 Erlenmeyer.
• Add 10 mls of concentrated Nitric Acid. Caution! Under the hood.
• Warm up until boiling. Let cool down.
• Add concentrated ammonia slowly until the precipitate formed, redissolves. Cool down.
• Add 50 mls of water and enough eriochrome black T to get a nice wine color.
• Add 5 mls of Formaldehyde solution and immediately titrate with .IMEDTA until color changes to blue.

Ounces/gal Zinc = .17 x mls of EDTA

“Total” Cyanide:

• Pipette 1 ml of sample into a 500 mls Erlenmeyer.
• Add 5 gms of caustic soda.
• Add 50 mls of water. Shake until the caustic is completely dissolved.
• Add a few crystals of Potassium Iodide and titrate with silver nitrate .IN until faintly turbid.

Ounces/gal “total cyanide = 1.31 of Silver Nitrate .IN