Black Z is a powder for processing a uniform, glossy black inorganic oxide finish to zinc-plated surfaces and zinc based die casting. The coatings are excellent for use indoors and outdoor; however for outdoor use the surface should be protected with wax, oil or lacquer. Black Z coatings are also excellent based for painting or enameling for better adhesion. Black Z is a mildly alkaline powder which is dissolved easily in water to make a blackening solution.

ADVANTAGES

• 100% concentrated powder form.
• Contains no Chromium compound.
• Develops a uniform, black and gloss finish.
• Costs 50% less than liquid chromium compounds.
• Very simple operation and control.

OPERATING CONDITIONS

The pH of fresh solution should be around 8.5. If the pH drops to 8 or less, it should be raised by careful additions of ammonium hydroxide solution.

Electroplated zinc surfaces normally need no mechanical finishing; however, if the plated surface is brushed a uniform black finish can be obtained.

The usual preparation for zinc plated surfaces is to rinse thoroughly after plating, the rinse in a ½ percent sulfuric acid solution to neutralize any trace of alkali, rinse again and then transfer to the blacking solution.

Chromate dips are unsatisfactory before blackening because they leave a passive film. The zinc die cast parts are given a similar treatment as follows.

1. Mechanical finish.
2. Mild soak like cleaner booster SM-405 or a vapor degreaser.
3. 1-2 minute immersion in a hot soak cleaner.
4. Rinse.
5. Dip in ½ % sulfuric acid.
6. Rinse.
7. Blacken in Black Z.
8. Rinse with hot water and dry with air.

NOTE

• Hot water allowed to dry may leave some stains on the finish.
• A cause for formation of white stains could be improper rinsing. A dip in ½ % Sulfuric Acid solution will remove the above mentioned white stain without attacking the Black Z coating.

CONTROL BATH

The solution is usually controlled by pH. Adding frequent small amount of ammonia solution is very effective for keeping the pH at 9.00. If a large amount of ammonia is added which will reduce the blackening speed sharply, the solution should be heated to near boiling in order to evaporate the excess ammonia.
Additions of Black –Z powder are made on a daily or bi-weekly basis depending on the volume of the blackened parts and when the blackening rate falls 25% below the rate when a fresh solution was made.

EQUIPMENT

Rubber coated steel, plastic coated steel or stainless steel tanks are used. Lead, copper alloy tanks and steel tanks are not recommended. Heating can be done by stainless steam soils, gas burners, or electric immersion heaters.

STRIPPING THE BLACK COATINGS

Black –Z deposits can be stripped in a 15-20 % chromic acid solution and then dip the parts in 1% sulfuric acid solution to remove any passivity.

CAUTION

Black –Z is a mildly alkaline salt. Operators should wear gloves and eye glasses during operation. While handling the powder avoid inhalation of ammonia. In case of contact with skin, wash with plenty of water. In case of contact with eyes, wash with plenty of water and call a physician.

The information stated herein is based on information and tests we believe to be reliable. The accuracy or completeness thereof is not guaranteed. Since conditions of use are outside our control, user shall, before using, determine the suitability of the product for his intended use and user assumes all risk and liability in connection therewith.