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Practical Plating-Filtration Tips You can spend a million dollars on an automated plating system and still produce poor quality if your filtration equipment is not adequate to keep your plating solution free of particulate matter.

Proper filtration is the single most important thing you can do to improve the quality of deposits from any plating bath. The following instructions will help you in maintaining a virtually reject-free, high-production plating solution.

  1. When using a filter that requires a pre-coat, determine the area of the filter surface to be pre-coated. Use two to two and one half ounces of diatomaceous earth or one ounce of cellulose pulp per sq. ft. of filter surface. Mix one half of the required amount in the slurry tank, circulate until deposited on the filter plates, then add the remainder of pre-coat to the slurry tank and circulate again. You will obtain a perfect pre-coat.

  2. If using powdered carbon, mix equal amounts of carbon and diatomaceous earth by weight, then circulate the solution through it.

  3. Determine the absolute pressure produced by the filter's pump by closing the discharge valve between the filter and the tank. This shows you the ultimate pressure that can be produced by the pump. Once you know this, watch the pressure gage as filtration of your plating solution proceeds, When three-fourths of the ultimate pressure has been reached, clean the filter. If you do not, the dirt load in your tank is getting ahead of your filter, instead of the other way around. Let this continue and in a very short time you will be having problems with roughness.

  4. The pH of a bright nickel bath should be kept as close as possible to that which has been found to produce the brightest plate. THIS IS VERY IMPORTANT! Bright and semi-bright baths generally operate in a pH range of 3.5-4.2. When the pH rises to a point over 4.2, precipitation of iron is more likely to occur, and this will plug a filter very rapidly.

    Iron contamination and plugging of the filter are also more likely if iron and steel parts that fall from the rack are allowed to remain in the tank. Such parts will create a lot of free iron in the bath. Dropped parts should be removed from the bottom of the tank every night.

  5. It has been discovered within the last few years that one turnover an hour is not enough to keep the bath as free of roughness-causing particles as it should be. Therefore two to two and one half times per hour is recommended. This has been proven.

    Not to be forgotten is the important part the anode bag plays in your plating operation. We have found that a napped polypropylene anode bag, of 13 ounce material, and pumping rater of 7 to 13 gpm, produce best results. A rubber-bottom bag will help to eliminate the fines that can escape into the bath.

Anode bags in a high-production operation should be replaced every six months for best efficiency.

By following the preceding instructions and by keeping your bath in proper balance, you should produce finishes as close to plating perfection as possible!

Reprinted by Permission of Products Finishing, 6600 Clough Pike, Cincinnati, Ohio 45244

Anode Product's Slim-Line Filtration Systems...A Practical Answer

Handy Guide for Selection of the Right Fabric Bag

12 oz. Cotton Duck: Can be used in nickel baths. Least porous of our fabrics. Excellent material for double bagging.

7.5 oz. Cotton Sateen: Desized material, bleached and washed. Recommended for cyanide copper.

210 Denier Nylon: This fabric is not used as much as in the past, but it is still a viable alternative with less corrosive baths. Good for aklaline Solutions.

9 oz. Polypropylene: Popular bag for many solutions. Also used for outer bag when double bagging. Good for tin, sulfate and acid zinc, and sulfuric acid. Corrosion resistant.

13 Oz. Polynap: Heavier weight fabric, sateen weave, napped on one side. Should make double bagging unnecessary. Highly recommended for nickel and acid copper baths. Holds fines better.

Fiber Max.
Cu. Ft.
General Resistance to Chemicals
Alkalies Mineral
Cotton 180°F 3-4 Good Poor Poor Fair Very Good
Nylon 200°F 15-20 Good Poor Poor Fair Very Good
200°F 30-50 Excellent Excellent Excellent Good Excellent
Polynap 200°F 30-50 Excellent Excellent Excellent Good Excellent

Note: CFM's are based on the Frazier method of testing.
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