Anodes and zinc plating baths

The article includes a number of practical advices on the operation of anodes based on the author's great experience in the sphere.
Both plate and bulk anodes are considered in alkaline and acid solutions. Rolled or cast anodes are suitable for small-scale production. The hook should be made of titanium for acid solutions and of ordinary steel for alkaline ones. True anode surface area is gradually degreasing in case of implementing plate anodes (Fig. 1) which causes uneven application of coating layer especially in acid baths. The best way to solve anodes problems is to use bulk anodes. Anode baskets are made of steel for alkaline solutions and they work to some extent as insoluble anodes, thus reducing zinc built-up in the bath. Zinc concentration in the plating solution is normally determined once per day and in case of increasing concentration up to 30% anode baskets should be replaced by steel plate anodes. This prevents further increase in the concentration and allows to stabilize it. 30 year experience of ball anodes operation at Lada car plant has proved effectiveness of this technology. Zinc oxide has never been used for replenishment. In acid baths titanium baskets are used. They are placed into polypropylene bags in order to catch anode slurry.