BRIGHT ZINC ELECTRODEPOSITION FROM AN ACID ELECTROLYTE

Zinc electroplating baths are mostly of the alkaline-cyanide type, of high toxicity. A new acid bright zinc electrolyte is presented. Five organic substances have been tested as brighteners. The optimum bath composition and operating conditions for obtaining satisfactory bright deposits of zinc are indicated. The throwing power of the bath, measured using a Haring-Blum cell, was very high (15 %); the current efficiency was also high (97 %), as well as the deposition speed: 1,1-mu-m.min-1 at 0,035 A.cm-2. The zinc electrodeposits have very good adhesion to the base metal, are free of porosity, and have a fine grain size and good brithtness as observed in the microscope.