VERFAHREN ZUM KATHODISCHEN AUFBRINGEN EINES CHROMHALTIGEN SCHUTZUEBERZUGS

摘要

A method of depositing a protective chromite conversion coating is described. The chromite coatings produced by the method contain no CrVI. The electrolyte used in the method comprises CrIII ions in a concentration of not more than 1 molar and a weak complexing agent for CrIII ions. The electrolyte, preferably, also contains conductivity salts. The method involves using a cathode current density of not more than 2000 amps per square meter and a temperature of not more than 35 DEG C. for a period of not more than 3 minutes. The chromite conversion coatings can be improved by aging and can be subsequently painted or lacquered. The CrIII electrolytes used are much less corrosive than CrVI electrolytes and thus the substrates which can be coated include materials which cannot readily be chromate coated because they are reactive towards CrVI electrolytes.