| 摘要 |
A method of producing chromium conversion coatings is described. The coatings are novel in that they are chromite i.e. Cr2O3 coatings rather than the conventional chromate i.e. CrO3 coatings. The invention includes a novel electrolyte for depositing chromite layers. The electrolyte is an aqueous solution containing CrIIIions, a weak complexing agent for CrIIIions and a poison for the electrodeposition of chromium metal. The electrolyte preferably also contains conductivity salts and may include other additives such as fluoride ion and boric acid. Examples of poisons are CrVIions, peroxide, nitrate, polyamines, phosphates and formaldehyde. The chromite conversion coatings can be improved by aging and can be subsequently painted or lacquered. The electrolytes of the present invention 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. |
