Dichromate and chromate salts are oxidizing agents. Hexavalent chromium is used in chrome plating, chromate coatings and primers, and in chromic acid. In aqueous solution, chromate and dichromate anions exist in a chemical equilibrium. Both methods use acidic chromate or dichromate solutions. The chromate and dichromate ions are fairly strong oxidizing agents. In an aqueous solution, chromate and dichromate ions can be interconvertible. The chromate is converted by sulfuric acid into the dichromate. Oxidation can also be effected using conventional stoichiometric chromate or permanganate reagents. Anodizing can be performed in combination with chromate conversion coating. Exposure to zinc chromate can cause tissue ulceration and cancer. This is isoelectronic with permanganate and chromate ions. The hydrated chlorides are prepared by treatment of chromate with hydrochloric acid and methanol. Oxidation with chromate affords perinaphthenone and then naphthalene-1,4,5,8-tetracarboxylic acid. This yellow solid is the potassium salt of the chromate anion. Potassium peroxochromate (K[Cr(O)]) is made by reacting potassium chromate with hydrogen peroxide at low temperatures.