METHOD FOR PREVENTING CORROSION OF FORGED ALUMINUM ALLOY PRODUCT DURING HEAT TREATMENT

摘要

PURPOSE:To prevent the local corrosion of a forged Al alloy such as the pitting corrosion during heat treatment by using an aqueous nitrate soln. having a prescribed concn. as a quenching medium. CONSTITUTION:A forged Al alloy is heat treated by soln. heat treatment, hardening and aging. When the Al alloy is hardened, an aqueous soln. prepd. by adding =200ppm (expressed in terms of nitrate ions) nitrate to warm water is used as a quenching medium. The alloy is then aged without removing the aqueous soln. sticking to the surface. The nitrate ions in the aqueous soln. is converted into nitrite ions which act as a passivating agent.