The inhibiting effects of cerium diphenyl phosphate on the corrosion and stress corrosion of 7075 aluminium alloy

This paper demonstrates the effectiveness of the compound cerium diphenyl phosphate (Ce(dpp) 3) as a corrosion inhibitor. The results presented show that Ce(dpp) 3 is an excellent inhibitor of pitting corrosion of aluminium alloy AA7075-T651 in a very aggressive environment of continuously aerated 0.1M sodium chloride (NaCl) solution. Polarisation studies indicate that in this solution, Ce(dpp) 3 acts as a cathodic inhibitor by reducing the rate of the oxygen reduction reaction, which results in a decreased corrosion current density and a separation of the corrosion potential from the pitting potential. This inhibition is due to the formation of a complex surface film consisting of hydrolysed forms of Ce(dpp) 3, cerium oxide, aluminium oxide and phosphate. A mechanism by which this film is formed is discussed. The paper also presents stress corrosion cracking (SCC) results, which show that Ce(dpp) 3 can effectively delay the initiation of SCC and reduce the rate of cracking in NaCl solution.