EFFECT OF THIOUREA ON THE CORROSION BEHAVIOR OF FERROUS AND ALUMINUM ALLOY IN CHLORIDE CONTAINING ENVIRONMENTS.

Thiourea has been successfully applied to a marine cathodic protection system of steel which is galvanically coupled with an aluminium alloy sacrificial anode. The protective efficiency was markedly improved by thiourea in sea water and the consumption rate of aluminium alloy also decreased. Furthermore, it is significant that the protected area ratio can be increased three times. The effect of thiourea concentrations on the protective efficiency was also explored. The possible engineering advantages of this combination are discussed accordingly. However, the protective behaviour found in sea water was different from that in pure NaCl solution. Evidence is presented suggesting that thiourea can promote the formation of protective dense calcareous film containing calcium carbonate with aluminium oxyhydroxide.