Studies of the conversion coatings formed by combined use of lanthanum salt and benzotriazote on commercial brass

摘要

Conversion coatings on commercial brass were prepared with lanthanum salt (La(NO_3)_3) and benzotriazole (BTAH) as reagents. A "Critical La(NO_3)_3 content" and "Critical BTAH content" were both observed, at which the coatings prepared performs the highest protectiveness.The results showed that La(NO_3)_3 and BTAH had an excellent synergism effect on the corrosion inhibition of brass. A remarkable enhancement of the brass's corrosion protection was obtained by the formation of conversion coatings consisted of Cu_2O, La_2O_3, Cu(I)BTA and La-complex, which acted as a barrier avoiding the release of metal ions and inhibited the diffusion of the oxygen.