Studies of anodic polarization in 0.5mol/l H

2

SO

4

were made to examine the corrosion behaviour and microhardness of surface alloys formed by implanting N

B

Cr and Mo ions into pure iron specimens. No notable change of corrosion potential was observed. The critical and passive current densities

however

were decreased markedly. It was found that the range of passivity was increased and the microhardness improved. Results suggested

also

that multi-element ion implantation was better than single-element ion implantation.