Conversion coatings on magnesium alloys' surface

abstract

English

Magnesium alloys are one of the important structural materials. Problem is that corrosion rate of these materials is really high. Conversion coatings are of themost effective protection against corrosion. Surface of of the magnesium alloys AZ31, AZ61 and AZ91 was treated by phosphate-permanganate and chromate conversion coatings. Chromate is one of the suitable way of conversion coating, but it cannot be used of carcinogenic Cr(VI). In our case, chromate conversion coating was taken as standard. Magnesium alloy AZ91 contains approximately 9 % of alluminium, which causes formation of phase Mg17Al12. This phase is larger in AZ91 than in AZ31 and AZ61. Phase Mg17Al12 has the highest electrochemical potential, so it behaves like cathode in magnesium alloy. It seems that the higher contens of phase Mg17Al12 cause the bigger micro-cells and the electrochemical corrosion is more significant.

Conversion coating, magnesium alloy.

TKACZ, J.; ZMRZLÝ, M.

16. 9. 2011

0009-2770

Chemické listy

105

Czech Republic

s946

s947

2