Evaluation of corrosion performance of surface treatments on aeronautical magnesium alloys by the impedance technique

摘要

Magnesium alloys are increasingly used in aeronautical secondary structural parts for their low density and good mechanical properties. The auto-ignition and flammability issues associated with the first generations of alloys are now solved but the main drawback of magnesium alloys is their limited corrosion resistance. Corrosion mechanisms of magnesium alloys are still in discussion, particularly the origin of the unusual anodic hydrogen evolution commonly called "negative difference effect" (NDE). Moreover, chromates replacement in surface treatments leads to the necessity to develop chrome-free protective treatments for magnesium alloys parts. Chemical conversion treatments are of low-cost and could be considered as effective to prevent corrosion and promote the adhesion of primer coating in typical structural applications.