Corrosion Protection of WE43 Magnesium Alloy by Fluoride Conversion Coating

Abstract

Magnesium alloys are utilized in automotive and aviation industry due to their low density and good mechanical properties. However most magnesium alloys lose mechanical properties at high temperature. Another weak point of magnesium is its high corrosion rate. Alloying by rare earth elements improves mechanical properties, corrosion resistance, and heat stability up to 300 °C by formation of intermetallic phases. Further improvement of corrosion properties can be achieved by coating. Fluoride conversion coating is ideal for magnesium alloy due to its low thickness, good adhesion and easy preparation. In this work, WE43 alloy prepared by extrusion is immersed in hydrofluoric acid to obtain fluoride coating. Extruded pure magnesium is immersed the same way as WE43 for comparison. Surface and cross section of prepared coating and corrosion properties of prepared materials are characterized. Fluoride conversion coating decreased corrosion rate by one order of magnitude for pure magnesium and by half in case of WE43 magnesium alloy.