Improvement of electrochemical corrosion characteristics of AZ61 magnesium alloy with unconventional fluoride conversion coatings

Fluoride conversion coating was applied on wrought AZ61 magnesium alloy by the immersion of alloy in Na [BF4] molten salt. Two different temperatures 430 degrees C and 450 degrees C, and different treatment times of 0.5; 2 and 8 h were used for the coating preparation. The surface morphology and the cross-sections of the coatings were investigated by scanning electron microscopy, focused ion beam cutting and energy-dispersive X-ray spectroscopy. The electrochemical corrosion characteristics of coated material varied with processing conditions. A significant improvement of electrochemical corrosion properties of the AZ61 magnesium alloy coated with fluoride conversion coatings was revealed by the potentiodynamic tests and electrochemical impedance spectroscopy.