Abstract
The sacrificial corrosion protection ability of Al, Al-Mg, and Al-Si thermal spray coatings and the corrosion resistance of the defect part of the coatings, which was covered by a rust layer formed during an outdoor exposure or an accelerated corrosion test were studied by electrochemical techniques. A high-purity Al (>99.98%, Hp-Al) , a normal-purity Al (>99.5%, Np-Al) and Al alloys with 5% of Mg (Al-5Mg) , 5% of Si (Al-5Si) or 12% of Si (Al-12Si) were used for the material of the thermal spray coatings. The corrosion resistance of the defect part of the coatings was evaluated using the electrochemical reaction resistance (ERR) measured by the EIS technique. The ERR for the defect part of the Al-5Mg coating was superior than that for the defect part of other coatings, when the specimens had been subjected to the accelerating corrosion test. However, for the specimen subjected to an outdoor exposure test, the ERR for the defect part of the Al-5Mg coating was roughly equal to other coatings. The sacrificial corrosion protection ability of the Hp-Al coating was superior than other coatings, however the ERR for the defect part of it was inferior to that for the Np-Al coating.
