The corrosion resistance of a thermally sprayed coating was evaluated by the combined cycle corrosion test (CCT) ; the coating was formed on a steel substrate by a flame spraying with the Al-5Mg-0.15Ca alloy comprising 5 mass% of Mg, 0.15mass% of Ca and the balance Al. Two types of samples that was different in the thickness of the coating, 50 μm and 100 μm were prepared. The samples were subjected to the CCT after giving a cross-cut to the steel substrate on the coating. After finishing the certain period of the CCT, the cross-sectional distribution of elements and phases across the coating of the tested samples was examined by SEM-EDX and EBSD analysis.
Red rust-spots appeared on the samples after subjecting them to the CCT for 6000 h, regardless of the level of the coating thickness; they developed on a white-rust layer formed on the coating nearby where the cross-cut had been given. The SEMEDX analysis showed that the part of the white-rust layer was covered with the thin layer of a corrosion product, which was estimated as calcium carbonate.
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