A copper electroplating method revealed that recently developed commercial Al2O3 thermal spray coatings did not have the well-known lamellar structure but instead had a structure that was made up of tightly bonded particles, with many vertical microcracks in the coating. The coating in the study was prepared by the atmospheric plasma spray system. The copper electroplating method was applied to observation of the Al2O3 thermal spray coating structure. Spray coating specimens were electroplated in an aqueous solution containing CuSO4, H2SO4, CuCl2, and additives so that copper was deposited in small pores and narrow cracks in the coatings. Copper in the Al2O3 coatings was observed clearly by scanning electron microscopy, which also revealed the coating’s structure (boundaries of flattened particles and vertical cracks). The coating did not have a lamellar structure (horizontal apertures between flattened particles) and it was dense in spite of the many microcracks.

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