The surfaces of the corroded coatings that underwent salt spray and atmospheric corrosion are shown in Fig.1.According to the x-ray defraction(XRD) detection result of the corroded coating surface(Fig.2) and the neutral saltspray corrosion research results on the aluminium alloy, colloidal Al(OH)3/Al0(OH) and oxide of aluminium covered the coating surface after 96 h of salt spraying. White particles on the coating surface suffered atmospheric corrosion probably due to the air-seasoning of the colloidal Al(OH)3.
Fig.1 Surface morphologies of the corroded coatings resulting from (a) salt spray (96 h) and (b) atmospheric corrosion (1046 h)
Fig.2 XRD detection results of the as-sprayed coating (a) and corroded coating (b)
SEM observation and energy-dispersive x-ray spectroscopy(EDS) analysis were conducted on the corroded coating surface(the corroded coating samples were ground with sand paper and polished). As presented in Fig.3, the metal phase in the coating experienced corrosion and resulted in some large and deep pores. As a result of the corrosion, gaps between the metal and lubrication phases appeared. The EDS results indicated that the corroded coating metal phase was mainly composed of aluminium and oxygen. In the other area, elements, such as Na, Cl and Si, were identified, indicating that many corrosion products were produced.
Fig.3 (a,b) SEM morphologies of the corroded Al/BN coating surfaces and EDS results in the (c)(d) metal and (e,f) nonmetallic phases
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