ESA STM-276 Assessment of Chemical Conversion Coatings for the Protection of Aluminum Alloys

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In this study, the aluminium alloys A17075, Al22l9 and Al5083 were used as substrates for evaluation of the chemical conversion coatings. Among various chemical conversion coating systems, three alternative conversion coating pretreatments were selected for evaluation: Alodine 5700, Nabutan STI/310 and Iridite NCP. The chromium (VI) conversion coating Alodine 1200 was used as the reference. The quality assessment of conversion coatings was evaluated by optical and scanning electron microscopy. Coated samples were characterised by salt spray exposure in order to simulate ground storage conditions; thermal cycling under vacuum, which simulates an in-orbit space environment; and electrical resistivity, as spacecraft sub-systems are electrically grounded to one another