Comparative evaluation of the marine corrosion resistance of aluminum coatings deposited by thermal spray FS, ASP and HVOF

The results of the salt spray corrosion assay of test specimens prepared with the oxyacetylene flame of thermal spray process, electric arc and HVOF, without sealing, are presented in this work. The test specimen were exposed up to 25.000 hours in a sodium chloride solution meanwhile the steel exposition assay rise up to 10,000. The results consider the evaluation of the aluminium oxide layer behavior and its participation as protective element of the steel substratum, besides registering through the metalografic examination how the layer is affected by the test saline enviroment. It can be concluded that in the salt spray corrosion assay, the superficial corrosion products (hidrated aluminum oxide and/or aluminum hydroxide) can be adherent and act as additional protection barrier. Still, its propagation for the interior of the covering depends on the adherence and cohesion of the deposited layer. Better results had been seen when the layers had been deposited by the flame process, with a 120 ºC preheated substratum.