Corrosion characteristics of cold gas spray coatings of reinforced aluminum deposited onto carbon steel

Abstract

The morphology, chemical, mechanical and corrosion characterization of starting materials, and Al and Al-Al 2 O 3 /Al coatings obtained by Cold Gas Spray and applied on common steel substrate were performed. An Al coating on a ground or grit blasted substrate, and Al-Al 2 O 3 /Al coating on ground mild carbon steel have been compared. The electrochemical results showed that the coatings protect the substrate for immersion times >2000 h due to the dense structure obtained by Al and Al-Al 2 O 3 . The electrolyte reaches the substrate only after 2000 h of immersion without wetting completely the coating/substrate interface. Coatings have resisted 3000 h of salt fog test.

Cold gas spray coatings: basic principles corrosion protection and applications

“…This happens because the particles deform more severely on a rough surface than on a smooth surface. In addition, these coatings show greater adhesion on blasted substrates 3,22,47,48 .…”

“…This is a great advantage as it prevents exposure of the clean surface to the environment for a long time, preventing the formation of oxides or deposition of dirt on the surface. Studies report that when CGS coatings are deposited on rougher surfaces, the deposition efficiency of the material increases 3, 31,47,48 . This happens because the particles deform more severely on a rough surface than on a smooth surface.…”

“…The corrosion resistance of CGS coatings depends mainly on the porosity and thickness of the coatings. Coatings with corrosion resistance for long immersion times show porosity values less than 1% and can be considered as compact 35,47 . They also show an increase in the corrosion resistance by increasing their thickness.…”

“…Even utilizing spray techniques such as HVOF and Plasma Spray, the deposition of aluminum coatings was difficult because of the high temperatures used during the spray process that causes the melting of the feedstock material and a high oxidation of aluminum. An extensive literature 52,53, shows the production of the aluminum CGS coatings and in some of these works 47 47 . The Al/grit blasted steel show a thickness of 381µm, which was thicker than the Al/ground steel (309 µm) and the reinforced coating (320 µm).…”

“…It is mandatory that the substrate be clean and free from chemical residues and oxides prior to coating deposition. Before spraying, the preparation of the substrate is mainly done in two ways: abrading using silicon carbide papers (SiC) which provides a roughness around 0.5 μm, or blasting, which is the most widely used method, in which Al 2 O 3 particles are blasted on the substrate surface, what may produce a surface roughness up to 5 μm 47 . To prepare the surface by blasting procedure, it is important to define the following parameters / conditions: the type of particle used, its size and shape, gas pressure, angle, and time of blasting, as these characteristics can determine how rough the surface may be 31,48 .…”