Corrosion protection of AA6061 T6-10 % Al2O3 composite by molybdate conversion coatings

Abstract

The corrosion protection performance of aluminum composite materials was investigated in 3.5% NaCl solution for time ranging between 1-60 days. Series of specimens were treated in molybdate solutions under different conditions. Free immersion and electrochemical activation techniques were used to apply the molybdate layer. The specimens which were directly treated or pickled before molybdate treatment showed severe pitting corrosion. Conversely, the specimens which were subjected to an oxide thickening step before the molybdate treatment showed outstanding corrosion protection. XPS revealed a higher amount of molybdate as MoO 42) for the specimens prepared by electrochemical activation technique than for the free immersion technique.

Techniques for synthesizing and applying smart coatings for material protection

“…Results confi rmed that self-healing is possible with conversion coatings other than those based on toxic hexavalent chromates and proved that when they are applied prior to an organic top coating (such as commercial fl uoropolymer, epoxy, etc. ), the coatings outperformed the commercially available coatings in electrochemical corrosion-resistance tests and exceed 2000 hours in the standard ASTM B117 salt spray test which enable them to be used in many industrial applications where active corrosion protection of materials is required [3][4][5][6][7][8][9][10][11][12][13] .…”

A review on the application of inorganic nanoparticles in chemical surface coatings on metallic substrates

“…MCC can produce a coating of insoluble molybdate, which has been applied on Mg, Zn, Al, and steel to improve their corrosion resistance. 79,[81][82][83] However, the major drawback of MCC coatings is the presence of pores and cracks, which lead to serious deterioration of this coating. Typically, an MCC coating presented a network feature, and there were many microcracks on the coating's surface (Fig.…”

Corrosion behavior of molybdate conversion coatings on AZ31 magnesium alloy in NaCl solution

“…Because of its strong oxidation character, its reduction product is stable and can form a passive film. Like chromate, molybdate acts as an oxidant in the chemical conversion treatment and its adsorbent product can inhibit the penetration of Cl 2 ions to protect the substrate (Hamdy et al, 2005). Recently, molybdate treatments have been applied on magnesium alloy to improve the corrosion resistance (Yang et al, 2008b, a;Wang et al, 2012).…”