Enhanced corrosioon resistance by sol-gel-based ZrO2-CeO2 coatings on magnesium alloys

Abstract

The physical, chemical and mechanical properties of magnesium alloys make them attractive materials for automotive and aerospace applications. However, these materials are susceptible to corrosion and wear. This work discusses the potential of using sol-gel based coatings consisting of ZrO 2 and 15 wt.% of CeO 2 . The CeO 2 component provides enhanced corrosion protection, while ZrO 2 impart corrosion as well as wear resistance. Coating deposition was performed by the dip coating technique on two magnesium alloy substrates with different surface finishes: AZ91D (as-casted, sandblasted, and machined) and AZ31 (rolled and machined). All as-deposited coatings (xerogel coatings) were then subjected to 10 h annealilng: a temperature of 180 8C was applied to the AZ91D alloy and 140 8C to the AZ31 alloy. Morphological and structural properties of the annealed coatings were investigated by scanning electron microscopy, atomic force microscopy and transmission electron microscopy. Coating composition was examined using energy dispersive X-ray analysis. Adhesion of the annealed ZrO 2 -CeO 2 coatings on the substrates, assessed by scratch tests, showed critical loads indicative of coating perforation of up to 32 N. Hardness and elasticity, measured using depth-sensing nanoindentation tests, gave a hardness and elastic modulus of 4.5 GPa and 98 GPa, respectively. Salt spray corrosion tests performed on these coatings showed superior corrosion resistance for AZ91D (as-casted and machined) and AZ31 (machined), while severe corrosion was observed for the AZ31 (rolled) and AZ91D (sand-blasted) magnesium alloy substrates.

Corrosion resistance of sol–gel alumina coated Mg metal in 3.5 % NaCl solution

“…Singh et al [28][29][30] observed a significant improvement in the corrosion and pitting resistances of sol-gel alumina coated low carbon steel, 9Cr 1Mo ferritic steel and 304 SS in highly corrosive NaCl solution. In comparison, relatively few study has been reported in the development of sol-gel based ceramic oxides coating on Mg alloys [31][32][33][34][35][36]. Phani et al [35] developed sol-gel ZrO 2 and ZrO 2 -CeO 2 coatings on Mg based AZ91D and AZ31alloys.…”

“…In comparison, relatively few study has been reported in the development of sol-gel based ceramic oxides coating on Mg alloys [31][32][33][34][35][36]. Phani et al [35] developed sol-gel ZrO 2 and ZrO 2 -CeO 2 coatings on Mg based AZ91D and AZ31alloys. They found that both coated alloys showed superior corrosion performance in salt spray test.…”

Corrosion Resistance Improvement of Galvanised Steel by Doped Silane Pre-Treatments

“…Different additives have been used in the modification of silane films for improvement of their anti-corrosion properties in literatures (Shchukin, 2004, Kasten, 2006, Liu, 2006Phani, 2005and Pepe, 2001. Corrosion inhibitors, nanoparticle fillers, are doped into the silane coatings to enhance their corrosion resistant performance.…”

Hybrid sol-gel silica films with (TiO2-CeO2) binary nanopowders

“…The most common precursors for the hybrid films preparation include: phenyl-trimethoxysilane (PTMOS), methyltriethisxysilane (MTEOS), 3-glycidoxypropyltrimethoxysilane (GPTMS), trimethoxysilyl-propyl-methacrylate (TSPM), methylmethacrylate (MMA) and methacylic acid (MA) [1][2][3][4][5][6][7][8][9][10], as well as mixtures of organically substituted and unsubstituted Si-alkoxides.…”