Preparation of corrosion-resistant hydrophobic composite films on magnesium alloy

Abstract

Magnesium alloy has attracted wide attention for excellent properties but poor corrosion resistance hinders its application. The method of preparing high-performance corrosionresistant films with low cost and easy operation is significantly crucial to the corrosion protection of magnesium alloy. By synthesizing zeolite film directly on AZ91D magnesium alloy, the work presented a simple, efficient and environmentally-friendly preparation method. In this study, a one-step synthesis method of multi-structure composite film on AZ91D magnesium alloy was explored. The prepared film surface had dense Mg(OH) 2 bottom layer and K 2 Al 2 Si 4 O 12 •xH 2 O upper layer with porous support microstructure. Compared with the substrate, the corrosion current on the sample surface modified by stearic acid was reduced by about three orders of magnitude, and the corrosion inhibition rate reached 99.96% with a stable contact angle of about 125°. The results showed the excellent corrosion resistance and stable hydrophobicity of the prepared sample.

Corrosion behaviour of facile coated ZnO on Mg–Zn–Zr alloy in Ringer’s physiological solution

“…The high phase angle values of the ZnO coated passive layer at the start of the test were due to the barrier-like effect created by the ZnO coating on Mg alloy, which prevented the Ringer's solution from making contact with the ZK60 free surface (i.e. a phase angle of 80° suggests that the metallic surface is adequately isolated from environment due to the presence of coating) [36]. The higher phase angle of 60° indicates the thickness of protective layer of ZnO and its adhesion to the substrate as compared bare alloy as shown in Figure 10(a and b).…”

“…It has been reported in previous studies that the development of metal chlorides on magnesium alloys in contact with simulated body fluid solution causes the corrosion layer to mechanically rupture because of higher molar volume of chloride ions [37]. The buildup of metal chloride at the metal interface should be taken into consideration as a promoter of the rupture of the oxide coating and in the nucleation and propagation of developing pits, even though the causes are yet unknown [36]. Therefore, one could presume that the significant Cl content in the form of magnesium chlorides salts, on ZK60 alloy after 48 h immersion in the Ringer's solution (37°C), promotes the formation of corrosion products with poorer protection properties and the increase in the tendency for pitting (Figure 13).…”