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The 45 steel was sealing treated for various time in 6%(volume fraction)KH560 solution after the hot-dip aluminizing-anode oxidation. An Al-Al2O3-silane composite coating was formed on the surface of the 45 steel. The microstructure of composite coating was studied. The corrosion resistance of composite coating and its effect on the galvanic corrosion between the 45 steel and 30%(mass fraction)Cf/nylon6 composite were investigated. The results show that the silane coating effectively seals the cracks in Al2O3 coating, prevents the corrosive liquid from attacking the substrate. Hence, the corrosion resistance of the 45 steel is improved. Meanwhile, the good insulation property of the Al-Al2O3-silane composite coating can reduce the driving force of the galvanic corrosion between the 45 steel and 30%Cf/nylon6 composite, consequently, the galvanic corrosion resistance of 45 steel also is improved. After treated with the optimal KH560 treatment process for 5 min, the self-corrosion current density of the hot-dip aluminized 45 steel decreases by 3 orders of magnitude compared with that of the single hot-dip aluminized sample while the electrochemical impedance increases by 2 orders of magnitude, and the galvanic corrosion current density between the 45 steel and 30%Cf/nylon6 composite decreases by about 75%.

Herein, CoCrxCuFeMnNi (x = 0, 0.5, 1.0, 1.5, and 2.0, in molar ratio) high‐entropy alloys (HEAs) are prepared through vacuum hot‐pressing sintering. The influences of Cr content on the microstructure and the corrosion behavior in 3.5% NaCl solution are studied. The alloys are mainly composed of two face‐centered cubic (FCC) phases, namely, Cr–Co–Fe–Mn–Ni (or Co–Fe–Mn–Ni)‐rich FCC1 phase and Cu–Mn–Ni‐rich FCC2 phase. With the increase of Cr content, The FCC1‐phase area expands and the FCC2 phase area shrinks. In 3.5% NaCl solution, the corrosion current density (icorr) and average corrosion rate (Vcorr) of the HEAs decrease with the increase in Cr content. The icorr and Vcorr of Cr2.0 alloy are lower at 1.87 × 10−6A cm−2 and 0.02 mm year−1, respectively. The increase of transfer resistance (Rp) and decrease of relative thickness (CPE1−1) of the passivation film indicate that the more difficult it is for ions in the corrosive medium to pass through the capacitor layer, the better the corrosion resistance of the alloy. Improvement of the corrosion resistance is mainly due to the formation of denser Cr2O3 passivation film and reduction of the segregation degree of Cu in the FCC2 phase. [ABSTRACT FROM AUTHOR]

The hot dip aluminized ASTM 1035 steels (Al‐coated steel) underwent anodic oxidization, and various thicknesses of Al2O3 coating were applied to the surface of the Al‐coated steels (Al–Al2O3‐coated steel). The corrosion resistance of the Al–Al2O3‐coated steel was investigated using potentiodynamic tests, electrochemical impedance spectroscopy tests and measurement of galvanic current density in a bimetallic cell. It was found that the anodic oxidation resulted in the formation of a porous Al2O3 coating on the surface of the Al‐coated steel, improving both its corrosion resistance and galvanic corrosion resistance when coupled with carbon fiber reinforced nylon 6 composite (Cf/PA6). Silane treatment effectively sealed the pores within the Al2O3 coating, resulting in improved corrosion protection for Al–Al2O3‐coated steel due to the exceptional insulation, impermeability and hydrophobic properties of silane coating. Compared to the Al‐coated steel/carbon fiber reinforced polymer (CFRP) couple and Al–Al2O3‐coated steel/CFRP couple, stable galvanic current density decreased by approximately 75% and 45%, respectively. [ABSTRACT FROM AUTHOR]