Evaluation of microstructure and corrosion performance of cold gas-sprayed Al and Al-50Al2O3 composite coatings on AZ31B magnesium: a comparative study

• Innovative approach of deposition of Al and Al-50wt% Al₂O₃ composite coatings on AZ31B magnesium alloy substrates using cold gas spray (CGS) technology is introduced. • Increasing gas pressure and standoff distance reduces porosity in Al coatings by 1.5% to 2.7% and in Al-50Al₂O₃ coatings by 0.1% to 1.8% • Electrochemical measurements revealed that the corrosion rates for Al and composite coatings were 90.7 and 10.5 times lower than that of the AZ31 substrate, respectively. • Comparative analysis of the corrosion performance between Al and Al-50Al₂O₃ coatings demonstrated that the icorr and Rct values of the Al coating were 10.5 times lower and 13.8 times higher, respectively, than those of the composite coating. This study evaluates cold gas sprayed (CGS) Al and Al-50wt%Al₂O₃ coatings on AZ31B magnesium substrates at different standoff distances (10, 20, 30 mm) and gas pressures (10, 20, 30 bar). Increasing gas pressure and standoff distance reduced porosity in Al coatings from 4.6% to 1.9%, and in composite coatings from 5.2% to 3.4%, due to higher particle impact velocities and deformation. Higher porosity in composite coatings is attributed to porosity within Al₂O₃ particles. Corrosion tests on optimized coatings (30 bar, 30 mm) showed corrosion rates 90.7 times lower for Al and 10.5 times lower for composite coatings compared to uncoated AZ31B. Charge transfer resistance was 102 times higher for Al and 7.6 times higher for composite coatings. Better corrosion resistance of Al coatings is linked to the mechanically bonded Al–Al₂O₃ interface, which in composites may create channels for corrosive agents, accelerating localized corrosion.