| Due to the excellent corrosion resistance,solvent resistance,fatigue resistance,weather resistance and heat temperature resistance,phosphate anti-corrosive coating is widely used in many fields such as marine ships,offshore oil production platforms and seaport engineering.However,there are some problems of poor wear resistance and erosion resistance of the coating,easy to fall off and lack of corrosion resistance in practical application.Aiming at the problem of easy corrosion and wear of marine equipment in service,in this paper,air spraying technology was used to prepare Al2O3 composite particles on the surface of 45#steel substrate to enhance the aluminum-based phosphate anticorrosive coatings.The purpose was to improve the wear resistance and corrosion resistance of the composite coating through the Al2O3generated in-situ and the added Al2O3 particles.The effects of Al2O3 sol contents and Al2O3 particle composition on the microstructure,mechanical properties,corrosion resistance,and wear resistance of the aluminum-based phosphate composite coating were investigated.The Al2O3 sol was added to the phosphate anticorrosive coatings,then Al2O3 reinforced aluminum-based phosphate composite coating was obtained by air spraying and thermal curing process.The effect of Al2O3 sol content(0?4wt.%)on the microstructure and properties of aluminum-based phosphate composite coating was investigated.The results show that Al2O3 sol experience the phase evolution process of Al2O3 sol?Al OOH?Al2O3(?-phase)during 500?thermal curing,and Al2O3 particles(Al2O3(s))generated in-situ appear to be dispersed in the coating.With the increase of the Al2O3 sol contents from 0wt.%to 4wt.%,the content of the amorphous phase in the coating decrease,the degree of crystallization increase,and the compactness improved.Besides,Al2O3 brought the particle strengthening effect to the prepared coating,resulting in the coating hardness enhanced from38HV to 65HV,and the bonding strength between the coating and the substrate increase from 15MPa to 25MPa.The self-corrosion potential of the coating increase from-714m V to-575m V and the self-corrosion current density decreased from 2.38×10-7A·cm-2to2.79×10-8A·cm-2,which indicated that the corrosion resistance is significantly improved.This can be attributed to the fact that the coating has a good shielding effect on the corrosive medium,thereby preventing the diffusion and migration of the corrosive medium in the coating,and thus lead to a decrease of corrosion rate,and the more moderate rust degree of the coating.The friction coefficient of the coating decrease from 0.756 to 0.654,the wear amount is reduced from 11.5mg to 8.9mg,and the wear resistance was significantly improved.Therefore,the coating has the best comprehensive properties when the Al2O3 sol content is 4wt.%.Al2O3 sol(Al2O3(s))and Al2O3 powder particles(Al2O3(p))were introduced into the phosphate anticorrosive coating to prepare Al2O3 composite particles reinforced aluminum-based phosphate composite coating.The effect of Al2O3 particle composition on the structure and properties of the aluminum-based phosphate composite coating was studied,and the anti-corrosion mechanism and wear mechanism of the coating were analyzed.The results show that Al2O3(s)or Al2O3(p)constituted form exhibit a limited improvement in compactness,bonding strength,hardness,corrosion resistance and wear resistance of aluminum-based phosphate composite coating,while these properties can be obviously improved by the aluminum-based phosphate composite coating formed by Al2O3 sol/Al2O3particles(Al2O3(sp)).At this time,the bonding strength of the coating is 30MPa and the hardness is 130HV.The self-corrosion potential reaches-522m V,and the self-corrosion current density is 1.68×10-8A·cm-2.In addition,the friction coefficient of the coating is 0.569,and the amount of wear is only 2.7mg.The anti-corrosion mechanism of the coating is the shielding effect of the coating and the sacrificial anode protection effect of the aluminum powder filler.The main wear mechanism of the coating is the abrasive wear caused by the friction and wear of Al2O3 particles. |
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