Preparation And Study On Tribocorrosion Properties Of Organic-inorganic Hybrid Phosphate Bonded Ceramic Coatings

Phosphate-bonded ceramic coatings are widely used in the surface protection of metal materials due to their low cost,simple construction,and green environmental protection.However,the majority of phosphate binders are fragile.The network structure generated by the phosphate binder is easily disrupted when external stress and corrosion act synergistically,resulting in a decrease in the wear resistance and corrosion resistance of the coating.Furthermore,the material loss mechanism of bonded ceramic coatings under the synergistic influence of friction and corrosion is poorly understood.Therefore,the organic-inorganic hybrid aluminum dihydrogen phosphate（AP）binder is prepared by adjusting the molecular structure of the phosphate binder in this paper.The pure wear,pure corrosion,and tribocorrosion behaviors of the AP coating and modified AP coating are carefully investigated,and the optimal quantity of AP in the coating is found,as well as the influence mechanism of hybrid AP on the coating performance.The following are the key research findings:（1）Study on the influence of AP content on the properties of bonded ceramic coatings.To begin,the curing mechanism of the ceramic coating is investigated by looking at its thermal characteristics and phase composition.Secondly,the effects of different AP contents on the friction behavior,electrochemical corrosion behavior,and tribocorrosion behavior of bonded ceramic coatings are studied.The results show that the whole curing process is an incomplete dehydration condensation reaction.Al PO₄ and Zn₃（PO₄）₂ are the main binder phases.The increase in AP content can promote the curing of the coating and improve the conversion rate of the curing reaction.The corrosion current density of the coating is smaller than that of the bare steel,and the protection efficiency reaches more than 97%.The impedance value increases first and then decreases.The total volume loss under the effect of tribocorrosion is greater than that under pure mechanical friction.Frictional behavior due to corrosion is dominant.It is discovered that the coatings improve tribocorrosion resistance when the AP content is 35 wt%.（2）Research on organic-inorganic hybrid modification of AP binder.Organic-inorganic hybrid AP binders are prepared through the hydrolysis condensation reaction of different contents of silane and AP binder.FTIR and XPS are used to study the chemical structure of the hybrid binder.The hybrid AP is introduced into the bonded ceramic coating,and its effect on the hardness,hydrophobicity and bonding strength of the coating is investigated.Experimental results show that MTES successfully chemically reacts with AP and introduces the-CH₃ organic group into the three-dimensional network structure of AP and forms a chemical structure with P-O-Si as the main body,which improves the molecular structure of the AP binder effectively.The hardness,hydrophobicity,and bonding strength of the coatings are improved by the hybrid AP binder,which is 53%,3.7%,and 38.7%higher than the pure AP coatings,respectively.Besides,the hybrid AP coating has a relatively obvious plastic yield stage,and the cohesion of the coating is significantly improved.（3）Study on the effect of hybrid AP binder on tribocorrosion properties of bonded ceramic coatings.The friction behavior,electrochemical corrosion behavior and tribocorrosion behavior of the hybrid AP bonded ceramic coating are analyzed.The results show that hybrid AP significantly improves the tribological properties of the coating.When the hybridization amount of MTES is 5 wt%,the friction coefficient and wear rate of the coating are the lowest.The corrosion current density of the hybrid AP coating is smaller than that of the pure AP coating.The results of tribocorrosion experiments show that the OCP value of the hybrid AP coating is high and stable.When the content of MTES is 5 wt%,the corrosion current density and the total volume loss of the coating is 62%and 64.8%lower than that of the pure AP coating,respectively.Synergy of friction and corrosion dominates total volume loss in hybrid AP bonded ceramic coatings and hybrid AP binders enhance the frictional corrosion resistance of coatings mainly by reducing both purely mechanical frictional behavior and corrosion-induced frictional behavior.