| In recent years,with the development of science and technology,human exploration and demand for the ocean have continued to deepen.However,because the marine environment is very harsh,the structural properties and corrosion and pollution resistance requirements of steel used in marine facilities such as ships are extremely high.In particular,the adsorption and corrosion of steel by marine microorganisms is one of the issues that need to be solved urgently.Therefore,research on improving the surface corrosion resistance and antifouling performance of steel surfaces is of great significance.In this paper,the corrosion and fouling problems of marine steels in actual working conditions were studied.Atmospheric plasma spraying technology,plasma enhanced chemical vapor deposition technology and plasma nitriding technology were used to prepare plasma spraying(Ti O2,Co-based,Ni-based)coatings,Si-DLC films and nitriding layers on the surface of AH32 steel.SEM,AFM,Raman spectroscopy,roughness measuring instrument,contact angle measurement,erosion corrosion and electrochemical methods were used to characterize the surface morphology,roughness,composition,hydrophobic performance and corrosion resistance of the coating,and the related mechanism was also discussed.Corrosion process and corresponding mechanism,and electrochemical monitoring methods were used to characterize the microbial adhesion and corrosion mechanism of plasma spray coating.The main progress made in the paper is as follows:The hydrophobic coatings prepared on the surface of AH32 steel by plasma spraying and their corrosion resistances were studied.It was found that the plasma spray coating significantly improved the hydrophobic properties of AH32 steel.Co-based coatings and Ni-based coatings had a static contact angle of more than 130° with water,and both have good hydrophobic effects.All three coatings improved the corrosion resistance of AH32 steel significantly.The three coatings significantly improved the seawater erosion resistance of AH32 steel.The corrosion weight loss rate of plasma spraying Ni-based coating was the smallest,and the corrosion current densities were the lowest.The hydrophobicity and corrosion resistance of Si-DLC films with different Si contents were studied.It was found that with the increase of Si content,the surface roughness of the film decreased,the sp3 bond content increased,the sp2 bond content decreased,the ID/IG decreased,and the hydrophobic properties improved.All three films significantly improved the corrosion resistance of AH32 steel,of which Si-DLC film with 13.35% Si content had the lowest corrosion rate and the best corrosion resistance.The effect of nitriding time on the hydrophobicity and corrosion resistance of the nitriding layer on the surface of AH32 steel was studied.It was found that the surface roughness of AH32 steel was significantly improved after nitriding,and the contact angles were higher than 120°.The surface roughness of the sample with a nitriding time of 4 hours was the largest,which is 205 μm,and the contact angle with water reached to 145°.Nitriding has significantly improved the corrosion resistance of AH32 steel.Among them,the nitriding time is 4 hours.AH32 steel has the lowest corrosion rate and the excellent corrosion resistance.Electrochemical monitoring was used to study the microbial corrosion process of plasma sprayed coating on AH32 steel.It was found that the corrosion behavior of coatings and substrates were significantly different in artificial seawater and natural seawater.In the initial stage of natural seawater immersion,the adsorption of microorganisms can cause the coating potential to decrease.In the later immersion period,the corrosion rate of the coating was increased due to the accumulation of microorganisms in the rust film.The corrosion behavior of hydrophobic materials during immersion is mainly affected by their corrosion products. |
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