Study On Surface Quality And Corrosion Resistance Of AH32 Steel Rust By Nanosecond Pulse Laser Cleaning

Laser cleaning is a novel removal technology of decontamination/rust,removing materials by melting or gasification under the laser irradiation.It has the advantages of controllability,high efficiency and environmental protection.In recent years,it has attracted great attention from scholars at home and abroad.In this paper,the surface rust of AH32 marine steel was studied.Laser cleaning experiments were carried out with nanosecond laser,and the surface micro-morphology/roughness/hardness tests were carried out.The effect of laser cleaning on the corrosion resistance of AH32 steel surface was explored through electrochemical corrosion test.The main work is as follows:(1)Based on the principle of metal corrosion,the composition and structure of the rust of AH32 marine steel was analyzed,revealing the formation mechanism of the rust.Based on the physical-chemical principle of solid interface and the model of particle adhesion force,the Van der Waals force,capillary force,electrostatic force and ion bonds formed by iron ions combined with other elements between the rust and matrix were analyzed,aimed to deduce the model of adhesion between the mentioned above.Besides,the thermal/mechanical effect in the process of nanosecond pulsed laser cleaning were analyzed based on the interaction mechanism between nanosecond pulsed laser and material,describe the process of removing rust on the surface of AH32 marine steel under the action of nanosecond pulsed laser induced heat/force.(2)Laser cleaning process test was carried out via step-by-step de-rusting method,based on the 1064 nm Nd: YAG nanosecond pulsed laser.Laser confocal microscopy,Microhardness tester,scanning electron microscopy and X-ray energy spectrum analyzer were used to detect the surface morphology/roughness,microhardness,micromorphology and material composition after laser cleaning,in order to establish a clear quality evaluation system.The effects of process parameters on surface roughness,microhardness and micro-morphology were studied to reveal the rust removal mechanism of nanosecond pulsed laser.(3)The electrochemical corrosion behavior of cleaned samples with different laser parameters(laser power and scanning speed)in NaCl solution was studied.Polarization curves,electrochemical impedance spectroscopy,bode diagram and corrosion surface morphology were analyzed,and the influence of process parameters on the corrosion resistance of the cleaned surface was studied.The results showed that laser cleaning can reduce the surface roughness,improve the hardness and corrosion resistance of AH32 marine steel.Compared with untreated specimens,the surface roughness of the cleaned specimens decreased by 38.1 % and the surface hardness increased by about 5.7 % when the laser power was 20 W(after 60 W laser cleaning)and the scanning speed was 3000 mm/s.Besides,the corrosion potential shifted positively by 13.6 %,and the range of passivation potential increased by 17.2 %.The passivation current density decreased by 50.3 %,and the breakdown potential increased by 56.6 %.Generally,the cleaned specimens showed nice corrosion resistance.