Research On Marine Atmospheric Corrosion Behavior Of A710 Steel And Its Welded Joints

The rapid development of the blue ocean economy puts higher demands on the performance of atmospheric corrosion resisting structural steel.A710 high strength weathering steel is a high-quality special steel developed in recent years.It is expected to be widely used in marine engineering machinery.In the practical application of A710 steel,the welding thermal cycle may lead to the change in the corrosion resistance of the welded joint,which has a great impact on its service safety.However,scarce researches have been carried out on the atmospheric corrosion resistance of A710 steel and its welded joints.In this paper,weight-loss method,macro/micro-electrochemical method,phase analysis and morphological observation were employed to investigate the long-term corrosion behavior of A710 steel and its two welded joints in simulated marine atmosphere environment.The galvanic corrosion kinetics of two welded joints and its influence on the corrosion resistance of welded joints were also discussed;The initial corrosion behavior of A710 steel in simulated marine atmospheric environment was studied by self-design capillary microelectrode technology and Scanning Kelvin Probe.This might provide data accumulation for the application of A710 steel in marine atmospheric environment.The main research progress and results are as follows:(1)Owing to the protective effect of rust layer on the substrate,the deceleration corrosion occurs in A710 steel in simulated marine atmosphere,and the whole corrosion process can be divided into two stages: a declining stage and a stabilizing stage.Furthermore,the enrichment of the alloying elements in the rust layer promotes the densification of the rust layer,which leads to the gradual stabilization of the corrosion rate of A710 steel in the second corrosion stage.(2)The selection of welding material and welding process has different effects on corrosion resistance of A710 steel welded joints.The regularity of corrosion resistance at the same corrosion time is followed as 80Ni1-H4 welded joint > A710 steel >WER70 welded joint.And the "small cathode and large anode" structure of 80Ni1-H4 welded joint is more conducive to practical engineering applications.(3)Due to the initial galvanic corrosion and the inhibition of the denser rust layeron the galvanic interaction,the variation of the galvanic current values of HAZ-BM and HAZ-WM couple in two welded joints of A710 steel can be divided into decreasing and stabilizing stage.(4)A710 steel exhibits selective corrosion of granular bainite during the beginning stage of atmospheric corrosion.With the increase of corrosion time,the uneven corrosion behavior of A710 steel shows homogenization and the corrosion tendency decreases gradually.