Study Of Water-line Corrosion Behavior Of Q235 Carbon Steel In The Static And Flowing Electrolyte

Corrosion attack under sea water is one of the most common kinds of damage for offshore structures.The ships and steel sheet piling are always exposed to sea water and atmosphere,while a water-line region exists around the air-liquid-solid area.Due to the combination effect of sea water and atmosphere,the water line area is apt to suffer severe localized corrosion.Therefore,the study of water-line corrosion mechanism is necessary to ensure the safety of the offshore structures and facilities.The area above and around the water-line are highly oxygenated and occupies a higher potential than the area below the water-line,which is less oxygenated.The large potential difference between different areas leads to serious galvanic corrosion and induces the failure of the marine structures.previous studies on water-line corrosion concentrated on the corrosion behaviors of water-line area in static environment.However,the influence of hydrodynamic conditions,which cannot be neglected in engineering practice,on water-line corrosion are rarely discussed,hence the behaviors of water-line corrosion is studied in this work.The water-line corrosion is a kind of localized corrosion.In order to understand the dynamic process of water-line corrosion,the wire beam electrode(WBE)is used to study the water-line corrosion in static and flowing environment.The details of this work and the results can be summarized as follows:(1)Firstly,the influence of hydrodynamic conditions on water-line corrosion of carbon steel is studied in the solution contains 3.5%(wt)NaCl.The results suggest that,under static solution,the anodic areas mainly gathered around the bottom of the samples while the cathodic area always appears at the water-line.However,in flowing solution,the galvanic current is higher than that in static solution and the localized corrosion is severe.Besides,the anodic and cathodic areas are staggered,with uneven distribution,which lead to a stronger galvanic effect and more severe local corrosion.(2)Secondly,the influence of hydrodynamic conditions on water-line corrosion of carbon steel is studied inartificial sea water.The results indicate that the anodic area and the cathodic area uniformly distribute in the static environment.However,the anodic area gathered near the water-line and the bottom area are cathodic area which almost suffered no corrosion.(3)The immersion tests were performed in both static and flowing solution using the samples which share the same dimension with the WBE.The results are in good accordance with that of WBE.