The Study Of The Galvanic Corrosion Behavior Between The Carbon Steel And Stainless Steel In Marine Environment

Twenty-first Century is a crucial period for China to develop marine economy rapidly.Marine engineering equipment is the technological base for capture marine resources and developing marine economy.Various gases and a large number of salts dissolved in seawater.This resulted in the ocean becoming a very corrosive environment for all kinds of marine structures made up of steels.Carbon steel and stainless steel have excellent economic performance and load capacity,and they are widely used in the field of Ocean Engineering.The study of corrosion behavior and galvanic corrosion of common carbon steel and stainless steel in seawater environment has important guiding significance for corrosion protection of marine structures.In this paper,pitting corrosion behavior of 304 and 316 L stainless steels in different marine environments and the uniform corrosion behavior of X65 steel in different marine environments were investigated by electrochemical measurements.The potential difference and kinetic parameters between carbon steel and stainless steel were analyzed by polarization curves.Galvanic corrosion behavior of carbon steel and stainless steel was investigated by galvanic current measurement and wire beam electrode measurement technique.Besides,the surface topography was analyzed by electron microscope,and the main conclusions are drawn as follows:?1?Polarization curves,impedance spectra and surface morphology analysis show that pitting corrosion is the main characteristic of 304 and 316 L stainless steel in different concentration of Cl-solution,and Cl-concentration has a significant influence on their corrosion resistance.When Cl-and SO₄^2-coexist,the content of Cl-plays a dominant role in pitting corrosion of 304 and 316 L steel.This is because there is a competitive relationship between Cl-and SO₄^2-,which leads to the failure of SO₄^2-to dominate in the cathodic process.When Cl-and SO₄^2-coexist,the corrosion resistance of 316 L is higher than that of 304 stainless steel.?2?For X65-304 and X65-316 L galvanic couples,with the increase of single Clconcentration or single SO₄^2-concentration,the coupling potential of two kinds of galvanic couple decreases,the galvanic current increases,and the corrosion increases.And in a certain concentration of Cl-solution,adding SO₄^2-will further aggravate the corrosion.?3?For X65-304 and X65-316 L galvanic couples,when the concentration of single Cland SO₄^2-are equal,the galvanic current in the former environment is greater,the corrosion pit is larger,and the corrosion of Cl-on galvanic pair is stronger than that of the same concentration of SO₄^2-.?4?In the same solution environment,the X65-316 L galvanic couple has more obvious galvanic effect than the X65-304 galvanic couple.The coupling potential of X65-316 L couple is lower,the galvanic current is greater,the corrosion pits are obviously larger,and the galvanic corrosion is more severe.?5?The potential and current diagrams of the electrode show that when the X65 carbon steel and 316 L stainless steel are coupled,the maximum anode current becomes smaller and the corrosion tends to be more uniform.However,the corrosion area increases and corrosion intensifies,X65 steel is the anode of the battery.The conclusion is consistent with the analysis of the corrosion morphology of the electrode surface.?6?In galvanic corrosion,the area of 316 L stainless steel is bigger,the corrosion of X65 steel stabilizes more quickly,and with the cathode area increases,the maximum anode current increases rapidly,the total galvanic current increases,corrosion rate increases.