Research On Preparation And Marine Biofouling Resistance Of Copperized Layer On Q235 Steel By Double Glow Plasma Surface Alloying

The adhesion of marine fouling organisms which causes damage or adverse effects has become an insurmountable obstacle to conquest the oceans for mankind.For postponing or inhibiting the Marine fouling organisms attachment In the first and second stages,the copperized layer is prepared by double glow plasma discharge technology,which aims at obtaining anti-fouling property and providing basic research for the follow-up projects on the surface of Q235 steel.The optimum parameters for preparing the copperized layer are exhibited:the source voltage is 900V,the sample voltage is 500V,the gas pressure is 35Pa,the distance of poles is 15mm,the holding time is 3h.by using test methods such as SEM,EDS and XRD and with thickness being the standard of measurement,it's determined that the layer is composed of two parts under the optimal process parameters:a 100?m outer sediment layer and a 40?m inner diffusion layer.And the energy spectrum analysis shows that the copper element is distributed in a gradient.In addition,from surface morphology,the surface of sediment layer is relatively rough and exists uneven cluster crystals which have gaps between 1?m to 5?m.By immersion testing,the constituent of outer rust layer of the matrix is?-FeOOH primarily.And because of the corrosion potential is relatively low,about-0.74V vs.SCE,?-FeOOH can not thicken on the surface but constantly transforms intoFe₃O₄.However,the porous and thin outer rust layer is constantly eroded to provide passageway for oxygen diffusion by relatively high Cl content in solution,which accelerates the corrosion of the matrix.Meanwhile,the corrosion behavior of the copperized layer is similar to the matrix.With relatively loose sedimental layer as well as the corrosion reaction is dominated by anodic dissolution of iron,the dense passivation film of copper is difficult to form but turn to produce iron products.Copper is present in solution mainly in the existence of ions.Subsequently,dissociative copper ions restrain the formation of the hydroxyl oxide and destroy the hydroxide bonds which refine the grain size and promote the formation of large and vertically oriented amorphous phases.Finally,the integrity of the copperized layer is broken.By marine biofouling resistance research,the exudation rate of copper ions is consistent with the corrosion behavior of copperized layer.Before the destruction of layer,the dissolution of iron is the primary anode reaction and the exudation rate of copper ions is only maintained near10?g·cm^-2·d^-1.However,after the destruction of layer,the levered sediment layer exposed to the solution directly and the exudation rate shows dramatical fluctuation which can reach137.4610?g·cm^-2·d^-1 maximally.Meanwhile,the growth inhibition experiment of nitzschia closterium indicates that the higher the concentration of copper ions,the shorter of 95%inhibition ratio reached.The nitzschia closterium can not exist for long in the environment containing certain level copper ions may results from the destruction to cell wall and enzymes which is necessary for metabolism by copper ions.