Study On Galvanic Corrosion Behaviors Of TA2 Titanium And Dissimilar Metals

Titanium and its alloys have a wide application prospect in ship field because of their excellent corrosion resistance to seawater.Although the electrode potential of titanium itself is low,its oxidation film properties can promote the formation of stable passivation film,which makes titanium has excellent corrosion resistance.However,the electrode potential of natural oxidation film on titanium surface is very high and the insulation property of the film is poor,so the metal material component with low electrode potential couple with titanium in seawater or other corrosive media is easy to be corroded by galvanic corrosion.The galvanic corrosion caused by titanium components severely limits the application of titanium in the field of ship,so the surface electrical insulation of titanium becomes the key technology for its wide application in the field of ship.In this paper,TA2 titanium was electrically insulated by electrochemical oxidation（anodic oxidation and micro-arc oxidation）to investigate the effect of oxidation treatment on the galvanic corrosion behaviors of titanium and dissimilar metals.Firstly,the galvanic corrosion behaviors of TA2 titanium coupled with three materials（316L stainless steel,5083 aluminum alloy,B10 copper alloy）was studied.The effect of the area ratio of anode and cathode,the distance between anode and cathode and the soaking time on the galvanic corrosion of different three pairs of material was investigated.The study results suggested the galvanic current of the three pairs increased with the increase of the area ratio of anode and cathode and the decrease of the distance between anode and cathode.The corrosion speed of three materials were accelerated as anode after coupling with TA2.The corrosion situation of 5083 aluminum alloy by galvanic effect was the most serious.A large corrosion pit was formed on its surface.Secondly,the surface of B10 copper alloy showed uniform corrosion.The accelerate corrosion of 316L stainless steel by galvanic effect was the least,and the pitting pit size only increased slightly compared with the self-corrosion.After anodic oxide film was prepared on the surface of TA2 titanium and sealed,the galvanic current of the three pairs decreased significantly compared with the corresponding bare metal pair(The current densities of three couples of 316L stainless steel,B10 copper alloy and 5083 aluminum alloy decreased from 0.199,0.127 and 3.248μA?cm^-2 to 0.014,0.034 and0.503μA?cm^-2,respectively),which could be reduced to the level of the self-corrosion current density.We can draw a conclusion the sealed anodic oxide film can effectively inhibit the galvanic corrosion of the three pair of materials because of its good electrical insulation performance.The galvanic current densities of the three pairs were significantly lower than those of the corresponding bare metal pairs after the micro-arc oxide film were prepared and sealed on the surface of TA2 titanium The sealed micro-arc oxidation film can also effectively inhibit the galvanic corrosion of the three pairs of materials.In general,sealing the oxide film to improve the electrical insulation performance of the film is very important to inhibit the galvanic effect of the three pairs.Especially for the 5083aluminum alloy pair,the sealing treatment of oxide film is particularly important.The unsealing oxide film can accelerate galvanic corrosion due to the existence of a lot of micro-hole defects.Comparing with the sealed micro-arc oxidation film,the sealed anodic oxidation film had a more stable inhibition effect on the galvanic corrosion of the three couples,which was correlated with the film forming mechanism and microstructure characteristics of the two oxide films.The study results of TA2/5083 aluminum alloy pair suggested that the galvanic current was obviously lower when the cathode and anode were oxidized and insulated simultaneously than when the cathode and anode were oxidized and insulated separately.It can be seen that the electric insulation treatment for both cathode and anode can better restrain galvanic corrosion effect.