A Study On The Preparation Of Anticorrosion Coating For Titanium By Electrochemical Deposition

Titanium is a promising material to make bipolar plates in proton exchange membrane fuel cells(PEMFCs),because of its high electrical conductivity,excellent high specific strength and ductility.It also finds application in the field of biomedi-cine due to its good biocompatibility.However,titanium cannot well resist corrosion in the environment of PEMFCs and human bodies,which will cause negative effects.Coating protection is one of the most effective measures to protect titanium from cor-rosion.For the first time,a graphene layer on titanium is fabricated via electrophoretic deposition for the application to bipolar plates in PEMFCs.The graphene oxide(GO)was deposited on titanium at a constant voltage.Then the GO is reduced to graphene at 500℃in hydrogen atmosphere.The influences of the deposition voltage,the acid-ity of GO solution and the deposition time were investigated and we obtained the op-timal condition:the voltage was 10V,the acidity of GO solution was p H3.4 and the deposition time was 20min.The sample at the best condition showed a current density of 0.7μA/cm~2,which was an order of magnitude lower than Ti.However,the stability of the coating was low.The interfacial contact resistance(ICR)was 6.0mΩ.cm~2,which was very close to the department of energy 2020 target for PEMFCs’bipolar plates.In order to improve the anti-corrosion resistance and electrical conductivity of the coating,pulse electrodeposition was conducted to deposited GO on titanium under the voltage range 0～10V,p H 3.4,the pulse width 0.5s and the pulse cycle 1s.The sample prepared at this condition showed a current density of 0.25μA/cm~2 and the in-terfacial contact resistance of 4.0mΩ.cm~2,both of which met the department of energy2020 target for PEMFCs’bipolar plates.The diamond-like carbon(DLC)was electrodeposited on titanium under a con-stant voltage of 2.5V,with the formic acid or acetic acid aqueous solution as the elec-trolyte solution and carbon source.The influence of the volume fraction of formic ac-id and acetic acid on the structure and corrosion resistance of the DLC coated samples were investigated.The corrosion current of DLC coated titanium is one to two orders of magnitude lower than bare titanium sheet in simulated physiologic environment.It is also shown that both the organic acids and the graphite anode serve as the carbon source of DLC formed on titanium.