Optimizing the corrosion resistance of additive manufacturing TC4 titanium alloy in proton exchange membrane water electrolysis anodic environment

Titanium alloys are commonly used as the bipolar plate material in proton exchange membrane water electrolysis (PEMWE). However, traditional machining methods are difficult to process titanium alloy parts, which further increases the cost of bipolar plates. The wire-arc directed energy deposition (WA-DED) additive manufacturing (AM) technology is low cost and high utilization of material. However, the undesirable microstructure always restricts the performance improvement. In this work, the electrochemical corrosion and passive characteristics of wrought TC4 and WA-DED AM TC4 alloys in the simulated PEMWE anode environment were investigated. The microstructure of AM TC4 alloy was optimized and the corrosion resistance was enhanced by heat treatment. The results indicate that the corrosion resistance of AM TC4 alloy is better than wrought TC4 alloy, and appropriate heat treatment can further improve the stability of passive film. Compared to wrought TC4, Ti -/f phase fraction of AM TC4 decreased from 9.6 % to 1.3 %, and the heat treatment further reduced Ti -/f phase fraction of AM TC4-850 and AM TC4-1050 alloys to 0.8 % and 0.1 %. The passive film thickness of wrought TC4, AM TC4, AM TC4-850, and AM TC4-1050 alloys calculated with the Power-Law model were 0.5 nm, 1.76 nm, 1.94 nm, and 2.02 nm, respectively. After heat treatment of 1050 degrees C, AM TC4-1050 alloy exhibited the best corrosion resistance, showing the lowest corrosion current density of 54 mu A/cm2 and the lowest passive current density of 19.5 mu A/cm2. Moreover, Ti oxide contributed most to the composition of passive film. In AM TC4-1050 alloy, the percentage of Ti oxides was 80.9 %, showing the best corrosion resistance.