Corrosion behavior of in-situ TiB2/7050Al cornposite in NaCl solution at different pH values

The polarization curve, electrochemical impedance spectroscopy (EIS) and static immersion test, combined with the microstructure characterizations, were applied to study corrosion behavior of the in situ TiB2/7050Al composite in NaCl solution at different pH values (pH = 4, 6, 7 and 10). The results show that the corrosion potential (E-corr) decreases with the increasing pH value. In accompany, the corrosion current density (I-corr) exhibits the minimum value at pH = 7, indicating that the composite is the least corrosive in neutral NaCl solution. In both acidic and alkaline solutions, the I-co(rr) values are rising to show the aggravated corrosion behavior. Analytically, the corrosion behaviors of the composite are different in acidic, neutral and alkaline NaCl solutions. In acidic (pH = 4 and 6) NaCl solutions, the composite has mainly experienced pitting behavior, and the pitting has mostly occurred around the TiB2 particle rich zone in the composite. In neutral (pH = 7) NaCl solution, the composite has suffered both slight pitting and uniform corrosion. In alkaline (pH = 10) NaCl solution, the composite has experienced uniform corrosion. The corrosion mechanisms are discussed in relation with the microstructure features for the composite.