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Synergistic effect of the composite corrosion inhibitor has been considered to be effective on most nonferrous alloys, such as aluminium and copper alloys. In this paper, we study the synergistic effect of TTA, BTA, and La3+ on Cu-Zn-Ni alloy. The composite corrosion inhibitors including the three components are prepared by using chemical methods. The results indicate that such composite inhibitors are very effective for Cu-Zn-Ni alloy against the NaCl solution corrosion.The influence of TTA, BTA and La3+on the performance of the inhibitor films has been comprehensively investigated. The weightloss experiment, corrosion test at constant temperature and certain moisture, and aerosol test are used to evaluate the effectiveness of the inhibitors. By using orthogonal design, the optimum concentrations of TTA, BTA, and La3+ for best protection are determined to be 14g/L,3g/L, and 7g/L, respectively. The synergistic effect between TTA, BTA, and La3+ for the composite inhibitors is evaluated by using electrochemical method. The XRD analysis and Roman spectroscopy are used to analyse the composition of the composite inhibitors, and explore the inhibition mechanism of the complex inhibitor layers on the copper alloy.The results indicate that the synergistic inhibitors of BTA+TTA or BTA+LaCl3 provide very good protective efficiencies for the copper alloy in 3.5% NaCl solution. But the mixture of BTA, TTA and lanthanum chloride （BTA:3 g/L, TTA:14 g/L, and LaCl3:7 g/L） provides the highest protective efficiency. The corrosion rate of the Cu-Zn-Ni alloy with the BTA+TTA+LaCl3 inhibitor coating in 3.5% NaCl solution at room temperature has been evaluated to be 2μm/year. These results reveal a significant synergistic effect between TTA, BTA, and La3+ for Cu-Ni-Zn alloy.
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