Inhibiting effect of Benzotriazole on the stress corrosion cracking of Cu-27%Ni cupronickel and Cu-30%Zn brass in Mattsson’s solution

The performance of Benzotriazole (BTA) as a stress corrosion cracking (SCC) inhibitor is investigated for Cu-30Zn and Cu-27Ni alloys in Mattsson’s solution using electrochemical techniques and slow strain rate test (SSRT). With the addition of BTA, the polarization resistance increases for both alloys. Electrochemical impedance measurements show that BTA can form a protective film on the surface of the Cu-27Ni alloy and shifts the corrosion potential to nobler states. BTA also improves the corrosion resistance of the Cu-30Zn alloy by controlling the cathodic reaction rate and charge transfer resistance. SSRT results reveal that the presence of BTA decreases the susceptibility to SCC for both alloys; this improvement is more significant for Cu-27Ni alloy. Fractographic analysis after SSRT confirms that crack propagation regime is controlled by the BTA concentration. For Cu-27Ni alloy, fracture type changes from intergranular brittle to ductile as the protectiveness of BTA increases. Besides, BTA recovers the ductility by decreasing crack tip dissolution and growth as fewer cracks are observed around the necked area of fractured Cu-30Zn alloy tensile sample.