The inhibitive performance of 2,3-pyrazine dicarboxylic acid and synergistic impact of KI during acid corrosion of 70/30 and 90/10 copper-nickel alloys

Pyrazine derivatives are efficient environmentally-safe chemicals for protecting metallic materials against corrosion during industrial acid cleaning. However, they have been mostly investigated for steel-based materials, which limits their versatility. Therefore, assessing their efficiency for protecting other important industrial alloys, like the Cu-Ni alloys employed in industrial heat exchangers, is also necessary. Herein, we investigated 2,3pyrazine dicarboxylic acid (PDA), singly and mixed with potassium iodide (KI), as a promising inhibitor against the corrosion of 90Cu-10Ni and 70Cu-30Ni alloys in 2% HCl. Based on short-term weight loss, electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization (PDP) measurements, an optimum PDA concentration (1500 ppm) impacted average of 39% and 55% on 90Cu-10Ni and 70Cu-30Ni, respectively. These values, however, depreciated slightly after 72 h. Through cooperative synergism, the addition of 5 mM KI significantly boosted PDA efficiency to 73% (90Cu-10Ni)/92% (70Cu-30Ni) at room temperature, and 51% (90Cu-10Ni)/63% (70Cu-30Ni) at 60 degrees C. PDA is a mixed-type corrosion inhibitor with slightly more anodic impact on 70Cu-30Ni but cathodic effect on 90Cu-10Ni. This mechanism translates into more efficient surface microstructural protection for 70Cu-30Ni than 90Cu-10Ni, based on SEM characterization.