Effect of some N-heterocyclic inhibitors in the soldering flux on the corrosion behavior of eutectic Sn–58Bi alloy and its solder paste

The influence of some N-heterocyclic inhibitors on the corrosion behavior of Sn-58Bi alloy and powders in the soldering flux was investigated using electrochemical impedance spectroscopy (EIS), weight loss experiment and scanning electron microscopy (SEM). Results show that the piperidine-based inhibitor (P-1) acts as a good inhibitor on the corrosion of Sn-58Bi solder alloy and powders in the soldering flux. The inhibition efficiency (IE) improves with the increase in P-1 concentration. P-1 inhibitor also shows high protection efficiency for Sn-58Bi alloy corrosion in acid medium when the content of the organic acid increases from 2 wt.% to 6 wt.%. The SEM analysis results manifest that the Sn-rich phase of Sn-58Bi solder alloy is preferentially etched and greatly dissolved in the soldering flux without any inhibitor during immersion, and the addition of P-1 inhibitor can reduce the corrosion process significantly.