Electrochemical Corrosion Behavior of Stainless Steels and Titanium in a New Absorption Heat Pump Medium

The electrochemical behaviors of four stainless steels (S1, S2, S3 and S4) and titanium material (S5) in a new heat pump medium (potassium formate solution) were studied by tests of polarization curves and electrochemical impedance spectroscopy. The results showed that the self-corrosion current density of five materials in 80% (mass fraction) potassium formate solution increased with the rise of temperature, the corrosion current density of S5 titanium material was the highest, and that of S1 stainless steel was the lowest. S2, S3 and S4 stainless steels exhibited good corrosion resistance when the temperature was below 125 ℃, and their self-corrosion current density increased rapidly when the temperature was relatively high. The self-corrosion current density rank of the five materials was S5≈S4,S3,S2,S1 when temperature below 100 ℃, S5, S4,S3,S2,S1 when temperature above 100 ℃. The charge transfer resistance R_ct of S5 was the largest, followed by that of S4, S3 and S2, and that of S1 was the smallest.