Protective Efficiency of the Oil Composition Coatings Against Carbon Steel Atmospheric Corrosion in the SO2 Presence
IFHAN 29-A shows the thickening ability with respect to industrial and transformic oils in the 293 – 353K temperature range. It allows to deposit the oil coating films of 20 ± 5 μm thickness on the metal surface. These films provide a protection of carbon steel against atmospheric corrosion in the presence of SO2. A growth of the inhibitor concentration in the oil composition film results a sharp increase of the protective efficiency in the presence of SO2 in comparison with the conditions without SO2. The oil nature doesn’t practically influence on the qualitative and quantitative character of the dependences. Protective efficience of the oil compositions reaches 80%.
Kinetics of the cathodic and anodic processes on steel has been investigated in the 0.5 M NaCl solutions in the presence of SO2. A growth of the SO2 volume concentration in the air phase increases the cathodic limiting diffusion current density in the absence of the protective oil composition film on the electrode surface, but does not practically influnce in the presence of the coating. A dependence of the anodic ionisation rate on the SO2 concentration in the presence of the protective oil composition film has an unmonotonous character.
The observed results are discussed with taking into account an interaction between SO2 and water leading to a formation of the SO2.H2O hydrate and the [SO2]/[H2SO3] correlation equal to 20 in the aqueous solution.