Effect of the inequigranular structure on corrosion resistance of the external surface of 0.2 PCT carbon steel pipes used in thermal power generation

The article considers the effect of the inequigranular structure of carbon steel 20 (0.2 wt. %C) on the electrochemical corrosion rate observed on the pipe outer surface of the dismantled panel heating surface. The morphological analysis of structural components of steel 20 was performed using the “Resource C7” metallographic analyzer of microstructure fragments of solid bodies. It was shown that due to the development of electrochemical corrosion the value of the inequigranular factor will determine the thinning speed of wall thickness, depth and width of inter-crystalline corrosion cracks. The higher is the given parameter (as well as grain structure uniformity), the lower is the general corrosion rate and the less is the depth and the width of inter-crystalline cracks developing from the pipe outer surface. The results obtained can be used to calculate the pipe residual life of heating surfaces.