Effect of stray current on corrosion of Q235,16Mn and X70 steels with damaged coating

The effect of stray current on corrosion of Q235,16Mn and X70 pipeline steels was studied by measuring the corrosion ratio, observing the surface, as well as calculating the variation of fractal dimension and corrosion pit depth with the change of the damaged rate of coatings. The results indicated that under the stray current disturbance,the degree of corrosion for Q235 was the most serious, 16Mn the next worse and X70 the smallest. As the intensity of stray current increased and the damaged ratio of coating decreased, the corrosion rate increased, the corrosion pit depth became deeper, and corrosion degree was aggravated. The fractal dimensions of the corrosion surface are determined by box-dimension method, which are found to be in agreement with the trend of measured corrosion rates, and in fact, the fractal dimension could describe the surface morphology of the stray current corrosion of pipeline steels.