Corrosion characteristics and random field model of corroded cold-formed thin-walled steel

The ST400 3D profiler is employed to scan the surface morphology of cold-formed thin-walled steel(CFTWS) sheets utilized in industrial settings for a decade to investigate the surface morphology characteristics of corroded cold-formed thin-walled steel structures. Surface morphology data of 6 specimens of corroded cold-formed thin-walled steel with varying degrees of corrosion are obtained. The characteristic parameters of general corrosion and pitting corrosion are extracted using the program, followed by probabilistic statistical analyses of parameters such as general corrosion depth, pitting corrosion depth, pitting corrosion diameter-to-depth ratio, and pitting corrosion volume ratio. The variation patterns of surface morphology characteristic parameters of corroded cold-formed thin-walled steel are investigated, and the relationships between corrosion characteristic parameters and mass loss rates are established. The results indicated that the general corrosion depth of cold-formed thin-walled steel follows a normal distribution, while the pitting corrosion depth and the ratio of pitting corrosion diameter-to-depth exhibited log-normal distributions. As the mass loss rate increases, the average value of general corrosion depth, the standard deviation of general corrosion depth, and the logarithmic mean value of pitting corrosion depth increase continuously, whereas the logarithmic mean value of the pitting corrosion diameter-to-depth ratio decreases. Under industrial corrosion conditions, pitting corrosion is identified as the most dominant type of corrosion in cold-formed thin-walled steel. As the degree of corrosion intensifies, the pitting corrosion shapes evolve toward a hemispherical form. Finally, a stochastic field model for general corrosion depth is developed based on the probabilistic statistical analysis results and the variation trends of the characteristic parameters.