Gravimetric corrosion monitoring and mathematical fitting of atmospheric corrosion data for carbon steel

The corrosion of carbon steel was studied in different atmospheres at sites in the Basque Country. A bilogarithmic law relating weight losses and exposure time is proposed. Coefficienss a and b in the basic equation were formulated as functions of the measured atmospheric parameters. The system of equations was solved by a multiple linear least squares regression. The final equation In p = 2·689 + 2·784[SO2]0.4 + 3·102[NaCl]0.6 + 0·846 In tw − 3·853[SO2]0.5[NaCl]0.6 − 0·212 In t + 0·024[SO2] In t−0·32[NaCl] In t + 0·381[SO2][NaCl] In t − 0·178tw In t, where p is penetraiion (μm) and t and tw are total exposure and time of wetness (years), fits the experimental results with a correlation coefficient of 0·985. Its predictive power, using results from the literature, was good when the environmental parameters were in the studied range.