Research Of Corrosion Dynamics Of Mild Steel Under Thin Electrolyte Layer Based On Random Corrosion Units Model

Mild steel is the most widely used metal in various industries, the loss caused by atmosphere corrosion over more than 50% the loss of mild steel corrosion every year. It is of significance to research atmosphere corrosion of mild corrosion in precaution and prediction. Most atmosphere corrosion experiment methods focus on corrosion data accumulating of long period, on the contrary, short period research of atmosphere corrosion is rare. Establish mathematical model is a effective way to research atmosphere corrosion of mild steel in short period.The essence of atmosphere corrosion is corrosion under thin electrolyte layer. The anodic process is solution of mild steel, the cathodic process is O2 depolarization. Corrosion rate is controlled by the rate of O2 depolarization. When there is no corrosion products on the surface, according to The Fick First Law, there is a linear relationship between limiting diffusion current density of O2 and corrosion products thickness; After corrosion products begin to cover mild steel surface, the diffusion of O2 through thin electrolyte layer convert to corrosion products layers. Due to the diffusion coefficient of O2 in corrosion products layeres is far lower than in thin electrolyte layer, the effective diffusion layer can be regarded as the corrosion products layers, the diffusion coefficient of O2 in corrosion products layers called apparent diffusion coefficient Dr, and Dr has no definite physical meaning to be measured. Treat corrosion products layers as a structure of maropore, based on the theory of macropore infiltration, bring experiential index,initial porosity and Ry amplified index three parameters into the model of Dr, then establish single corrosion unit model .With comparison to reference corrosion depth, using range analysis and variance analysis to compute reasonable numerical value range, then verify the value in single corrosion unit model in MATLAB.Due to defects on the surface of mild steel, the corrosion of mild steel under thin electrolyte layer is consisting of many random corrosion units, revise the single corrosion unit model with random function, verify the value of experiential index,initial porosity and Ry amplified index in random corrosion units model. Compute the corrosion data in short period based on the random corrosion units moedel.