The mathematical model of cathodic protection potential distribution with impressed current on the exterior of metal storage tank bottom is established and calculated by using Comsol multiphysics software. The effects of the numbers and layout of cathodic confluence points depth of auxiliary anode, soil resistivity, and the influence of polarization characteristic on protection potential distribution of tank bottom were studied. The results showed that, with other conditions unchanged, the way of setting confluence points on the center of tank bottom and more points confluence would produce better results of cathodic protection. But due to potential drop of tank bottom with little difference, and considering economic feasibility factors. Singlepoint confluence at the edges was proposed. Moreover, the smaller the soil resistivity was, the deeper the depth of auxiliary anode was. The tank bottom is not easy to be corroded and polarized. It is better for cathodic protection effect of tank bottom.

In Zhuangxi Oil Production Station crude stabilization tank as an example, studied the influences of the composition of the oil tank bottom water on oil tank bottom corrosion. Further studies on the mechanism of electrochemical corrosion with the method of polarization curves. Focus on the tank bottom water and various ion on the corrosion rate trend from electrochemical corrosion aspects and effect of ion coordonation. The results show that the stability of Cl-, Ca2+ content in Zhuangxi crude oil station is higher than other oil quality ,and the water quality can accelerated the corrosion rate of oil tank in a way.