Estimation of Corrosion Rate of Mild Steel in Sea Water and Application of Genetic Algorithms to Find Minimum Corrosion Rate

Abstract

Life prediction of steel structure in marine environment is a challenging task for design and corrosion engineers for existing structures as well as new structures to be constructed. The rate of marine corrosion is a complex function of many parameters of fluid properties and chemistry of seawater. The major parameters influencing the rate are salinity, sulphate, bicarbonates, pH and temperature and dissolved oxygen. These parameters have a wide range of variation, depending on geographical locations of the structure as well as various depths of seawater in which parts of the structures are submerged. The inter-relationship among the parameters make it very difficult to establish a mathematical equation. It is also interesting to find a geographical location where rate of degradation of structure will be minimal. In the present investigation, endeavours have been made to estimate the corrosion rate for a given geographical location in an ocean with any combinations of these variables, by performing few laboratory experiments. Genetic algorithms have been applied with a combination of five genes: chloride, sulphate, dissolved oxygen, pH and temperature to obtain the optimum combination of these five parameters that would bring down the corrosion rate of steel to a minimum.