PREDICTIVE MODEL FOR EVALUATING CORROSION RATE OF MILD STEEL IN SIX ENVIRONMENTS

Abstract

Experiments were carried out in six environments for 90 days to determine the levels of corrosion rates on AISI 1021 mild steel rods. The environments were: Sodium hydroxide fumes sulphuric acid fumes; nitric and fumes; Sodium sulphate fumes; Sodium Chloride solution; and water from borehole. Weight losses in the rods were determined at intervals of 5 days as these rods were exposed to the environments. The relationships between loss in weight of the exposed steel and exposure period were determined. Corrosion rate models were developed as a function of total surface area and exposure period. The theoretical corrosion rates were compared to rates determined from theoretical considerations.

It was found that the corrosion effect is rapid in Na0H environment. Its effect was noticed after about 2 hours of exposure. The samples exposed to Sulphuric acid fumes environment had the highest mean corrosion rates of 0.5488 cm/yr (for established) and 0.5201 cm/yr (for predicted). Water from borehole environment had the least mean corrosion rates of 0.1249 cm/yr (for established) and 0.1277 cm/yr (for predicted). There is no significant difference between the calculated values of corrosion rates using established model and predictive models, thus indicating the reliability of the models.