Response of corrosion level in galvanized steel submerged in insitu sea water to the influence of contact time and iron exposure
AO Ekete, CI Nwoye
This paper presents the response of corrosion level in galvanized steel submerged in insitu sea water to the influence of contact time and concentration of iron exposure. SEM analysis of the corroded steel surface revealed deposit of white strip-like waxy rust and dark-grey corrosion products on the zinc surface. Variation in this deposit indicates variation in the level of corrosion attacks on the zinc and invariably on the steel structure. The corrosion level of the galvanized steel increased with increase in both the contact time considered and concentration of exposed iron. This is because incessant natural agitation of the sea water does not allow formation of (ZnOH)2 which is alkaline nature, due to uniformity in sea water pH. An empirical model; ? = 0.0117 ?2 – 1.7742 ? + 0.05? + 109.8125 was derived, validated and used for the response analysis of the corrosion level. The validity of the model was rooted on the core model expression ? -109.8125 = 0.0117 ?2 – 1.7742 ? + 0.05? where both sides of the expression are correspondingly approximately equal. The standard errors incurred in evaluating the response of corrosion level in the steel to the influence of contact time and concentration of exposed iron as obtained from experiment, derived model and regression model were 1.3, 0.65 & 1.33 and 2.83, 2.23 & 2.8 % respectively. Maximum deviational of model-predicted corrosion level from experimental results is less than 3%. This translated into about 97% operational confidence and response level for the derived model as well as 0.97 reliability response coefficient of the corrosion level to the collective operational contributions of contact time and concentration of exposed iron.