The safety of steel structures is of paramount importance in construction engineering and maintenance management. Corrosion causes strength deterioration and weakening of aged steel structures. Thus, if the right material is not selected for a particular application, the consequence of corrosion results in great losses, hence an investigation of the effects of annealing, normalizing, tempering and hardening heat treatments on the corrosion susceptibility of 0.17%C High Strength Low Alloy Steel in sea water was studied in this work. The samples were machined into cylindrical pieces of 16mm diameter and 40mm long and were properly labelled for easy identification. The non-heat treated and heat-treated samples were cleaned, weighted and immersed in sea water for various durations of 15, 30, 45, 60, 75 and 90 days. The optical micrographs were taken of the samples. The assessment of effect of corrosion on the steel samples used was carried out via weight loss at various exposure times which lasted for a maximum duration of 90 days. The weight losses were evaluated and used to determine the corrosion penetration rates of the samples in the medium. The results obtained shows that the corrosion rates for the samples are highest during the initial stages and thereafter reduce with time. The normalized sample shows a lower corrosion penetration rate of 6.40E-05 mg/cm2/year when compared to other samples studied. Also, the normalized samples show a lower weight loss of 0.3 and hence corrode less while the control shows a higher weight loss 0.88.