Corrosion Behaviour of Iron Steel Bars on the Ghanaian Market; Elemental Composition and Mechanical Properties Perspective

Abstract

Corrosion is the main problem with structural iron steel bars. Iron steel bars undergo electrochemical reaction with its environment. The iron in the iron steel bar oxidizes to form iron (II) oxides, which is another stable form of iron. This means that the structural integrity of an iron steel bar is likely to weaken as time goes by. The aim of this research is to establish an elemental signature that will relate the mechanical properties of locally and imported 16 mm iron steel bars on the Ghanaian market to their sensitivity to corrosion to their elemental composition. Three iron steel bars brands labeled Local 1 (from Ghana), Foreign 1 (China) and Foreign 2 (Ukraine) were sampled for analyses. The samples were cut into 450 mm and their elemental composition, weight loss and mechanical properties such as ultimate tensile strength, yield strength and percentage elongation were tested at Ghana Standard Authority mechanical laboratory before and after corrosion. The Proton Induced X-ray Emission (PIXE) analytical technique method was used to analyze the samples, and the analyte sample was 16 mm iron steel bar mostly used in all building sites. The following elements, Chlorine, Potassium, Calcium, Titanium, Chromium, Manganese, Iron, Nickel, Copper, and Zinc were found present in all the three brands 16 mm iron steel. After the 60 days of immersion of the samples in 5 % NaCl solution the locally manufactured iron steel bar recorded an ultimate strength of 414.10 Nmm-2, the yield strength of 302.10 Nmm-2 and percentage elongation of 36.25 %. The Foreign 1 sample taken from China also had an ultimate tensile strength of 468.60 Nmm-2; the yield strength was 389.70 Nmm-2 and a percentage elongation of 22.50 %. The samples taken from Ukraine that was named Foreign 2, had an ultimate tensile strength of 528.60 Nmm-2, yield strength produced was 456.00 Nmm-2 and percentage elongation of 25.370 %. The results obtained showed a continuous decrease in mass of the iron steel bar samples with an increase in the immersion days. The overall results indicated that corrosion behavior of iron steel bar depends on the chloride ion concentration in the sample’s solution. The corrosion rate of the locally manufactured iron steel immersed in 5 % NaCl solution for 60 days was 0.07 mm per year and sample from China corrosion rate was 0.17 mm per year and the Ukraine sample had 0.16 mm per year. Though the locally manufactured iron steel bar recorded the lowest corrosion rate its yield strength dropped drastically as the immersion time increase. Chromium and Manganese were found to be the main elements that relate mechanical strength to corrosion rate of the iron steel bar.