Chemical Analysis Of Selected Carbon Steel Artefacts From Benin City And Implications for Preservation

Abstract

The use of carbon steel in the fabrication of outdoor artefacts is widespread in Nigeria. The peculiar morphology of this material makes it susceptible to atmospheric corrosion, which ultimately can weaken and destroy carbon steel artefacts and consequently their embodied aesthetic and historic values. Using Benin City, taken to be representational of other metal artefacts fabrication contexts in Nigeria as case study, this study investigated the elemental composition of some carbon steels used in the fabrication of outdoor artefacts with a view to determining finishing options for the material to withstand corrosion. Three Ion Beam Accelerator techniques: Particle-Induced X-Ray Emission Spectroscopy, Rutherford Backscattering Spectrometry and Proton Induced Gamma-Ray Emission Spectroscopy were used simultaneously to determine the elemental composition of twenty three sampled items. Optical Emission Spectrometry was also used in determining the carbon content in the items sampled. Ten elements: C, K, Ca, Ti, Cr, Mn, Fe, Ni, Cu, and Zn were detected and measured. The carbon steels compositions, when compared with global standards, were found to be deficient. This raised issues on how such materials can withstand corrosion and corollary to which the study recommended the need for Nigeria to set standards for the quality of steel produced in the country and those imported into Nigeria. Significantly, the study also recommended a two-way coating, among other finishing options, to protect outdoor carbon steel artefacts from atmospheric corrosion and that, where one cannot get good quality standard carbon steels, an in-depth knowledge of preservation techniques becomes imperative.