AN EXPERIMENTAL INQUIRY INTO SURFACE ROUGHNESS OF PAINT-FINISHED MILD STEEL BY SOME TOP AUTOBODY SPRAY PAINTERS IN KADUNA METROPOLITAN AREA, NIGERIA

Abstract

Body finish appeal is one of the first noticeable things about any automobile. Most factory autobody painting is highly automated, so aesthetically appealing body finishes of high quality are efficiently achievable with high production rates. However, autobody painting for maintenance or repair in Nigeria is mostly done using manual skills and minimally automated facilities, with a high chance of ending up with low-quality or unappealing body finishes. The purpose of this paper is to present an experimental comparative study about the average surface roughness of paint-finished auto bodies by three top artisanal autobody spray painters, named MA Motors, Alsarafa Body Painters, and IBK Motors in Kaduna metropolis, Nigeria, relative to factory-painted vehicles at Peugeot Automobile Nigeria (PAN) Plc and relevant engineering standards. A cold-rolled mild steel sheet was procured for the study as the most common but corrosion-susceptible autobody material. The sheet was ascertained through nominal composition analysis and was used to produce four similar-sized sheet samples. The samples were individually taken to each of the spray painters and PAN, where they were surface-cleaned, painted, and cured according to the usual methods and standards used there in paint-finishing auto bodies. The surface roughness of the paint-finished samples was measured at 20 different points on each sample with the CRV-135 surface roughness tester and analyzed statistically in terms of the mean value (Ra), root mean square, depth to peak ranges, skewness, kurtosis, and variance. The obtained results indicated that the paint finishes from IBK Motors, Alsarafa Body Painters, MA Motors, and PAN had Ra values of 1.368µm, 1.4725µm, 1.6495µm, and 1.258µm, respectively. The analysis also indicated that all the paint-finished surfaces had minimal roughness, uncharacterized by excessive variations, peaks, and valleys, about their flat average values. The analysis finally indicated that autobody paint finishes by the spray painters are of similar and high quality by engineering standards and comparable to finishes at PAN. The paper provides useful insight into the surface roughness of paint-finished auto bodies by the spray painters as a fundamental quality control parameter that should be imbibed by all in the auto-body painting business, especially in Nigeria, to meet requirements by standards, customers, and users.