Effect of ball burnishing process on surface roughness and corrosion behavior of S235JR steel

Degradation caused by corrosion is a major problem for S235JR steel and is responsible for many failures. Ball burnishing is a superficial mechanical finishing treatment that improves surface quality as well as its mechanical properties. The aim of this experimental work is to study the influence of this process on the surface quality and corrosion behavior of S235JR steel. The response surface method (RSM), based on Box-Behnken experimental design, was used to minimize the surface roughness, which has a significant influence on corrosion resistance. “Ra” and “Rz” roughness measurements, as well as 3D surface topography observations, were carried out. Furthermore, the subsurface microhardness distribution was examined, and an X-ray diffraction analysis was performed. The polarization technique (Tafel) and electrochemical impedance spectroscopy (EIS) were used to evaluate corrosion resistance. Finally, analysis by scanning electron microscopy (SEM) and energy-dispersive spectroscopy (EDS) was carried out before and after the corrosion tests. The results showed that burnishing force and ball diameter are the main parameters influencing roughness. The optimal regime reduced roughness “Ra” and “Rz” by more than 96% and 97% respectively, producing a smooth and uniform topography. XRD analysis revealed surface grain refinement without phase change. The subsurface microhardness increased to a depth of 40 μm, suggesting a burnished layer of equivalent thickness. Electrochemical corrosion tests and SEM observation showed that the corrosion resistance of the burnished surface was significantly improved, mainly attributed to grain refinement.