In vitro corrosion behavior of Magnesium/2.5%HA biocomposites under different shot peening parameters

Abstract

The present study investigates the influence of shot peening on the corrosion resistance of Mg-2.5HA biocomposites within a simulated body fluid environment. Utilizing response surface methodology, this research examined the effects of shot peening parameters, including air nozzle pressure, nozzle-to-sample distance, and duration, on the biocomposites. Comprehensive microstructure observations, surface roughness assessments, and hardness evaluations were conducted on samples subjected to varied shot peening parameter settings. Corrosion tests revealed that samples peened at pressures of 2 and 3.5 bar for a duration of 1 min exhibited reduced corrosion rates of 5.96 and 5.47 mm/y, respectively, in comparison to the initial rate of 7.40 mm/y. It was observed that increasing nozzle pressure or extending peening duration led to a decline in corrosion resistance. The nozzle-to-sample distance, ranging between 90 and 130 mm, appeared to exert a negligible effect on the outcomes. The application of shot peening resulted in an accelerated formation of passivation layers, attributed to the presence of ultra-refined surface grains and increased surface roughness. In contrast, lower shot peening pressures and shorter durations yielded reduced surface roughness, thereby enhancing corrosion resistance. The response surface methodology model, developed to evaluate the 1-day corrosion rate and the pH of the simulated body fluid, demonstrated satisfactory accuracy with R-squared values of 89.07 % and 95.19 %, respectively. Consequently, an optimized shot-peening process can effectively regulate the degradation rate of Mg-based composite implants.