Multi-objective optimization of corrosion current density and polarization resistance of surface-ground AA7075 thin plate in 3.5 wt.% NaCl solution

AA7075 thin plates are extensively used in the marine industry, particularly for the manufacturing of hydrofoil skin panels. Surface grinding is a critical finishing process for these plates, yet the optimal grinding parameters that minimize corrosion current density (Icorr) and maximize polarization resistance (Rp) are not well established. This study was conducted to determine optimal grinding settings for controlling Icorr and Rp in 3.5 wt.% NaCl solution (simulated seawater). AA7075 thin plates were ground following a design of experiments (DoE) schedule, and Icorr and Rp were measured using a CorrTest electrochemical workstation. Results showed that Icorr increased markedly with higher table speed (50 spm), feed rate (5.0 mm/min), and grinding depth (1.0 mm), while Rp decreased under the same conditions. Standardized effects analysis identified feed rate and grinding depth as the most influential factors, each with an effect of 10.94, whereas table speed had a moderate effect, and interaction terms played secondary but significant roles. Regression models demonstrated strong predictive capability, with R² and predicted R² values of 99.28% and 97.12% for Icorr, and 98.43% and 93.71% for Rp. The optimal settings were found at low table speed (2 spm), low feed rate (1.0 mm/min), and low grinding depth (0.2 mm).