Taguchi Optimization Reveals pH as the Dominant Factor (85% Contribution) in Steel Oxide Film Growth

ABSTRACT This study systematically optimizes the galvanostatic formation of protective steel oxide films, a key process for enhancing corrosion resistance. Employing a Taguchi L 1 ₆ orthogonal array, we evaluated four critical parameters: boric acid concentration (0.001–0.1 M), applied current density (25–100 µA/cm 2 ), temperature (288–318 K), and solution pH (6.11–11.02) using oxide growth rate (dE/dt) as the kinetic response. Analysis of Variance (ANOVA) identified solution pH as the overwhelmingly dominant factor, responsible for 84.96% of the observed variation in film growth rate (dE/dt) underscoring its overwhelming control. A strong positive linear correlation was established, where each unit increase in pH accelerated the growth rate by 0.0248 mV/min. Consequently, the highest growth rates (0.285–0.3125 mV/min) were consistently achieved under alkaline conditions (pH 9.92–11.02). In contrast, boric acid concentration and current density had minor effects, and temperature was statistically insignificant. The resulting linear model, dE/dt = 0.0355 + 0.0248 pH, robustly confirms pH as the primary predictive variable. The integrated Taguchi‐ANOVA‐regression approach reduced experimental runs by 93.75% compared to a full factorial design, providing an efficient framework for industrial coating processes where precise pH management is paramount.