MODELING AND OPTIMIZATION THE CORROSION OF PIPELINE X60 WELD BEAD USING BOX-BEHNKEN DESIGN

ABSTRACT: This study investigates corrosion degradation of the weld bead in API 5L X60 pipeline steel exposed to sulfuric acid under controlled hydrodynamic conditions, with the goal of developing a predictive model and identifying operating conditions that minimize corrosion rate. A three-factor, three-level Box–Behnken design (17 runs) was applied to quantify the effects of H₂SO₄ concentration (0.5–2.5), surface roughness (P200–p1000), and flow rate (100–400 rpm), while corrosion rate was obtained from electrochemical measurements using potentiodynamic polarization (Tafel) analysis. Statistical analysis showed that acid concentration and flow rate increase corrosion, whereas higher surface roughness tends to reduce the corrosion response within the investigated domain. A quadratic response-surface model provided strong predictive performance (reported R^2=0.9767) and enabled numerical optimization, yielding a predicted minimum corrosion rate of 9.095 mm/year at approximately H₂SO₄ = 1.078, roughness ≈ P400, and flow rate ≈ 137.1 (as reported). These results demonstrate that DOE-based response-surface modeling can efficiently map coupled operating effects and support parameter selection to mitigate weld-bead corrosion in aggressive acidic environments.