Dual-functional coatings with hydrophobic and anti-corrosive properties on Mg alloys via PEO and CoFe-LDH/myristic acid modification
Mohammad Aadil, Talitha Tara Thanaa, Christopher Alma Suranto, Mosab Kaseem
Abstract
This work presents a dual-functional coating strategy for AZ31 magnesium alloy, designed to achieve hydrophobic and anti-corrosive properties through plasma electrolytic oxidation (PEO), CoFe-layered double hydroxide (LDH) deposition, and myristic acid surface modification. The PEO process generated a porous oxide base layer, which served as a template for the hydrothermal growth of LDH, enhancing surface uniformity and structural integrity. Subsequent dual post-treatment with myristic acid and cobalt nitrate led to the in situ formation of cobalt myristate, forming a chemically bonded hydrophobic barrier atop the LDH layer. This top layer significantly improved surface hydrophobicity, achieving a contact angle of ~ 131°, compared to ~ 113.5° for LDH(M) and ~ 81.3° for the PEO-only sample. Electrochemical testing revealed that the cobalt myristate-modified coating exhibited the lowest corrosion current density (3.48 × 10 −11 A/cm 2 ) and the highest top layer impedance (3.81 × 10 7 Ω/cm 2 ), confirming superior corrosion resistance. Furthermore, density functional theory (DFT) calculations showed that the M-Co complex had a significantly reduced HOMO–LUMO gap (2.89 eV) compared to myristic acid (6.34 eV), indicating improved charge transfer ability. The M-Co complex also exhibited stronger adsorption on Co-CoFe LDH with a vertical adsorption energy of − 44.87 kcal/mol, highlighting its enhanced interaction with the surface. This multifunctional coating platform holds great promise for next-generation protective interfaces on lightweight magnesium substrates.