Enhanced Corrosion Resistance of SUS304 Stainless Steel via Atomic Layer Deposited Al2O3/ZrO2 Nanolaminates

Atomic layer deposition (ALD) was employed to fabricate single-layer Al2O3, single-layer ZrO2, and Al2O3/ZrO2 nanolaminate coatings on SUS304 to enhance corrosion protection in chloride-containing environments. All coatings were deposited at 250 °C using optimized self-limiting ALD processes, and the total film thickness was controlled at approximately 54 nm for a fair comparison. Structural characterization revealed that Al2O3 films remained amorphous, whereas ZrO2 films exhibited a thickness-dependent transition from amorphous to crystalline phases. In the nanolaminate structures, thinner ZrO2 sublayers (<9 nm) retained amorphous or locally nanocrystalline characteristics, while thicker ZrO2 sublayers (15 nm) developed polycrystalline features with increased grain boundary density. Electrochemical corrosion tests conducted in 3.5 wt% NaCl solution demonstrated that the Al2O3/ZrO2 nanolaminate coatings exhibited significantly lower corrosion current densities and delayed pitting corrosion compared to single-layer coatings. Among all samples, the [Al2O3 (15 nm)/ZrO2 (3 nm)] × 3 nanolaminate showed the best corrosion resistance, with the lowest corrosion current density (Icorr = 6.20 nA/cm2) and the highest protective efficiency (98.34%). These results highlight the critical role of nanolaminate architecture and sublayer crystallinity in suppressing ionic diffusion and provide an effective strategy for designing ultrathin, high-performance corrosion barrier coatings for stainless steel.