Mitigation of corrosion-induced equipment loss in carbon steel in process industries using an indigenously developed acidic vapour–resistant primer

Acidic HCl vapours (e.g. from pickling or cleaning in refineries and chemical plants) aggressively attack carbon steels, yet conventional red-oxide primers offer only passive barrier protection and quickly lose adhesion in such low-pH environments. Here we demonstrate that embedding Ni-Al LDH nanoflakes into a standard red-oxide primer dramatically improves corrosion resistance of API 5L X70 steel in HCl vapour. In exposure tests, bare steel corroded at ∼1.76 mm/yr, whereas the LDH-modified primer showed essentially zero corrosion (∼0.0001 mm/yr) - an orders-of-magnitude reduction. Atomic force microscopy reveals the LDH-containing film is far smoother (Ra ≈66 nm vs 125 nm), and Kelvin probe measurements show a higher surface work function (10.5 eV vs 7.25 eV), consistent with a denser, more uniform barrier. This arises from the LDH's “ion-trap” effect: Cl-ions are captured in the LDH interlayers, blocking their ingress. The result is a more than five-fold increase in coating lifetime. Importantly, the LDH additive is blended into a standard primer without altering existing application procedures. This cost-effective modification provides a scalable route to greatly extend steel service life in aggressive acidic-vapour conditions.