Tailoring of Versatile Surface Morphologies on Hot Dip Galvanized Steel in Wet CO₂: Aspects on Formation, Barrier Properties, and Utilization as a Substrate for Coatings

Abstract

Zinc carbonate and a mixed-phase zinc carbonate were precipitated selectively on hot dip galvanized steel in the presence of CO and water. The zinc carbonate was precipitated as a uniform layer with cubic superficial appearance, while the mixed-phase zinc carbonate was precipitated as nanowires. The distinct structures could be formed separately or as a dual structure with nanowires on the outermost surface. The barrier properties were improved by the both patina forms; a significant increase in surface hydrophobicity was obtained. The dual patina structure was successfully coated with an organic coating, and the intact wet CO-induced patina with both structures was confirmed within the coating. The formed carbonates can be further converted to zinc oxide by calcination, preserving the delicate structures, which opens a wide range of potential applications for the nanostructured ZnO in a variety of future electronic and optoelectronic devices.

Corrosion mechanisms of Al‐alloyed hot‐dipped zinc coatings in wet supercritical carbon dioxide

“…[37,[40][41][42] A more detailed breakdown of the specific vibrations can be found in the literature. [43] These observations are consistent with earlier findings with early corrosion products being zinc hydroxycarbonate and the latter corrosion products (anhydrous) zinc carbonate. [44,45]…”

Assessment of pitting corrosion in bare and passivated (wet scCO2‐induced patination and chemical passivation) hot‐dip galvanized steel samples with SVET, FTIR, and SEM (EDS)

“…The interpretations of the spectra were based on the reference spectra of zinc compounds presented in previous publications. [ 16,20 ]…”

“…[ 15,17 ] Zinc patina layers possess high hydrophobicity, which could lead to an efficient barrier against metal corrosion. [ 20,22 ] In salt‐containing environments, complex zinc corrosion products (not Zn(OH) 2 or ZnO), possessing a negatively charged surface, have further been shown to aid in the repulsion of chloride ions [ 18 ] and increase the barrier effect against oxygen diffusion. [ 24 ] In other studies, this same phenomenon was confirmed by a decrease in oxygen reduction on the surface, measured as a decreased cathodic current, providing clear experimental evidence of the barrier effect.…”

Simulated rain exposures can mimic long‐term metal runoff at atmospheric conditions—A case study on naturally and prepatinated zinc sheet

“…The preparation of the P.Patina surfaces (P.Patina‐1 and P.Patina‐2) are described elsewhere. [ 18 ] A hot dipped galvanized surface was exposed in parallel and used as reference (Zn‐sheet), and to investigate how a fresh nonexposed Zn surface (with a thin surface oxide) differs from a naturally aged surface (N.Patina at repeated dry and wet conditions, e.g., during outdoor storage). The aged reference surfaces (N.Patina) were prepared by exposing fresh Zn‐sheet surfaces to repeated dry/wet cyclic exposures (3 h at 40°C/90% RH, 3 h at 10°C/90% RH, 3 h at 40°C/20% RH, and 3 h at 10°C/20% RH) in a Weiss WK3 340/40 climate chamber for 3 weeks.…”