Multiscale and Multi-Technical Approach to Characterize the Hot-Dip Galvanized Steel Surface and Its Consequence(s) on Paint Adhesion and Tendency to Blistering

Krystel Pélissier,Dominique Thierry

doi:10.3390/coatings11060704

Abstract

It is well known that the surface state (cleanliness, composition) of galvanized steel prior to the application of an organic coating is an important parameter. The surface state will affect the adhesion properties of the complete system and therefore will also impact its corrosion resistance and its tendency to blistering. Before the application of a pretreatment layer, galvanized steel strips are normally alkaline cleaned. This step is known to remove the native oxide film formed on hot dip galvanized steel after processing and appears as one of the most important steps to study the impact of the surface properties on the performance of painted systems. This study focused on making use of the cleaning step to input a variability on the surface composition (mainly surface concentration of aluminum) and evaluate its consequence(s) on the performance of a complete paint system. The results showed that, a variability in terms of surface aluminum concentration could be achieved by the cleaning step and that signs of performance improvement in terms of adhesion and tendency to blistering were spotted with a low content of aluminum at the surface.

Highlights

Introduction and Tendency to BlisteringCoatingsDue to a small addition of aluminum (0.1–0.3 wt%) in the galvanizing bath, to its limited solubility in zinc matrix, and to its affinity to oxygen, the surface of hot-dip galvanized steel (HDG) is enriched in aluminum
Work performed by Kim and Leidheiser in the 1970s tried to assess the effect of the surface composition of HDG strips on paint adhesion [10,11]
By coupling surface characterization (Auger electron spectroscopy) to paint adhesion measured by the deformation test, they showed that the ability of HDG to retain paint deformation was at its maximum when low residuum of carbonaceous material and aluminum involved in the native oxide film at the surface were measured [10]

Summary

Introduction

Introduction and Tendency to BlisteringCoatingsDue to a small addition of aluminum (0.1–0.3 wt%) in the galvanizing bath, to its limited solubility in zinc matrix, and to its affinity to oxygen, the surface of hot-dip galvanized steel (HDG) is enriched in aluminum. By coupling surface characterization (Auger electron spectroscopy) to paint adhesion measured by the deformation test (wedge bend test, the O-T-bend test), they showed that the ability of HDG to retain paint deformation was at its maximum when low residuum of carbonaceous material and aluminum involved in the native oxide film at the surface were measured [10]. To affect the adhesion properties of the complete system, the surface state of HDG steel will impact its performance related to corrosion resistance and its tendency to blistering. Recent studies have highlighted the impact of the distribution of the pretreatment layer on the tendency to blistering and were able to partially link it to the presence of the native aluminum oxide film at the surface [12,13,14,15,16,17]

Methods

Results

Conclusion