Corrosion protection of steel cut‐edges by hot‐dip galvanized Al(Zn,Mg) coatings in 1 wt% NaCl: Part I. Experimental study

Abstract

Corrosion of AlZnMg coated steel in chloride media is a complicated process, which progress is determined not only by the electrode reactions but also by the local pH and formation of soluble and insoluble corrosion products. In order to adequately describe and predict the corrosion behavior of steel/AlZnMg cut‐edge, a multi‐ion transport, and reaction model (MITReM) is built. Such model takes into account the transport of species in the solution together with their production/consumption in electrochemical and chemical reactions. The main aim of this work is the validation of a numerical model for describing and predicting corrosion of steel/AlZnMg cut‐edge in immersed conditions. This first part describes the experimental work done to obtain model input parameters and validation measurements. The metallic coatings are characterized experimentally with respect to their composition and microstructure, global and local electrochemical behavior (polarization curves, AESEC, and SVET). Local distribution of corrosion products and local pH are also characterized. No blocking effect of the precipitated corrosion products has been observed and dedicated measurements are performed to validate this observation. Based on the experimental input from this part, numerical models of cut‐edge corrosion with different levels of details are developed in Part II.

Changes in Corrosion Behaviour of Zinc and Aluminium Coatings with Increasing Seawater Acidification

“…Therefore, assessing changes in the service life of coating materials in a changing environment is crucial. Zn, Al, and Mg have anodic characteristics and are primarily used as coating materials to protect steel from corrosion in harsh environments [7][8][9][10][11][12]. Generally, zinc coatings show no significant changes in terms of their corrosion resistance in acidic and alkaline solutions (pH = 4-10) and, therefore, seem to be a good choice for undersea constructions [13].…”

“…Generally, zinc coatings show no significant changes in terms of their corrosion resistance in acidic and alkaline solutions (pH = 4-10) and, therefore, seem to be a good choice for undersea constructions [13]. However, to enhance the corrosion protection of Zn coatings in high-chloride and -acid environments, various types of Zn coatings with Al and Mg have been developed [7,8,11,12,[14][15][16]. For instance, 'Galfan' Zn coating, which was developed in 1980, contains around 5%wt.…”

Data-driven analysis of the local current distributions of 316L stainless steel corrosion in NaCl solution

“…However, as accurate measuring of corrosion depths is laborious and hardly automated, the datasets obtained are often speci c and limited in size. The ideal predictive modelling tool for pitting would rely on the early detection of localised corrosion [18][19][20] .…”