Industry is seeking an improved assessment technique for its next generation metallic coated products

The challenge

Wet stack corrosion occurs on metallic coated products in wet storage conditions, resulting in the formation of unsightly corrosion products across the affected surfaces. The surface of metallic coatings are vulnerable to wet stack corrosion when, for example, the metal coated product is stored as a coil post manufacture or after post‐processing of the product into tightly nested profiles.

This research explores alternative surface treatment approaches to provide increased protection of metallic coated steel products in the downstream supply chain, as well as uniform weathering of metallic surface finishes post-installation. The development of more environmentally friendly and sustainable alternatives has been hindered by a lack of understanding of the wet stack corrosion process.

 

The response

PhD student Thomas Jurak and the Research Team within The Steel Research Hub (SRH), in collaboration with BlueScope, have developed a novel Electrochemical Noise Measurement (ENM) technique that simulates the wet stack environment and provides quantitative electrochemical data. There are significant advantages to using an electrochemical test; first, significantly faster testing times (hours rather than weeks) and second, quantitative electrochemical data can be used to study corrosion mechanisms and rates. Understanding the mechanism of wet stack corrosion is critical in the development of a suitable protective system, and accurate quantitative data is required for robust physical models. Unlike other electrochemical testing methods, ENM is achieved without the need for polarization of the sample, making the test non-destructive and permitting continuous monitoring over time.

A mathematical model was developed to demonstrate conclusively the effects of electrode impedance on noise data, which has important consequences for the use of ENM to assess real world corrosion events in the field. Field monitoring via ENM has been of interest for more than a decade now, and the model will help to progress this area of research significantly.

 

The impact

A mechanistic understanding of wet stack corrosion assists in developing alternative, environmentally friendly and nontoxic corrosion inhibitors to prevent wet stack corrosion of metallic coated products. Experiments utilising the novel ENM setup have provided insight into how wet stack corrosion progresses, as well as demonstrating the effectiveness of environmentally friendly alternatives to traditional chemical treatments. Furthermore, the team have developed a mathematical model validating the novel experimental method, with important consequences for the future of ENM and its use in measuring real world corrosion events.