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Self-repairable Zinc-free Weldable Anti-corrosion Primer for the Steel protection

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Prime time for steel protection

The EU-funded WELDAPRIME project has developed a thin protective steel primer which retains good weld-through capability and corrosion protection, as well as being zinc-free and cost-effective.

Industrial Technologies

Anti-corrosion protection of carbon steel and mild steel is critical to meet both quality and cost considerations. Protection is necessary for when the steel is in use but also during its transportation and storage, usually involving the application of primer coatings. However, most weldable primers usually have limited corrosion protection and are often applied too thickly (25-50 microns) to allow quality welding. Whereas, thinner primers (under 25 microns) often end up with negligible protective properties. These primers currently in use also contain high zinc content, presenting a significant health hazard when welded. The WELDAPRIME project has succeeded in exploiting sol-gel technology organising molecules to produce a primer which offers durable corrosion protection; resistance to mechanical damage; at an affordable cost; without the health hazards of traditional primers which contain zinc, while also crucially maintaining quality welding. Harnessing ‘sol-gel’ technology The starting point for WELDAPRIME was the knowledge that most steel primers actually have poor adhesion properties, coupled with the fact that most corrosion takes hold at cracks within the coating. Understanding that the answer to avoiding these problems lay in the molecular structures and chemical bonds of the primer mix, the project team used so called ‘sol-gel’ techniques to create a primer based on the manipulation of nano-particles. However, while the general behaviour of nano-particles can be predicted to a degree, their specific interactions are more difficult to predetermine. The project response was to mitigate uncertainty by using two completely different formulations during the assessment work. The team then agreed on a single formulation for the industrial scale-up, trial application and associated welding studies. The resultant primer displayed both excellent adhesion to the substrate as well as good adhesion to the top-coat. The WELDAPRIME team also succeeded in fabricating these thin zinc-free coatings while also reducing impact on the welding characteristics of the protected substrate. Indeed, as the project coordinator Professor Luisa Coutinho summarises, ‘After welding, the part did not display corrosion meaning that the primer - even after welding - was still acting as a barrier to corrosion.’ The WELDAPRIME primer can be applied by either brush or spray (both conventional and airless). Additionally, as the solvent content has limited VOC (volatile organic compounds) emissions, the primer is in compliance with European regulations for primers applied to buildings on-site. Getting ready for market The WELDAPRIME team have already been in talks with interested companies and to encourage widespread adoption of their innovation have been further tweaking the formula. As Prof Coutinho further explains, ‘The existing formulation still requires a lot of time for preparation and curing. As this was not a priority concern for industry, based on our survey, it was not a focus area in the project. Nevertheless, we are already working on industry-friendly improvements to increase the appeal of our solution.’ The market for WELDAPRIME’s innovation is significant, as steel (especially carbon steel) is in wide use across a range of sectors; including those of the oil and gas, chemical, construction and marine industries. Global steel production is estimated to be around 1400 million tons (around 145 million tons in Europe, in 2011) and said to be worth nearly EUR 1 trillion.


WELDAPRIME, anti-corrosion, primer, anti-rust, coating, nano-particles, steel protection, sol-gel, welding, adhesion,

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18 January 2023