Proper conservation of works of art is vital

New coating and application techniques to protect against corrosion

If there is anyone who can call himself an expert in the field of conservation of works of art, it is Prof. Arjan Mol of TU Delft. With artworks in our country undergoing maintenance at an ever-increasing rate, the expertise of Mol and his team is increasingly being requested. Beton & Staalbouw found Mol willing to shed light on the phenomenon of coating in relation to corrosion of metal artworks.

The problem of Chromium-6 coatings

"There are still Chromium-6 containing coatings that we encounter when maintaining or demolishing works of art," Mol opens the conversation. "When sanding or removing an artwork, you encounter that Chromium-6 coating. We now know how harmful the sanding dust that is released can be. In order to prevent health problems and not burden the environment, special technical, organizational and personal protection measures should be taken during renovation or demolition work. Now that we have entered the phase of increasing maintenance of artworks, attention to dealing carefully with Chromium-6-containing coatings is more important than ever." So caution is called for when Chromium-6 is involved. "Fortunately, these days we can work with pretreatments and coatings that no longer contain Chromium-6."

What do you recognize a bad coating by?

A coating may appear apparently good, but corrosion can fester under the skin, Mol says. "Fortunately, our monitoring techniques allow us to identify corrosion at an early stage, i.e., even before it is visually detectable. Many inspection companies are already working with the latest monitoring techniques. Think, for example, of electrochemical measuring methods. A combination of different analysis methods is often required. 'Hot spots' are searched with electrochemical techniques, but large areas are examined by using drones. The damage pattern is recognized by locally present color and reflection differences in the coating surface. Several market participants are well on track with this methodology."

On-site coating replacement

"When a coating needs to be replaced on site, we have to consider the limitations of working in the field," Mol outlines. "To get a robust adhesion on site, we usually have to apply different pretreatment and coating procedures than when we are preserving a new artwork in a factory hall. It's a challenge to do the right pre-treatment and coating in the field. Everything has to be top notch and optimal." When asked if the color of a coating affects its lifespan, Mol replied, "Not all pigments are equally UV- or chemical-resistant. Pigments interact with the polymeric matrix in a coating. If you change something in the composition or degradation results in detachment of the pigment-matrix interface, that can indeed affect corrosion resistance."

Coating as an integral part of service life prediction

A major proposal was recently approved by NWO (Netherlands Organization for Scientific Research), called "SUstainaBle and reLIable Macro stEel infrastructures (SUBLIME). Mol: "A collaboration between TU Eindhoven, TU Delft, TU Twente and the University of Leiden, with companies and agencies in the chain. We want to use Digital Twins and Artifical Intelligence to be able to link corrosion measurements to the remaining lifespan prediction of structures. In this way we move from monitoring to prediction and a coating can be included in condition-based maintenance management. Ergo: 'Get to work before the trouble starts'. Then we are not only talking about corrosion, but also about fatigue. We have managed to bring together a nice consortium, brimming with knowledge and practical experience, so that we can dive in well and deeply into the matter and tackle the issues with impact."