Verification and Improvements of Properties through Surface Treatment for Specific Applications : A comparative study of hardness, abrasion, friction, and corrosion properties for legacy and PFAS-free coatings

Sammanfattning

This project investigated whether key surface properties could be maintained or improved after removing PFAS-containing fluoropolymer topcoatings from Nedox® and Tufram® surface treatments. The study focused on four main properties: hardness, abrasion resistance, friction behavior, and corrosion resistance. These properties were evaluated using Vickers microhardness testing, Taber abrasion testing, static and dynamic friction testing, and neutral salt spray corrosion testing. The results showed that the different surface treatments performed differently depending on the tested property. The highest hardness values were measured for Nedox SF-2 and the modified Nedox 10K-3 process, where the nickel layer was hardened at 400 °C before polymer infusion. The PFAS-free Nedox FM-5 formulation exhibited hardness similar to that of the regular Nedox FM-5, indicating that PFAS removal did not significantly reduce hardness in this coating system. In the abrasion test, Tufram L-4 showed the lowest total mass loss and therefore the best abrasion resistance under the selected test conditions. The FM-5-based coatings showed the lowest static and dynamic friction values, but also the highest mass loss in the abrasion test. In the corrosion test, Tufram L-4 was the only surface treatment to show no visible corrosion after 168 hours of exposure. Overall, the results indicate that the most suitable replacement depends on the intended application. The FM-5-based coatings are relevant where low friction is the main requirement, while Tufram L-4 showed the most balanced performance when abrasion resistance, friction, and visual corrosion behavior were considered together. The modified Nedox 10K-3 process with a 400 °C heat treatment also exhibited strong hardness. The study shows that PFAS-free or modified alternatives may retain certain surface properties, but no single coating can be evaluated based on a single property.