The coatability of oil, or of solvent-borne alkyd resin wood primers with waterborne acrylic finish is the subject of much debate, but not much information can be found in the scientific literature on this topic. The aim of our study was therefore to evaluate the adhesion strength of the waterborne acrylic coating on oiled wood or wood with a solvent-based alkyd primer and to test the recoatability of the oil-based primer with the solvent-borne finish. Since it is known that the performance of coatings on hydrophobic materials can be improved by plasma treatment of the material surface, our second objective was to evaluate the effect of low temperature atmospheric plasma treatment of the oil or alkyd primer on the adhesion strength of the acrylic or alkyd topcoat to the substrate with the primer. It was found that the oiled surface can be coated with the alkyd topcoat, while the adhesion of the waterborne acrylic topcoat to the oiled surface is worse. The compatibility of the waterborne acrylic finish with the alkyd primer is poor and such a combination is not recommended. Treatment of the oil primer with atmospheric low-temperature plasma improves the adhesion of the second alkyd or acrylic layer. However, when the alkyd-based primer was treated with plasma, the adhesion strength of the second coat to this primer became unacceptably low. To clarify this unexpected phenomenon, additional instrumented micro-scratch and micro-indentation tests were carried out. However, we were unable to find the reasons for this and this issue should be the subject of extensive future research.

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