Dear Haupert, based on your response just now, I called the company Supergrip and inquired. Unfortunately, I have to tell you that hydrofluoric acid solutions or similar do not react with wood. You are probably right with your statement that they change the surface structure, but only on mineral substrates, according to the statement from Supergrip. I will probably decide on the coating that the company offers. However, I first have to properly steam the wooden floorboards on the terrace and then apply herbicides / fungicides. After that, the coating will go on top.