Considering the cost – around €700 here in Spain – and taking my own age into account, I decided against it, as the frame would probably have outlived me by years. So I had to sand the entire frame down to see if it had any rust damage.
In fact, during my days of sanding, I discovered some rust damage, which I then treated as follows.
Since I was interested in how linseed oil, which is also the basis for Owatrol, worked together with varnish, I treated the struts I had additionally welded in with it.
It turned out that the linseed oil, which I had thinned with turpentine to speed up the hardening process, hardened into a solid layer after a few days, especially when varnished over it. For the primer, I used a two-component acrylic primer and applied two coats to the frame. After that, I varnished it with two coats of black polyurethane varnish from the marine sector, and my finish was perfect.
