When my original mudguards were about a year or so old I took them off expecting to give them a bit of a clean up and a rattle can paint job to stop the tin worm. Basically took one look at the state of them and got them grit blasted and powder coated. Also plugged up assorted cavities with epoxy metal and then several layers of stonechip paint on the insides. By the time another three years had gone by there was bubbling under the powder coating and one of them had broken at the rear mounting arm; this got welded up, failed again and fixed with a sleeve and more epoxy metal. Since then they have both been replaced with new, one due to hitting a tree (can't blame the powder coating for that one!) and the other just to match.
I'd be inclined to go with painting, at least it's easier to re-do when it inevitably fails and more corrosion emerges from the various unpaintable seams. I've also gone for anti-corrosion wax in the seams best as I can manage.
With a bit of luck G56 will come up with robust, non-corroding, lightweight mudguards that look acceptable before too long.
