Yes, I used McCloskey Man O War spar varnish recommended by Brian. 4 coats. Time will tell, but for now looks and feels very well protected. My coastal environment will certainly test this stuff.
Jon, that stuff as you know is pricey do you have enough left to do another set of the slats? I have no doubt its better stuff than the Helmsman interesting enough Valspar bought them out I was not aware of that.
Season after season, Man O'War stands up to what nature dishes out
Rain and moisture
UV rays from the sun
Coastal salt spray
Seasonal temperature changes
The strongest name in clear protection. Choose from gloss, semi-gloss or satin finishes, to beautify your interior and exterior wood surfaces for years with no cracking or peeling.
WHERE TO USE
Use on wood that needs protection from water, such as:
Exterior entry doors
Garage doors
Shutters, hand rails and trim
Outdoor furniture
Interior window sills and frames
Wood trim on boats (above the water line)
Wood projects, such has bird houses, mailboxes, planters, lamp posts
The coastal salt spray line should bode well for you.