Clear Auto Finish for Exterior Wood?

Will an auto finishing product work on an outdoor wood project? Most finishers in this thread say not. June 28, 2005

Question
I am wondering if anyone has ever tried an automotive finish on wood? My partner and I are looking for an extremely durable finish for an outside project, and I was wondering about a clear auto finish. It works great on cars, what about wood? The client doesn't care what the finish is, just as long as it doesn't have to be done more than once. It's for quarter sawn white oak.

Forum Responses
(Finishing Forum)
From Paul Snyder, forum technical advisor:
Wood needs a lot of uv protection from the sun when it’s outside. Two years without maintenance (re-coating) is very good for a clear finish on wood - a year or less is typical.

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From contributor G:
I don't think an auto finish on exterior wood will work for long. The auto finishes are not flexible. As the wood expands and contracts, the finish will crack. It might not happen the first year, but it will happen.

My neighbor finished the clear redwood siding on his house with a clear 2 part catalyzed auto finish. Two years later, it was peeling off in strips. The same finish would have lasted 10 to 15 years on a car. I did a baltic birch chest which lasted about 3 years before the cracks looked really obvious.

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From contributor J:
I tried auto lacquer once on a cabinet and it peeled off in large sheets the very next week. I'll never do that again. I have been investigating using urethane because it is flexible enough, but I haven’t heard enough about it. I've heard it works good over bare wood, but I don't know about stained wood.