A: I’ve seen a lot of evidence that tin siding can be repainted, although I haven’t found much information on how to do it.
I had tin gutters — actually terne, a zinc/tin alloy — on my turn-of-the-20th-century former house. The experts recommended Tin-O-Lin, which I bought at a Philadelphia roofing supplier, a slow-drying linseed oil-based primer and finish coat recommended for spot priming exposed and rusted areas.
It was not recommended for anything but roof applications. When I checked recently to see if the recommendations had changed, they had not.
I would assume that the same instructions for painting aluminum would apply to tin, and I am referring to the procedures established by the Dow Paint Quality Institute in Spring House.
Treat any mildew with a 3-to-1 mixture of water to household bleach, leaving it on for 20 minutes and adding more as it dries; wear eye and skin protection. Rinse thoroughly.
If there is any white oxide on bare metal, remove as much as possible by rubbing with nonmetallic scouring pad. (If steel wool is used, residual particles, if not completely removed, can eat pin holes through the aluminum.)
Remove dirt, chalk, treated mildew, etc., by scrubbing with detergent and water, and rinse thoroughly; or, power wash with plain water. Chalking on weathered aluminum siding tends to be deep in the factory finish, and a second treatment may be necessary.
Priming the old factory finish generally is not necessary if chalk can be removed as part of surface preparation.
For areas where chalk is stubborn and cannot all be removed, apply a solvent-based exterior primer recommended for this substrate.
For areas where metal is exposed, remove any white powdery oxide with a nonmetallic scouring pad, and apply a latex or oil-based exterior metal primer that is recommended for bare aluminum. Do not leave a primer unpainted.
Use top-of-the-line, exterior 100 percent acrylic latex house paint in flat or satin finish, depending on appearance desired. A flat finish will be much less revealing of dents and irregularities in the siding than will a glossier finish.
For best results, apply by spray.
I don’t know the extent to which your house has been insulated, since it was built in 1950, but if you choose to replace the tin with vinyl, you might want to tighten it up.
©2012 The Philadelphia Inquirer
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