3 questions on painting concrete and metal

Q. I have three questions about paint. In your Oct. 26, 1979, column you recommended three ways to paint a concrete porch: Concrete primer-sealer, fiber-glass and resin, and concrete stain. Which of the three do you suggest I use on my concrete porch?

* My 23-year-old metal garage door needs repainting continually. What should I use on the door to reduce the frequency?

* My new aluminum railing was sprayed with two coats of white paint about a year ago. It now is full or rust spots. Why? Mrs. Jessie Fowler Bradenton, Fla.

A. In reply to your first question, remove the old paint down to the clean concrete. I'd then apply a concrete stain instead of the other two methods.

* In regard to the metal garage door, first remove any loose and peeling paint by sanding, scraping, wire brushing, etc. Then I would apply a quality metal primer to a firm, thoroughly clean surface so as to obtain proper paint adhesion. Follow with a top coat in the sheen, color, and type of product you wish.

Note: Unaware of why the paint peels, I would defer to a local paint expert who can inspect the door and make his own recommendation.

* As to the aluminum railing, the chances are that the railing is not aluminum at all or it would not rust.Aluminum will not rust. The railing most likely is a ferrous metal which rusts because of an inadequate primer.

To retard the growth of rust short of sandblasting down to the bare metal, apply a full coat of rust-preventative primer to a clean smooth surface. Follow with an oil-based enamel top coat. This process usually is effective in curbing rust, but not always.