We have a 30-year-old galvanized-steel door that's suddenly not holding paint. I used oil primer and numerous topcoats ... apply a product such as Klean-Strip Prep & Etch, a diluted form of ...

Let the siding dry for a few days before painting, beginning with an application of galvanized metal etching primer. Once the primer is dry, paint the house using 100 percent acrylic exterior paint.