Preparation for painting and decorating Metal and plastic windows
Metal doors and windows should be treated in the same way as metal pipes and gutters. So sand them down and make sure all rust is removed before priming. Aluminium frames can be left unpainted, but if you do want to paint them you must first remove any surface oxidation which shows as a fine white deposit.
Use a scraper or wire brush, but go very gently and try not to scratch the surface. Prime with a zinc chromate primer. Plastic window frames should not be painted.