Preparation for painting and decorating Galvanised iron
You’re likely to find galvanised iron used as corrugated iron roofing, gutters and downpipes. The zinc coating on galvanised iron is to some extent ‘sacrificial’, so that if a small patch becomes damaged, the surrounding zinc will, in time, spread over to cover the damage.
But this weakens the coating and an application of paint will prolong its life. If the galvanising is new and bright, simply clean it with a rag dipped in white spirit or turps to remove any grease, and apply a calcium plumbate primer. If it’s old and greylooking, first remove any existing paint by rubbing lightly with a wire brush, trying not to scratch the surface. Then clean with white spirit or turps and apply zinc chromate primer.