Rust

Rust is the most common form of corrosion on roofing materials and the primary reason for the eventual failure of uncoated or under-protected steel roofing. The rusting process (technically called oxidation) occurs when iron in the steel reacts with water and oxygen to form hydrated iron oxide — the flaky, reddish-brown material we know as rust. Unlike the protective patina that forms on copper or aluminium, rust is porous and does not adhere firmly to the underlying metal, meaning it does not protect the surface — instead, it accelerates further corrosion by trapping moisture against the steel. On roofing, rust typically begins at the most vulnerable points: cut edges where the protective coating has been removed, screw penetration points where the coating has been damaged by the fastener, around nail holes on old galvanised roofs, and in areas where debris and moisture accumulate (such as valleys and behind parapet walls). Once rust begins, it spreads under the surrounding coating, lifting and blistering the protective layer and exposing more steel to the corrosive process. In Gippsland, rust is prevalent on the many galvanised iron roofs that are 30 to 60 years old — well beyond the typical lifespan of a basic galvanised coating. The region's high rainfall and humidity provide the constant moisture needed to drive the corrosion process. Town & Country Roofing assesses the extent of rusting during roof inspections and can recommend either targeted repairs (for localised rust) or a full roof replacement (when rust is widespread and the structural integrity of the sheets is compromised).