Red rust on zinc/aluminium or aluminium/zinc alloy-coated steel
Red rust on zinc/aluminium or aluminium/zinc alloy-coated mild steel cladding
Causes
Corrosion of the steel when zinc/aluminium alloy coating has eroded to expose the steel
Cladding has run-off from translucent (PVC) sheeting
For factory coated material, wrong coating specification for the in-use conditions
Listed under: Exterior, finishes, metal, aluminium, steel, zinc, plastic, polyvinyl chloride (PVC), timber and wood-based, paint, timber, cladding, walls, durability, corrosion, rust, roof cladding, translucent sheets, wall cladding, profiled steel cladding
Cause
Corrosion of the steel when zinc/aluminium alloy coating has eroded to expose the steel
Repair
- sand the corroded areas to remove rust; prime with a zinc-rich primer and a metal primer, repaint applying a minimum two coats of acrylic paint, or in accordance with the manufacturer’s recommendations
- replace badly corroded sheets; ensure the new material is compatible with surrounding materials
Cause
Cladding material in contact with or has run-off from cedar or redwood, or timber treated with a copper-based preservative treatment
Repair
- sand the corroded areas to remove rust; prime with a zinc-rich primer and a metal primer, repaint applying a minimum two coats of acrylic paint, or in accordance with the manufacturer’s recommendations
- replace badly corroded sheets; ensure the new material is compatible with surrounding materials
Cause
Cladding has run-off from translucent (PVC) sheeting
Repair
- sand the corroded areas to remove rust; prime with a zinc-rich primer and a metal primer, repaint applying a minimum two coats of acrylic paint, or in accordance with the manufacturer’s recommendations
- replace badly corroded sheets; ensure the new material is compatible with surrounding materials
Cause
Corrosion of the steel in a highly corrosive environment such as a swimming pool, or in coastal, industrial or geothermal regions
Repair
- sand the corroded areas to remove rust; prime with a zinc-rich primer and a metal primer, repaint applying a minimum two coats of acrylic paint, or in accordance with the manufacturer’s recommendations
- replace badly corroded sheets; ensure the new material is compatible with surrounding materials
Cause
For factory coated material, wrong coating specification for the in-use conditions
Repair
- sand the corroded areas to remove rust; prime with a zinc-rich primer and a metal primer, repaint applying a minimum two coats of acrylic paint, or in accordance with the manufacturer’s recommendations
- replace badly corroded sheets; ensure the new material is compatible with surrounding materials
Cause
Inadequately primed end and/or side laps
Repair
- sand the corroded areas to remove rust; prime with a zinc-rich primer and a metal primer, repaint applying a minimum two coats of acrylic paint, or in accordance with the manufacturer’s recommendations
- replace badly corroded sheets; ensure the new material is compatible with surrounding materials
Cause
Cladding in ground contact
Repair
- sand the corroded areas to remove rust; prime with a zinc-rich primer and a metal primer, repaint applying a minimum two coats of acrylic paint, or in accordance with the manufacturer’s recommendations
- clear away ground in contact with the cladding; excavate adjacent soil to lower the ground level; slope ground away from the building
- replace badly corroded sheets; ensure the new material is compatible with surrounding materials
Cause
Insufficient rain washing
Repair
- sand the corroded areas to remove rust; prime with a zinc-rich primer and a metal primer, repaint applying a minimum two coats of acrylic paint, or in accordance with the manufacturer’s recommendations
- replace badly corroded sheets; ensure the new material is compatible with surrounding materials