When galvanised metal is stored while wet, a corrosion forms that is referred to as white rust. White rust is not truly rust, but it is still corrosion. The white powdery corrosion is zinc hydroxide and is the galvanised coating breaking down and separating from the surface of the metal. You cannot restore the natural appearance of the galvanised metal, but you can remove the white rust and still provide the protection that galvanising provides for carbon steel.
- Skill level:
- Moderately Easy
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Things you need
- Wire brush
- Clean rags
- Phosphoric acid
- Paintbrush (2-inch)
- Water hose
- Cold galvanising spray
Run the wire brush over the area that contains white rust to remove loose rust particles from the surface of the galvanised metal.
Wipe the wire-brushed surface of the metal with a clean rag to remove the loose white rust dust from the area to be treated.
Apply the phosphoric acid to the white rust with a two-inch-wide paintbrush.
Leave the phosphoric acid sit on the surface of the galvanised metal for three to five minutes.
Wash the phosphoric acid from the surface of the galvanised metal by thoroughly hosing the metal with water from the water hose.
Allow the galvanised metal to air dry, and inspect the surface to ensure that all the white rust has been removed from the surface of the metal. You may have to repeat the acid application and rinsing process multiple times to remove all of the galvanised rust. Each time you reapply the phosphoric acid, let it sit for a longer period of time.
Shake the can of cold galvanising spray and coat the area affected by the white rust to protect the base metal exposed by the galvanised rust.
Move the cleaned and re-protected galvanised steel after the cold galvanising spray has dried.
Tips and warnings
- Take extreme care when you are using phosphoric acid, as it can cause chemical burns, respiratory irritation and damage to common household materials.
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