Road salt (primarily sodium chloride, NaCl, sometimes calcium or magnesium chloride) is spread on roads during winter to lower the freezing point of water and prevent ice formation. While essential for road safety, it is one of the most damaging contaminants a vehicle encounters — accelerating corrosion of metal components, undercarriage, and brake systems.
Why road salt is so destructive:
- Corrosion catalyst — salt solution is a strong electrolyte that dramatically accelerates electrochemical corrosion of steel, aluminium, and brake components.
- Penetration — salt spray reaches every crevice: wheel arches, door sills, underbody panels, and brake assemblies.
- Persistence — dried salt residue continues absorbing moisture from the air, keeping surfaces in a corrosive wet state.
Washing off road salt:
Road salt is water-soluble but often mixed with organic dirt and road grime that requires chemical assistance. A thorough winter wash should include:
- A high-pressure pre-rinse focusing on the undercarriage and wheel arches.
- Active foam application to dissolve the organic binder layer.
- A thorough rinse, ideally followed by an acidic step to remove any remaining mineral deposits.
In winter months, washing frequency should increase — ideally after every significant salt exposure. Products with corrosion inhibitors like Fortis Foam PRO provide additional protection. For seasonal wash strategy, see car wash seasonality.