What is anti-rust treatment?

Anti-rust or rust protection covers a category of products applied to a car's undercarriage, cavities and weld seams to prevent corrosion. The most well-known product manufacturers include Dinitrol, Teroson and Mike Sanders.

The treatment typically takes place in a specialist workshop with a raised vehicle and high-pressure spray equipment. The product penetrates into the metal weld seams and forms a water-repelling, elastic film that prevents moisture from reaching the metal.

What does the anti-rust warranty cover?

A typical anti-rust warranty covers perforation of the bodywork within the warranty period, provided that:

  • The treatment was carried out at an authorised workshop
  • The vehicle has been inspected at the agreed service interval (typically every 2–3 years)
  • No mechanical damage has removed the treatment from exposed areas
  • The vehicle has not been in a saltwater environment without follow-up treatment

What does the warranty not cover?

  • Surface rust (rust bloom and rust that does not perforate)
  • Rust resulting from accidents, collision or mechanical damage to the undercarriage
  • Rust on untreated original rust spots that were present at the time of installation
  • Missed service visits (the most common reason for warranty lapse)

Documentation is everything

Anti-rust warranties are notoriously difficult to enforce without documentation. The manufacturer can reject a claim if you cannot prove: when the treatment was carried out, which product was used, which parts of the car were treated, and that the service intervals have been observed.

A digital certificate with timestamped images of the undercarriage, product specification and service history is the strongest documentation you can have.