Rust always starts where you can't see it. In sill cavities, along welds and behind wheel arches, moisture works its way through steel year after year. Cavity wax or oil-based protection stops that process from the inside: it fills gaps and displaces water before damage sets in.

Underbody coating handles the outside. Rubber or bitumen-based products absorb stone chips, reduce noise and keep salt and road dirt at bay. Whether you're treating a car preventively or restoring already-affected steel, the sequence is always the same: clean, degrease, protect.