Bilt Hamber Dynax S50 | Cavity Wax Corrosion Inhibitor
The one with the test data
Every anti-corrosion product claims to work. Dynax S50 is the one with a 42-page independent report behind it, and it is publicly hosted.
The University of Hertfordshire, School of Engineering & Technology (Report PG-BH13/001, Dr Phil Green, 2013) ran a 2000-hour cyclic salt spray test based on ASTM B117-03 — 5% NaCl fog, cycled 10 minutes wet / 50 minutes dry at 35°C — with film thickness matched at roughly 50µm across every product tested. Dynax S50 ranked first, ahead of Mike Sanders Korrosionsschutzfett (which was applied at 500µm — ten times the film), Auson Noxudol 700, Rustbuster Mil-Spec, Dinitrol 3125HS and Waxoyl.
The honest caveat, which we'll give you rather than bury: the study was commissioned by Bilt Hamber. Independent laboratory, sponsored research. That's a meaningful distinction and you should weigh it. It's still vastly more evidence than any competitor in this category has put on the table.
What it does
S50 is a solvent-borne wax that creeps. It wicks into welded seams, lap joints and surface defects — the places corrosion actually starts — and leaves a soft, brown, wax-like film that self-heals if it gets disrupted. That self-healing property is the entire reason it belongs in a cavity: a box section is a place you cannot inspect and cannot re-treat easily, so the film has to close itself back up when a stone or a bolt scrapes through it.
Bilt Hamber describe the corrosion inhibitors as "highly polar" and "metal-seeking." They don't disclose the chemistry and neither will we — you'll find people online confidently naming the wax. They're guessing.
The numbers
Target film thickness around 50µm. Roughly 50% solids. Flash point 44°C. Stores up to five years unopened between 5–30°C.
How to use it
Atomise into the cavity through the 600mm extension wand supplied with the aerosol. If the surface is wet, pre-treat with Ferrosol to displace the water first. Then the critical step almost everyone gets wrong: leave the cavity open for 48 hours so the carrier solvent can escape before you refit the bungs. Seal it early and you trap solvent against the steel.
Cold product gets thick. Condition it at around 15°C for 24 hours before use.
Handle it properly
Aerosol, LPG propellant. Danger — H220 (extremely flammable gas), H280, H304 (may be fatal if swallowed and enters airways), H315, H336, H411. Ventilation, no ignition sources, respiratory protection if you're spraying volume.
Safety Data Sheet (Australia)
Download the Bilt Hamber Dynax S50 SDS (PDF)