DINITROL: what it is and which products we use
DINITROL is a range of automotive rust protection products made by DINOL GmbH, of Lügde, Germany. At Arctic Works we use three DINITROL products, in this order: Penetrant LT on existing rust and in the seams, 4942 as a thick layer on the whole underbody, and 4010 Corroheat in the cavities. Each one does a different job, so they don't replace one another.
The three products at a glance
| Product | Where we use it | What it does | Thickness recommended by the manufacturer | Salt spray test (datasheet) |
|---|---|---|---|---|
| DINITROL Penetrant LT | on remaining rust, in seams, in cavities | creeps into gaps, stabilises rust, drives out water | 100 µm wet, 40 µm dry | over 1,000 h at 40 µm dry |
| DINITROL 4942 | on the whole underbody | thick bitumen-based layer, resistant to stone chips | 500-800 µm wet, 300-500 µm dry | over 2,000 h at 500 µm dry; in two layers, up to 3,000 h |
| DINITROL 4010 Corroheat | in cavities: chassis rails, sills, crossmembers, doors | hard, transparent, heat-resistant waxy film | 120 µm wet, 40 µm dry | 500 h at 50 µm / 1,000 h at 100 µm / 1,500 h at 150 µm, after drying for 24 h at 80°C |
What the salt spray test figures mean
The salt spray test (ISO 9227) keeps a metal panel coated with the product in a closed chamber, in a fog of salt water, and counts the hours until rust appears. It's a laboratory test, useful for comparing products with each other, not a promise of how many years the treatment will last on the road.
An hour figure only makes sense together with the thickness it was measured at. That's why we always give the two as a pair.
For 4010, the datasheet figures start at 50 µm dry and are measured after drying for 24 hours at 80°C, which a workshop doesn't reproduce. The manufacturer recommends 40 µm dry in cavities, below the lowest step in the datasheet, so we give no hour figure for the cavity layer.
Why these three products
They are designed to work together. The 4942 datasheet states explicitly that it is applied over Penetrant LT or over DINITROL cavity wax, so we know the layers are compatible with each other.
We chose 4010 Corroheat for the cavities rather than the softer DINITROL 1000 wax, because 4010 withstands up to 200°C short term and 160°C long term. That matters in the areas near the engine and the exhaust. The film is hard and transparent, so at a check-up we can see the metal underneath without removing the protection.
Penetrant LT and 4010 are transparent or beige-transparent. After the treatment you can see what we covered, not just that it was covered.
Why it stays waxy to the touch
The penetrant and the cavity wax are wax-based, not lacquer-based. They never harden completely, and that's a good thing: a supple film settles back into scratches and keeps protecting. The 4942 bitumen layer on the underbody is surface-dry in 6-12 hours.
How we apply them
The products only go onto a clean surface. Bitumen sprayed over rust and mud means sealed-in rust, which keeps working underneath. That's why every job starts with cleaning the underbody: a steam wash and, on used cars, dry-ice blasting.
We check the wet film thickness during application with the manufacturer's measuring comb. The comb reads the wet layer, which is why on our website we give both the wet thickness and the dry thickness from the datasheet.
Related pages
Frequently asked questions
What is DINITROL?
A range of automotive rust protection products, made by DINOL GmbH in Germany. It includes rust penetrants, underbody coatings and cavity waxes.
What's the difference between DINITROL 4942 and 4010?
4942 is the thick, bitumen-based layer that covers the exposed underbody and takes the stone chips. 4010 is a thin, transparent waxy film that we inject into the closed cavities.
How many years does a DINITROL treatment last?
The datasheets give hours in a salt spray chamber, not years on the road. How long it really lasts depends on how well the underbody was cleaned, the roads you drive on and the check-ups. We give a 2-year warranty on labour, with check-ups at 3, 6 and 11 months, included in the price.
Does it affect paint or plastic?
The 4010 datasheet says it doesn't affect paint and can be applied to rubber and plastic parts. Even so, we mask connectors, hoses and bushings, so the product only goes where it should.
Can I see the datasheets?
Yes, they're on the Technologies page, as PDFs, for all three products.