Morris Minor Owners Club

I'm currently in the process of degreasing, wire-brushing, rust-killing, priming, and painting Fenchurch's underside (a very long, tedious, and dirty job). She hasn't been out in the wet for at least 15 years, so the inside of her box sections etc. are all bone dry, and I want to get her fully protected now before I let her out of the garage.

I've done a fair bit of reading and although lots of people recommend Waxoyl and lots recommend Dinitrol, the consensus seems to be slightly in favour of Dinitrol due to its greater ability to penetrate into the surface of metal that's already slightly rusty (like the insides of 43 year old chassis legs). I don't think she's ever been treated with Waxoyl or anything like it before. She's just passed her MOT so she hopefully won't need any more welding for a while at least. I have a compressed air powered spraygun with a cavity nozzle on the end of a long tube and another nozzle on a short tube that appears to be for spraying outer surfaces.

As I understand it I need to spray Dinitrol 3125 into the cavities, and Dinitrol 4941 onto outside of the under-body. I want to do a decent job of it and put plenty on. My questions are: how much do I need to buy of each type, and where is the cheapest place to buy it from?

I asked Rustbuster Ltd. how much they think I'll need, and they said about two litres of 3125 and three litres of 4941. Is it just me or does that sound on the low side? I think they've based that on only spraying 4941 on the underside, rather than 4941 on top of 3125 as some people recommend (including rust.co.uk themselves in their "how to rust-proof to military standards" article). The idea of using both is that the thin 3125 soaks into all the nooks and crannies and stops the rust, and the 4941 provides a hard(ish) barrier which stops the 3125 being washed off. Would I be right in thinking 5 litres of 3125 and 3 of 4941 might be a more reasonable estimate if I put both on the underside?

I was a bit surprised when I realised just how much more expensive Dinitrol is than Waxoyl (about a tenner a litre versus about 13 quid for five litres). I can understand why Waxoyl is still more popular than Dinitrol, considering the price difference. Of course even a large quantity of Dinitrol for home application is plenty cheaper than having Waxoyl professionally applied. Since I have time, a compressor, an application gun, an inspection pit, and I don't mind getting a bit messy, it makes sense to do it myself.

They have 5Ltr tins listed on the News page http://www.rust.co.uk/news.cfm Not sure what they charge now, give them a call. Tins do come up on Ebay every now and then. Bit of a long shot but I think this chap http://cgi.ebay.co.uk/HERALD-and-VITESS ... dZViewItem
used to advertise the 5Ltr tins. Don't think he sold any and hasn't advertised them for a while but he might be worth an email....

I used to work for a Dinitrol centre, and we always used both on the floor, the cavity one first, then the thicker stuff

Dunno what others think, but I've never been particularly impressed with the longevity of Waxoyl exposed to the elements.

I think Waxoyl inside box sections and doors etc is excellent and offers first class anti-rust properties (as would any oily surface).

Perhaps if the difference between prices of the two is so great, Waxoyl is the better choice because you can afford to re-apply it regularly?

Is 5l of 3125 and 3l of 4941 about right do you think? Rustbuster do have some 5l cans of 3125 BTW, but they say they only have a few left and aren't going to make any more once those are sold. Apparently Dinitrol only sell 1l cans for DIYers and barrels for the trade, so Rustbuster had to fill the 5l cans themselves from a barrel.

Was that the ordinary Waxoyl that washes off, nebogipfel? I think Waxoyl do a thicker stuff for external use too, like the Dinitrol 4941. I definitely want to use Dinitrol 3125 in the cavities as it's supposed to be better at soaking into the surface of metal that's already a bit rusty, and there's no way I can clean the rust off the inside of the chassis rails and sills etc.

As for the underside: who knows if Dinitrol is really enough better to justify the extra cost? I don't think anyone's done any proper long-term comparative testing. Anyone want to volunteer to prepare three identical Moggies, treat one with Dinitrol, one with Waxoyl, and one with just painted metal, and report back after ten years of regular road use?

alex_holden wrote:Was that the ordinary Waxoyl that washes off, nebogipfel?

Hello Alex,

I have only ever used traditional Waxoyl as supplied in 5litre cans. Don't like the black coloured stuff - makes a horrible mess.

I wasn't aware that a thick Waxoyl had been developed?

What is the source of the info' about Dinitrol penetrating into rusted metal? I would be interested to read it.

I would have thought that Waxoyl would do that just as well?

Apparently the Waxoyl for external use is called "Hardwax Underbody Protection"? Don't know if it's the same as the black coloured stuff you've used.

The source everyone seems to quote about penetration into rusted surfaces is a Practical Classics comparative test done in 1997 (or is it 2000 - I've seen both years mentioned). I haven't read the article myself, but there's loads of forum posts on the net discussing the results. See this summary of the results for example.

I've also seen an article that claims a german product called "Michael Sander’s Corrosionsschutzfett" is the bee's knees and beat everything else hands down in a much more comprehensive test carried out by a german car magazine (they sprayed treated box sections with saltwater for a year), but you have to apply it at 90 degrees centigrade, which is a bit more trouble than I want to go to at home.

Thanks Alex, No the black I've used is just coloured waxoyl.

I was hoping the tests would be by someone more authorative than PC. Although I recently subscribed again, I take quite a bit of what they say with a large pinch of sodium chloride

My own preference for areas exposed to water spray is a good sound primer followed by a couple of coats of "Stone Chip" (U-pol Gravitex is one of the good ones) and then gloss paint. This has to be on clean rust free metal of course.

These areas can then be regularly hosed clean.

I absolutely hate underseal and schutz in all it's varieties and am convinced it does little to help and sometimes seems to promote rusting!

Undersealing in the damp or wet can trap in moisture and cause rusting. but apart from that its a Necessary evil.

I've ordered a 5 litre can of 3125 and 3 * 1 litre cans of 4941 from Rustbuster. Actually, the guy said the 5 litre can contains something that isn't actually called 3125 but is effectively the same stuff. I forget what number he said it was but he said it's the same stuff they use to treat MOD vehicles. Something to do with Dinitrol not wanting them to sell 3125 in 5 litre cans...

stevey wrote:Undersealing in the damp or wet can trap in moisture and cause rusting. but apart from that its a Necessary evil.

No, there are far better alternatives - a good sound coat of paint for one.

Underseal is just a nasty sticky black mess, sadly often used to disguise rust and bad repairs. Generally it offers little corrosion protection,dries out and flakes off and looks horrible

Just an opinion ........ I have lots of those which I share freely

If you want to protect the bottom of your freshly restored car you can do no better than paint (by all means one of the anti-rust coatings) followed by regularly applied (or at least checked) Waxoyl/Dinitrol.

In areas subject to blasting by spray and stones I would add a good quality stone chip coating as previously mentioned with a gloss paint finish applied.

Using this method you can keep the bottom of your pride and joy clean and are much more likely to spot potential problems early.

If you look at it from a historical perspective (having spent much of my working life welding rusty cars) rust became much more of a problem when the manufacturers started undersealing cars from new. Even now very old cars are often better preserved all these years on than the later stuff.

Nowadays glossy bottoms everywhere and lots of stone chip coatings but no underseal to be seen

isn't that because they are galvanised now?

You can always make your own from paraffin wax, turps and a bit of motor oil. I have had a chassis outside for months - will let you know what it looks like soon it can be as thin or thick as you like.
John

I meant a coat of underseal after a coat of paint, youd be stupid to just underseal bare metal with out protection first. i have jenolited mine (rust eater) at least 1 if not 2 coats of paint then a coat of underseal.