Rust prevention.....

Scania

Scania

Scania

Caporegime
Joined
25 Nov 2004
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On the road....
Having just had my 16 year old Volvo MOT’d the tester advised that I got some rust prevention treatment applied to the underside of the car,although this wasn’t listed as an advisory as such, something akin to oil spraying, just wondering if there’s a better option other than just using old oil (as I have done so in the past albeit on a different car) , he said there’s nothing worse than surface corrosion but treatment now will significantly prolong the life of the old tank.

Any recommendations appreciated. :)
 
I've been thinking about doing something like this for a while, my Volvo is only 7 years old and actually really pretty good underneath and id like to keep it that way.
 
Thebug said:
It’s probably waxoyl he was on about

https://www.hammerite.co.uk/product/waxoyl/
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Actually, he specifically warned against Waxoyl, I immediately suggested using it and he advised against as over time water gets behind the waxoyl and rust starts to form unseen, by the time it's an issue, it's too late. I had an old '84 XR3i that had been wayoyled from new - which was such a selling point back in the day - and it passed every MOT with no corrosion issues, then came the day it turned out it was actually riddled underneath , neatly hidded by the layers of black stuff....

@VaderDSL I've seen that stuff used on commercials, swaying towards this option, thanks.
 
I used Dinitrol 4941 on my 850s wheel arches and boot floor plan. Preventative more than anything, but its stood up well for the year since I've done it, with 5-6 pressure washes/APC applications. Only used the one can, so fairly economical too.

BH is also great, and has added benefit of having clear options.
 
I found the Bilt Hamber Dynax stuff great when I did my mx5. The UB brushed on nice and easy without any real mess. The S-50 for inside the box sections come with a 360° spray Lance and coats inside box sections very well. I had before and after pictures using an endoscope and everywhere was fully coated. I did my 5 in 2016 and it's still going strong with the current owner and not showing any signs of rust (which for a MK2 is very rare, although it was a fresh import in 2012)

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If you want something you can just spray/brush on quickly on vulnerable spots: ACF-50 or XCP rust blocker. XCP lasts longer but is more expensive.

Apply 1-2 times a year and that should stop it, keeps salt out too. They take a very long time to wash off (as you'll find out if you get them on your hands :p). You can actually do the bodywork with ACF50 and water/mud won't stick to it for ages lol

For the more perminent coatings I think they are designed to be put on before rust appears. Or after it's been 100% dried and removed. Otherwise it can make it worse. So don't do it at this time of year.
 
Last edited:
I work in the Oil Industry and the guys use Rust Veto to protect subsea equipment that has been shot blasted.
Equipment can be stored outside for years and still look as if they had been recently shot blasted.
All of them use that on their cars.
 
dale1uk said:
I found the Bilt Hamber Dynax stuff great when I did my mx5. The UB brushed on nice and easy without any real mess. The S-50 for inside the box sections come with a 360° spray Lance and coats inside box sections very well. I had before and after pictures using an endoscope and everywhere was fully coated. I did my 5 in 2016 and it's still going strong with the current owner and not showing any signs of rust (which for a MK2 is very rare, although it was a fresh import in 2012)
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What's with the metal plates on the chassis rails?
 
Agent_Smith357 said:
What's with the metal plates on the chassis rails?
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They are P5 frame rails and are designed to increase the rigidity of the shell. They also help protect the rails from damage from speed bumps or from jacking.

If I'm honest they didn't make a huge noticeable difference, mk1s are supposed to benefit more. The added protection to the rails made them worth it though.
 
sand to bare metal or get loose rust off, use rust converter then epoxy primer and then use stonechip on top. can pain on top of stone chip if you want it to look better.
 
nudging this thread -
rust I'd treated on my bike frame is peaking through after 6 months with loctite 7500 rust 'convertor', so I'm a bit p**** off.

Dinitrol
Cookeh said:
I used Dinitrol 4941
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was considering this as a base coat for my re-work, remembering thread, but it seems it is an oil, so can't be painted on top

After watching
Best Rust Converter? POR-15, Eastwood, Rust-oleum Rust Reformer, Gempler's
I'm tempted to try por-15 or rustoleum rust reformer - any lived experiences ?
 
ACF-50 is brilliant - very easy to apply, actually inhibits existing corrosion and prevents new - but big caveat that it only lasts a few months before you need to reapply and can be a bit messy if you spray it around ad lib. Unlike a lot of products it is the real deal while its protection lasts - but the last time I only got about 8 months out of it before new corrosion started appearing.

Looking at using a mixture of Bilt Hamber (to arrest existing corrosion) and Dinitrol (for areas I can't easily get to) on the pickup at the moment :s it was doing great up until all the road salting at the start of 2021 and then again the last few weeks when they've gone nuts with it around here despite the night time temperatures rarely getting below 7-8C. Not decided what to go over it with (before the Dinitrol) once the surface it prepared to give some longer term protection though.
 
Rroff said:
it was doing great up until all the road salting at the start of 2021 and then again the last few weeks when they've gone nuts with it around here
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yes - that's like cambridge - I wonder if I should wash both underbody of car and bike more regularly ... well, tbh last time I used the attachment on Karcher was several years ago.

and vision of below honda chassis sticks in my mind.
jpaul said:
2021 Honda Accord Hybrid | Ignore the Soundtrack

video shows their ecvt working, but, the issue of modern day corrosion of cars in mid west usa is astounding .
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I wish I had before pictures - it was close to new looking on the chassis rails and just a light bit of corrosion on the exhaust, rear axel diff and some cross members - probably less than 6 weeks of salt spray leaving the vehicle after a run looking like a zebra and you'd think it had been rusting for 10 years :(
 
older article on salt corrosion - maybe I should make first ever trip in my life to an automatic car wash that does the chassis.

https://www.inquirer.com/philly/bus...to_wash_cars_often__fight_salt_corrosion.html

Determining that the problem was not the result of a manufacturing or design defect, NHTSA blamed rust caused by road salt and a lack of washing. It urged people in 20 cold-weather states - including Pennsylvania, New Jersey and Delaware - as well as Washington, D.C., to have their car and truck undercarriages washed several times during and after the winter, and to get their brake lines inspected for rust and replaced if necessary.
 
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