Any advocates of undercarriage rust proofing?

[XC90Mk1]

Originally Posted by TeamG

There are two factors here - quality of the system and quality of preparation. If you protect most of a piece of steel but leave one very small section exposed, this will focus corrosion at a faster rate at that spot than if you left the whole area untreated. In the 1980/90s, some bridges were constructed in North America using resin coated/plastic coated reinforcement to extend the design life (normally 120 years). Pitting corrosion was found to be pinpointed at small areas of local damage to the coatings caused by handling during construction resulting in some needing demolition between 12-16 years old, so effectively reducing the design life by a factor of 10.

If you apply such a system yourself, the worst prepared areas will typically be the least accessible dirt and water traps. Ideally remove all ancillaries such as exhaust, heat shields, wheel arch liners, brake line supporting components etc to give you the best chance of preparation. Almost impossible without a ramp.

The issue with quality is that a poor quality system will fail in localised areas such as where components rub against the system with the same result as above.

I am afraid I have to disagree here. Where you have sacrificial coatings which are damaged perhaps this is so (I can’t think of an example but I can’t rule it out).

However a small amount of similar metal exposed to elements simply will do not corrode quicker than a large expanse left out.

Crevice corrosion, pitting, interstitial boundary etc etc are not really as you are discussing.

Granted unusual things may happen direct at welded points but what you say is not going to happen in practice.

In 2006 I owned a 2003 vehicle that I painted carefully (took my time) but without any excessive prep etc (other than spraying down and brushing for 2-3 hours).

I owned that car for years without a spec of rust underneath visibly and in fact it still runs now (I don’t own it I am going by mot history checker). I had no welding required and I see no mention of corossion on mot records.

Rust treatment is an extremly interesting topic and you won’t find long term tests for home mechanic vs one of the professionals. This is in part because there won’t be as much difference as people think.

We have to be reasonable and realistic here. Doing a good job is a time consuming and dirty messy job. However it is easy to do for a home mechanic inn10-15 hours. There is no need to pay £800. The £800 may look better, and may also be slightly better but I doubt it.

Taking your example to the extreme what we are saying is that if you pay £800 and then scratch the coating (which will happen) then the vehicle will rust (a scratch exposes very small area).

Let’s keep things in perspective here, I don’t disagree that professionals have there place but I don’t really agree with the fact that it can’t be done and that small areas of metal corrode quicker than large.

Of course, I am happy to be proven otherwise but think evidence would need to be put forward to demonstrate???

[StanC]

Depending on how much you are prepared to get dirty, you could spray the underside of the car yourself. I see you are in Newcastle. Brown Brothers motor factors at Brough Park Industrial Estate sell Bodyline aerosol products, which I have found to be very good.

My 1996 960 has very little, if any, rust and I put this down to me spraying the underside and inside the box sections every three years or so since around 2008. For the underside and suspension I use Bodyline Body Scultz black bitumen spray and for the box sections I use Bodyline Cavity Wax Amber spray. The latter comes with the long nozzle tube to feed inside the box sections through the drain holes.

Stan.

[Nick04]

Originally Posted by StanC

Depending on how much you are prepared to get dirty, you could spray the underside of the car yourself. I see you are in Newcastle. Brown Brothers motor factors at Brough Park Industrial Estate sell Bodyline aerosol products, which I have found to be very good.

My 1996 960 has very little, if any, rust and I put this down to me spraying the underside and inside the box sections every three years or so since around 2008. For the underside and suspension I use Bodyline Body Scultz black bitumen spray and for the box sections I use Bodyline Cavity Wax Amber spray. The latter comes with the long nozzle tube to feed inside the box sections through the drain holes.

Stan.

Cheers Stan. Will take a look at that. As far as getting my hands dirty - not very much is the answer 😁. But I guess I could buy the products and ask someone to do it. I've seen a place in Bishop Auckland that does a proper clean and uses Waxoyl, that costs about £350-£400. There's also a place in Darlington that uses Dinitrol, but not sure about cost.

[Pidgeonpost]

Originally Posted by XC90Mk1

I am afraid I have to disagree here. Where you have sacrificial coatings which are damaged perhaps this is so (I can’t think of an example but I can’t rule it out).

However a small amount of similar metal exposed to elements simply will do not corrode quicker than a large expanse left out.

Crevice corrosion, pitting, interstitial boundary etc etc are not really as you are discussing.

Granted unusual things may happen direct at welded points but what you say is not going to happen in practice.

In 2006 I owned a 2003 vehicle that I painted carefully (took my time) but without any excessive prep etc (other than spraying down and brushing for 2-3 hours).

I owned that car for years without a spec of rust underneath visibly and in fact it still runs now (I don’t own it I am going by mot history checker). I had no welding required and I see no mention of corossion on mot records.

Rust treatment is an extremly interesting topic and you won’t find long term tests for home mechanic vs one of the professionals. This is in part because there won’t be as much difference as people think.

We have to be reasonable and realistic here. Doing a good job is a time consuming and dirty messy job. However it is easy to do for a home mechanic inn10-15 hours. There is no need to pay £800. The £800 may look better, and may also be slightly better but I doubt it.

Taking your example to the extreme what we are saying is that if you pay £800 and then scratch the coating (which will happen) then the vehicle will rust (a scratch exposes very small area).

Let’s keep things in perspective here, I don’t disagree that professionals have there place but I don’t really agree with the fact that it can’t be done and that small areas of metal corrode quicker than large.

Of course, I am happy to be proven otherwise but think evidence would need to be put forward to demonstrate???

When our V70 was serviced last week the garage (independent Volvo specialist) mentioned that there was some rust in evidence and suggested getting to grips with it rather than ignoring it. It's nearly 15 years old, so it wasn't entirely unexpected.

I've done DIY rustproofing before on our previous Land Rovers. It's a filthy job, and I can't say that I relish the idea, but neither do I relish the £600 quoted by one of the companies, or the idea of big bills after MOT failure. The summer seems a good time to do it.

I was planning on doing a thorough washing with wheel-arch covers removed, followed by a couple of days to dry, then a combination of wire or bristle brushes to clean up anything I've missed, and then apply the treatment as best I can.

Lacking a compressor, I'll have to rely on aerosol black Schulz, but possibly Waxoyl for the hollow sections.

It's a compromise, and won't be perfect of course. But I can't do a professional job at home, partly because of lack of facilities, but also I'm in my mid 70's and have had my share of grovelling under vehicles!

[Bob Meadows]

Waxoyl or similar can be diluted with clean engine oil:~
Aids the creep/flow process and spraying if used.
Bob.

[Simmy]

ancor wax. its fluid enough to find its way into crevices and easy to apply its originaly designed for boats so can handle salt water it is good practice to jet wash the surface before application now is the time to do it while the weather is fine

[Moomoo]

Originally Posted by Bob Meadows

Waxoyl or similar can be diluted with clean engine oil:~
Aids the creep/flow process and spraying if used.
Bob.

Duck oil is what I use , creeps and coagulates, used it for years , thins waxoyl a treat.👍