bazz54

Ok, so it's interesting to look at this http://www.bilthamber.com/media/downloads/PG-BH13-001.pdf which may have been posted on the forum previously. Of course, the obvious limitation of this test study is that they applied the "underbody treatment" directly to bare steel and leave you to assume that the results would still be valid if they'd put it on painted steel. But then, perhaps they would have found that when put down on top of a good paint system, the underbody treatment adds little additional protection? The test do prove, very convincingly, that without paint, the underbody treatments all allow rusting under the test condition being used.

It would be really interesting to know the name of the product they are using. Don't get me wrong about putting additional "rust protection" on your car, I'm all for that, but I'm definitely not a fan of the black, soft, goo that people have traditionally referred to as "underseal". I did my rear sub-frame and petrol tank (using zinc phosphate primer and then a professional metal cladding top coat) back in April, and judging by the thread which has started about front sub-frames, looks as though I need to get the brushes out again

Well that is interesting, because as I've said on here before, I stopped using "underseal" years ago. During the 60's and 70's when cars were real rot boxes, loads of firms started up to do underseal and that was usually black sticky stuff that didn't seem much different from tar. When new it was really soft but it progressively dried out and after a length of time it was often possible to pull it off in great patches and pretty often there was rust occurring underneath. So the questions seemed to be; (i) just how effective is this stuff at preventing corrosion (ii) how good is at at forming an adhesive bond with the paint layer and (iii) can it actually make things worse, if only by hiding rust? Waxoil came along later and seemed to be better (?), but at the same time, paint technology improved enormously, so body rot on cars now takes far longer to get started than before. So if the stuff these guys are using looks like hard paint, then maybe it is hard paint, but one that's formulated to be a thick tough barrier and resistant to impact, which I'd guess are the key properties of an "underseal". But I think I'm right in saying that you can still go down the high street or go on-line and buy tins of black tarry stuff (just like 40 years ago), labelled "underseal" and is just fine..... for a car you're going to sell next week. B

When you ask for someone doing "underside treatment", are you including the pre-cleaning and application of either a paint or an anti-rust treatment prior to the underseal? This place (near Aylesbury) has an interesting website http://www.thepaintshoppros.co.uk/car-underbody-rust-protection-service/ but I have no experience of using them. They apply what looks like a phosphate conversion treatment before the underseal. One point to note is that they reckon that their whole process needs re-doing every few years. Personally, I definitely want some good rust-inhibiting primer paint going down before underseal and think that any other approach is a mistake. Underseal hides what's going on beneath it and I don't generally use it these days. B

Those comments are absolutely true, and if you can get something in to a workshop and have easy access to all the surfaces, fine. But that strategy is harder to live up to if you're dealing with the underside of a 15 year old car, and even more so if it's just sitting on axle stands. Under those circumstances you're probably going end up with 4 kinds of surface; i) areas in original condition and still good ii) areas which rusted and you were able to do a really good job or brushing or grinding back iii) areas which rusted, but were hard to get at and you did "the best you could"; there may be some traces of rust left. iv) areas so badly rusted, welding is required So you have to decide are you going to re-paint each of those areas in different ways, or adopt a compromise solution to cover everything. I think the outcome here is that there is no one perfect answer and ultimately, people will tend to go with the approach they believe has previously worked well for themselves or their friends. That said, I suspect that there are some totally over-rated products out there, and some of them have managed to stay around for a long time and some have big price tickets!

Yeah, but the problem is that the term "red oxide" now refers only to the colour of the paint and gives you no info whatsoever about what kind of paint it is. Originally, red oxide referred to paint containing red lead oxide, which was a good corrosion inhibitor, but is now banned. Buying red oxide paint now is just a lottery, unless you get some tech info from the supplier.

Subsequent to my OP, I did a bit of digging for info and found that the two paints I quite like these days (Hammerite's Beat Rust and Screwfix's Red Oxide) turn out to both be zinc phosphate paints. The Screwfix stuff is actually made by Johnstones, who are a top British company and part of the worldwide PPG group, and as well as making domestic paints, they do paints for little things like oil rigs, bridges etc. I was lucky to spot a 5L tin of Johnstones industrial "fast drying zinc phosphate" going very cheap on eBay and have just used that for the first time today, and not surprisingly, it appeared in all respects to be exactly like the Screwfix red oxide. The things I like about this stuff are (i) it is a very good "wetting" paint that seems to adsorb on to surfaces really well, doesn't need much brushing in and (ii) even without a top coat, seems quite good are arresting/preventing rust. The ebay seller also had 5L of Johnstones industrial semi-gloss, high-build top coat, so that's going on next.

I'm coming up on 11 years now and very pleased that I bought it, even though I didn't originally know about the G7 pre-facelift engine issue it, but so far, that problem hasn't shown on my car.

This issue with subframes seems vaguely reminiscent of the problem with the original mini years ago. I never owned one, but always had the impression that the rest of the car could be great but the subframes completely gone. I've just bought 5L of Johnstone's zinc phosphate primer and 5 L of their semi-gloss over-coat (well below list price on ebay) and need to make a start on both cars ASAP.

One of the other known issues with chloride is that once it is on, it is bloody difficult to wash it off completely (even though you won't be able to see it). Consequently there are products on the market specifically claiming to help remove it, like this stuff from the Rustbuster paint folks http://www.rust.co.uk/4-salt-removal/t16/ I'm not recommending this particular product, simple because I've never tried it. But, I will be doing some painting on the underside of my Gen7 this spring and even after using lots of water to clean it, I probably will use this or something similar before slapping the paint on.

Road salt (sodium chloride) greatly accelerates corrosion simply because it is a source of the chloride ion. If you looked at any text book on corrosion it would tell you that chloride is just about the worst contaminant in the everyday world for initiating/maintaining rust. I used to work in corrosion testing and I've seen corrosion test specimens where you could see finger prints (caused by the salt in sweat) on their surfaces even after they been in hot gases for thousands of hours. Remember also that kitchen washing up liquid is loaded with salt and should be kept well away from cars.

Are you going to strip the whole wheel or just do the bad bits? If the latter, what I have used in past are the small (cheap) tins of Humbrol enamel paint intended for model makers; I think they do a number of different silvers of different shades.

No one has mentioned it, but it is important with aluminium to start off with primer coat using a paint intended for aluminium. The last time I painted aluminium I think I used an aerosol etch primer made by Clostermann and that seems to have lasted.

The original red oxide paints contained lead, but have now been very much restricted (banned?), so the term "red oxide" now mainly refers to the colour of the paint. Though it's generally accepted that "Red Oxide" paints are rust/corrosion resistant, any two of them could fairly different. All that said, Screwfix do a a very inexpensive Red Oxide, which brushes on and takes to surfaces very well (some paints seem "stodgy" by comparison), and I've not used it on a car, but it does seem to have done well on other stuff that gets left outside.

Picking up from the thread in the Gen7 sub-forum which suggests that corrosion on 7's (rear sub-frames and petrol tanks) is now becoming an issue, I'm curious about what people currently think are the best paints for dealing with such problems. A couple of people on that thread say they'll be using Hammerite, and in the past I would have agreed with them; Hammerite used to be the dog's danglies. But lots of paints have had their formulations changed in recent years to suit health/safety/environment requirements, and in the case of Hammerite's "direct to metal paint", I'm not sure it's as good as it used to be. I recall seeing comments on other car forums that the current formulation is hard/brittle and does not do well where the component is subject to flexing or stone impact(?). I do have quite a good opinion of Hammerite's "Rust Beater", which I think is a completely different product to the direct to metal stuff. As my 7 is coming up on 14 years old , I probably need to take a look at the chassis when the weather gets better. B

I just looked at that site and got up the details for my other car which is a Rover 600. It said exactly the same thing - most failures on lights/electrical and then on suspension. On the R600 owners forum, the number one risk of MoT fail is always regarded as the handbrake. As yet, my Gen7 has never failed. As suggested above, that data might tell you more about owners than cars.

When it comes to the compatibility of rubbers with fuels, intuition is not always a good guide. Who would have expected that too much bio-diesel in diesel or ethanol in petrol in ordinary fuel could have the really bad effects on some rubbers which it has? Seeing as the hose will not be permanently wetted, I suspect you could get away with it. Personally, I'd rather have the right material; is the issue cost or availability?

Agreed; maybe OK for cars on their last legs...or about to be sold

Yep! If it is not leaking, I bet it is slowly taking more as it purges out air. As for boiling points above 120'C, well all conventional coolants are 50% water, so how much higher than 120 can the boiling point go, and how often would you ever experience that? I've never changed the thermostat in a Gen7, but on every other car I've ever worked on the stats are usually begin to open around 90'C. So short of a track day, or being stuck in traffic on a really hot summer day, I would have thought 120 was OK ?

There can be significant differences between types of coolant, but they would not account for coolant loss. Up until a few years ago, pretty much all coolant antifreeze was ethylene glycol with certain corrosion inhibitors -really important for aluminium engines like ours. Then some new mixtures came out with better corrosion resistance (supposedly!!!). To id the two types, the companies brought in colour-code systems, but different manufacturers used different colours. The simplest thing to do is stick with toyota coolant of the same colour as was in originally; it has been suggested that mixing the two may cause corrosion problems. But if you are losing it, there has to be a leak somewhere.