MOT Rust standards

PC Paul ( snipped-for-privacy@home.com) gurgled happily, sounding much like they were saying :

If it's just surface corrosion, don't worry about it. The tester will only care if it's affecting the function - in which case, YOU ought to care, too... After all, the tester won't be in the care if something breaks...

The above advice is good. The only thing to watch out for is sharp edges. A valid reason for failure is "A sharp edge or projection, caused by corrosion or damage, which renders the vehicle dangerous to other road users, including pedestrians" (taken from the bottom link above)

Ian

Some rust appears less innocuous than it is. The best thing to do is to hit it with a welding hammer and see if it goes through. The tester is likely to do this with bits he may be suspicious about.

Re keeping underneath rust at bay, an infallible method is to spray it with old engine oil. Rust definitely will give in to this. The downsides to this treatment are (a) you need to keep doing it as often as is necessary - say once a year, depending - and (b) it's not very good for rubber parts in suspension joints and so forth. But you can keep it off these with care, and (c) it makes the underneath dirty - but do you care?

Some others may say that you can achieve the same results with Waxoyl, but I never have, and old engine oil is free. You just need something to be able to spray it on with.

If you try using stop-rust stuff and/or underseal you're wasting your money. In my experience, stop-rust stuff doesn't stop rust, and underseal simply hides rust that continues to work underneath. However, if you look at a machine such as an agricultural machine of any age you'll see that the bits that never rust are around the bearings where oil/grease has seeped over. OK, it's not pretty and you wouldn't do this on parts you can see, but it's pretty effective. The general idea is to get oil all around the metal and hope dust sticks to it and accumulates a bit to provide a lovely rust protective coat about 1/8 inch thick.

Rob Graham

Useless. First time out in the wet and it's gone.

Steve

No!

the tester is only allowed to hit the areas with his trusty C.A.T. " hammer " - Corrosion Assement Tool or commonly known as a toffee hammer only this one has a plastic head with an aluminium handle which you can use for " light " scraping as this is the only tool authorised by VOSA.

Cor!!! I could make a hole in an a new car with a chipping hammer :O)

Probably less dangerous than the fact they'd have to be well under the car before they could get anywhere near it, but point taken lol.

Doesn't look like it's bad enough to be a problem, this year at least. And for a K reg with 146K on it, there may not be *too* many years left - although Mazda do seem to have quite a good reputation in that area. Never had one before...

Cheers for all the advice

OP

I assume this is a preventative method only? What would you recommend doing to the rust that already exists on the car...like in the OP question? (helps me too :o) )

That's better - Well done.

Steve

;o)

Whatever stage the rust has got to the oil will stop it getting worse. The rust won't continue if it's in a skin of oil. And, as I said, try to get a layer of dirt on the oil and put more oil on so that you have this protective layer of dirt mixed with oil.

If the rust is already serious enough then it'll need welding. But if it's not got to that stage then oil will keep it OK.

Rob