Painting Mild Steel Exhausts

[Bonzodog]

I am about to fit a new mild steel exhaust system to my Conquest and would like to put something on it to stop it rusting. Yes, I know they mostly rust from the inside but my concern is chiefly cosmetic. Any suggestions?

[Fossil]

There are many high temperature sprayable exhaust finishes available from many automobile parts and accessory suppliers such as Halfords, Frost and so on, in a wide range of colours. I suggest that you use the power of Google to narrow your choice of colour and source.

From personal experience the finishes last best if they are done on clean metal with proper surface preparation to remove dust, oil and so on, and then allowed to cure for as long as can be done without the heat from the engine which completes the process, before assembly. Unfortunately assembly entails much handling which can spoil the coating, especially if the fit is not precisely correct and requires much manipulation, and the only way to find out if this is the case is to do it, or get a professional exhaust fitter to do it, before applying the finish.

Then once the engine has been run and the paint cured completely the finish should last reasonably well, best perhaps on the hottest parts and least well on the areas most expose to road debris. My advice to get the longest life from a mild steel exhaust and the coating, FWIW, would be to use it only for longer runs to get the entire system hot enough to prevent condensation from causing corrosion, and to use the car only in dry weather. I've seen mild steel silencer end plates rot out in just a few months of short run winter use. But in the right conditions they can last for years

[Phillmore]

Where did you get your exhaust system from BD? I need a rear section for one of my Conquests.

[Ian Hastings]

Allegedly a well known car manufacturer many years ago would paint the exhausts with cooking oil or similar then let the heat of the exhaust convert the cooking oil into the black burnt glazed finish that would adorn your roasting trays used for the Sunday roast.

Apparently it worked very well as a rust proofer but probably a bit smokey for a while.

[Bonzodog]

Thanks for the replies. I have seen reports of good results being achieved with BBQ paint (very good heat resistance obviously and good at covering light rust).

Phillmore - my system came from John Nash (Daimler Enthusiasts' Club). I bought it a while ago so can't quote a current price but I can say it is so beautifully welded it seems a shame to fit it.

I did pick up a new old stock (ex DLOC stores in fact) system at Beaulieu a few years ago and interestingly it is noticeably much heavier than any other system I have handled.

[Fossil]

Richard

Yes, I think the original systems were made of substantially heavier gauge metal and were probably fairly straightforward to assemble, being much more accurately made. I have a couple of heavy old mild steel Century silencers somewhere in the garage, but I recall some replacement mild steel systems being difficult if not almost impossible to fit with regard to alignment with the chassis and attachment points when assembled. And they tended to have a relatively short lifespan.

To eliminate these recurrent problems I eventually took the stainless steel route and I still remember that putting that Century system on was a pleasure, it was so well aligned. I think that one was from PD Gough. It has truly been fit and forget; the only problem I've had has been loosening of the rear manifold to downpipe flange bolts. they are so difficult to get at. This was solved by using new shakeproof washers, and I also made up an additional bracket to support the downpipe, attached to the two bottom bellhousing to engine backplate bolts, which I hope will reduce the stress on the manifold to downpipe flanges.

Regards

Geoff