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Painting the frame
The paintwork on the frame of my '82 RS is in a right state. As I'm going to give it a major overhaul, g'box bearings, timing chain & tensioner, big-ends & mains, valve seats, new discs and brake lines, and complete exhaust system, I'm thinking I might as well paint the brute as well. (The last time I added all that up it came to about a grand, I stopped counting after that.) Anyway, what paint / primer should I use, both for the frame and for the alloy forks? Also, does anybody know if BMW used any fancy steel for the frame: the reason I ask is that because they use high tensile steel in some aircraft you can't use things like Kurust, Rust Eater & Jenolite to cure surface rust as the phosphate compounds formed have the effect of locally hardening the steel, a Bad Thing apparently. So it has to be removed mechanically, which I assume means it has to be scraped/emery clothed/filed off. As I'll have plenty of other work to be getting on with Jenolite etc. seems to be the quickest way by far, I don't need perfection, so the question is, can anyone tell me if it's OK to use it?
Thanks to everybody for their responses to my previous questions, they were all most helpful. John ------------------ Johnefyn |
I'd go for several coats of Hammerite, but it takes time to cure between coats, and it isn't cheap. It supposedly doesn't need a primer, but I'd go for a zinc or self-etch primer. Of course that would be a problem if the steel is HT, and what you've heard about HT is true. I think it may be; from memory, engineering grade HT bolts can't be exposed to acids, but that's because the stressed threads might fail. I really doubt this would be a problem on a frame, though. What would happen with combustion acids in HT frames that carry oil?
The obvious and best alternative (although expensive) if you have a totally dismantled frame would be a good bead blasting and powder coating. Considering your costs already, I'd paint it myself if I were you. But then, why ruin the ship for want of a bit of tar (or paint)? Having restored a couple of old Triumph sports cars, once rust manifests itself it has to be totally removed and properly sealed to stand a chance of stopping it from returning. Good luck! Stig |
As Stig proposed, I completely stripped, sand blasted and powder coated my Tenere and it turned out great. I highly recommend it but keep in mind it’s limitations: Powder coating will do a great job protecting the metal but it doesn’t treat rust like Hammerite or POR, it will just cover the rust badly and soon the rusty area will chips off. Also, as far as I know, retouching powder coating isn’t possible, you’ll either have to redo the entire frame or touch it up with regular paint.
------------------ A.B. OasisPhoto.com – Images from the Magical Sahara. ShortWheelbase.com – Jeep preparations. Coordinates Converter – Lat/Long <-> UTM Conversion Tool. |
Whatever finish you're going to apply, I would thoroughly de-grease it, get it sand-blasted and _immediately_ get some primer on, preferably an etching variety.
Having said that, the last bike frame I did was a Gilera 50cc moped about 25 years ago, so I shouldn't take my advice a too well informed. I do know though that freshly-cleaned steel will start to corrode almost immediately, so the quicker it's covered the better. |
Thank you both, i.e. LordStig and A.B.
Regarding doing a proper job of the repainting, that is, stripping the frame to bare metal; I must admit that that is the only way to do a proper job. But, the thing is, I'm worried that with a job this big (remember I'll be doing a lot of mechanical work as well) then there's a danger that it just won't get finished. I started a complete overhaul of a 1934 PA MG in 1966, did 95% of the work, left home to go to college and I never touched it since. So the possibility of losing interest before finishing is a real threat. As for Hammerite, I don't trust that as it seems to chip very easily, more so if you put on a lot of coats. (If I remember, it's ok to recoat within a few hours of the first one drying, otherwise you have to leave it a long time to allow it to harden fully before further coats.) Anyway, from what you say, I might go ahead and give it the Jenolite (or whatever) treatment. A.B.- the only thing I can remember about plastic/powder coating is that it does look good when new, but bloody awful when corrosion sets in after slight damage, so I do have reservations about that. Er, what's POR? Thanks, both. John ------------------ Johnefyn |
IanC- Just seen your reply-I must have got it just as I posted my replies to LordStig and A.B
Yes, I agree absolutely with what you say about getting the bare metal coated as quickly as possible. A monumental mason who had a small sandblasting cubicle did some work for me a few years ago, (he used to make pictures on gravestones, I think he used some form of stencil and used the sand blasting as a sort of airbrush) He accidentally got one end of the part wet and although he wiped it clean immediately I had rust coming through on that end within a few weeks. So with the metal being chemically clean it seems to be eager to pick up any contaminant. The job was a freebie-no guarantee! Cheers, John ------------------ Johnefyn |
John
I'm not very keen on Hammerite myself. Like you say, the re-coating process is rather odd, and they don't recommend a primer. It always seems to me a bit thin in the "dimples". I'm sure in Wales (south anyway) you are spoilt for choice of people who have the gear to quickly and thoroughly do any sand-blasting. If I'd gone to so much trouble as to have everything stripped off the frame, I wouldn't skimp on the re-painting! You'll be p****d off if it starts rusting next winter! I'm no expert, but I have a feeling 2-pack epoxy may be the way to go? Regarding "losing interest", the Gilera I mentioned ended up with a very nice frame. Unfortunately, nothing was even attached to it (at least by me)! ------------------ www.aslc43.dsl.pipex.com |
Ian,
I heard once that most "ordinary" paints & enamels are porous to a greater or lesser extent, hence their imperfect protection against corrosion. As far as I can tell, Hammerite does give protection irrespective of whether any corrosion has been removed prior to application, as long as it isn't damaged or chipped, and I've attributed this to Hammerite not being porous. Perhaps somebody can tell me if I'm talking bollocks. And I do agree that it does seem thin in the dimples, must be a weak point, surely. I used to work with BT (British Telecom) and the underground cable jointers used two-part epoxy resin to encapsulate a completed joint, apparently this was absolutely impervious and non-porous, so perhaps two-pack really is the way to go. Nay, nay, (and thrice nay) I am NOT stripping the frame clean,(I mean I'm not taking the bits/wiring/swing arm/forks): this will be at best an imperfect quickie to stop the thing rusting away, even though I may feel guilty for ever more for having done half a job! Thanks Ian, John ------------------ Johnefyn [This message has been edited by John Roberts (edited 27 April 2004).] |
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------------------ A.B. OasisPhoto.com – Images from the Magical Sahara. ShortWheelbase.com – Jeep preparations. Coordinates Converter – Lat/Long <-> UTM Conversion Tool. [This message has been edited by A.B. (edited 27 April 2004).] |
Hi Ahmed
I've just had a look at your gallery: amazing! Go take a look, everyone, see it at OasisPhoto.com. (see A.B.'s reply above.) Oh, and thanks for being so frank about not having yet completed the repainting project! Best wishes, John ------------------ Johnefyn |
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