Tony Millward Posted October 11, 2009 Report Share Posted October 11, 2009 What we need then, is a 'flexible' medium for powder coating, I'm surprised that no-one has come up with this yet. I am aware that powder coat has to be baked after application but so do some paints and that stays fairly flexible...one for the thinkers eh?.. Tony Quote Link to post Share on other sites
Alec Pringle Posted October 11, 2009 Report Share Posted October 11, 2009 Hi Tony, there are a whole range of powders available, different specifications for different applications. Some have considerable flexibility, some have high weather resistance, or corrosion resistance, some offer higher quality surface gloss etc etc. You can't have everything in one formulation however, there's always a trade-off. I've had a fair amount of experience with using powder coating on race car applications in the past, more recently in electrical engineering applications. It is quite possible to powder coat a TR chassis and achieve an excellent result, in terms of appearance and long term performance. However, this isn't a cheap exercise. It's seriously expensive. Preparation can be costly, especially with something the size of a TR chassis. 100% degreasing is essential, along with removal of anything like welding scale or smuts.. Then it needs to be etched. Then it needs to be phosphated. That's a lot of dip'n'strip !! Only then can it be powder coated with any realistic expectation of long life. Anything less and the long term adhesion and corrosion resistance simply isn't there. Too many 'powder coated chassis' have been prepared and finished by less exhaustive methods, and the consequence is the familiar story of moisture penetration below the paint surface, corrosion continuing unseen beneath an apparently sound surface coating. The owner just doesn't realise he has a problem until disaster strikes. And of course, internal rust protection of chassis components is just as vital as with any other surface finish. At the risk of stating the obvious, satisfactory powder coating of smaller components is relatively straightforward - that's a question of physical size, preparation is less onerous and requires relatively modest size facilities. The kind of problems that Stuart has seen are the typical result of inadequate preparation and cost-cutting. The powder coating is there more for short term cosmetic and financial considerations than for long term performance. Cheers, Alec Quote Link to post Share on other sites
ianc Posted October 11, 2009 Report Share Posted October 11, 2009 I should declare that, in 1992, Colin Matthews (CTM) took the "brand new" TR4 chassis which I bought from main agent Lankester's of Kingston-upon-Thames in 1971 and incorporated every one of the mods from my 1962 Works Rally chassis so as to give me a brand new "Works" chassis. The standard of workmanship was excellent and the chassis is as tough as can be, short of adding a roll cage (which the Works Rally cars never had, of course). The metal was treated with white Corroless (gives a plastic type of finish, which resists chipping) and was Waxoyled. Apart from the dirt accumulated over the last 15 years of use, the chassis remains as good as new. Because Corroless gives a coating which is plastic, it resists the effects of stones, minor debris on the road etc. Fairly recently, in order to help trace an oil leak, I had occasion to clean a considerable area at the front of the chassis, and was delighted to find that the chassis looked like a new plate - could almost have eaten my lunch off it! I have no business connection with Colin, other than as a satisfied customer. Ian Cornish Quote Link to post Share on other sites
littlejim Posted October 12, 2009 Report Share Posted October 12, 2009 Thanks Stuart, and subsequent posters. looks like there's a bit of experience out there to draw on. Guess the galvanising is just as dependent on good preparation as the powder coating for a good result; my galvanised boat trailer is proof it won't last forever, it's rusting away in spots. All the comments give the home restorer a bit of heart. Looks like if you do the metal prep conscientiously, painting the chassis youself doesn't seem to be far behind the commercial coating processes, may be just as good or better. Except for bargain quotes it certainly will cost less. Quote Link to post Share on other sites
88V8 Posted October 12, 2009 Report Share Posted October 12, 2009 Well, I hope Johnny's powdercoat chassis passes the test of time. If it were under his control, I'm sure it would. But the precise surface prep, the choice of powder - Alec's comments - unknowns. So that's a maybe. My experience of powdercoat, not on a chassis, is that it's downright treacherous. A coherent, shiny, coat of apparently intact material that one day is disturbed and peels off in large pieces. Tapping around, one realises that areas of the remaining coat are hollow, no longer attached at all. And beneath, the water has got in through invisible cracks, and done its stuff. It's like underseal with good PR, who would entrust their chassis to underseal ? Hammerite? Well, perhaps its bad press harks back to the days when it was advertised along the lines of 'apply directly over rust', which of course one could, if one didn't mind the rust reappearing. My experience of it under cars - again, not on chassis - is that it's brittle, it chips when knocked with tools, it chips where exposed to road blast. Admittedly this is on a Landy where the wheel arches are pretty nominal, but I'm by no means alone in this experience. Perhaps it will be durable - I noticed that Simon's V8 has a Hammerite chassis from a 20 year resto - actually a 4,000 mile resto which isn't very much - so perhaps when applied over a proper primer system on a well-prepared base, it's OK. So that's a perhaps. I still come back to the point that after all the trouble of getting to a sound, prepared, bare chassis, why on earth would one not use POR15, or the 2-pack epoxy mastic I flagged up earlier, a material whose longevity and resilience is in no doubt. Why entrust all your hard work to materials whose longevity is a perhaps and a maybe? Ivor Quote Link to post Share on other sites
Tony Millward Posted October 12, 2009 Report Share Posted October 12, 2009 Robin, no matter which direction you proceed...it's all down to preparation which will make or break a good job... Tony Quote Link to post Share on other sites
RobinTR6 Posted October 14, 2009 Author Report Share Posted October 14, 2009 Robin, no matter which direction you proceed...it's all down to preparation which will make or break a good job... Tony Well thanks for the much and varied input. I'll stick with the 'chassis paint'. Having had a good look at it now inside and outside its been coated with something that appears to be galvanised anyway. The primer is removed and there is a rock hard silver coating impregnated into the metal and its not paint. Even the mig was having trouble removing it/ So I'll red oxide it a few times, and chassis black a few coats , and waxoyl the inside. Phew. After that the real graft starts, body off..... Quote Link to post Share on other sites
RogerH Posted October 14, 2009 Report Share Posted October 14, 2009 Hi Robin, don't forget to give the top of the chassis a real good seeing to as once the bosy is back on it won't be visible BUT will still be exposed to the elements. Roger Quote Link to post Share on other sites
stuart Posted October 14, 2009 Report Share Posted October 14, 2009 Well thanks for the much and varied input. I'll stick with the 'chassis paint'. Having had a good look at it now inside and outside its been coated with something that appears to be galvanised anyway. The primer is removed and there is a rock hard silver coating impregnated into the metal and its not paint. Even the mig was having trouble removing it/ So I'll red oxide it a few times, and chassis black a few coats , and waxoyl the inside. Phew. After that the real graft starts, body off..... Sounds as if its galvanized already. You can always tell as MIG welding will give off white fumes and a yellowish flame. Dont breathe them in! Stuart. Quote Link to post Share on other sites
Andy Brady Posted October 29, 2009 Report Share Posted October 29, 2009 Anyone tried that rather gucchi stuff they paint steel yacht hulls with? Quote Link to post Share on other sites
Alec Pringle Posted October 29, 2009 Report Share Posted October 29, 2009 Hi Andy, possibly not the best choice, bearing in mind that antifouling is a primary feature of below the waterline coating . . . . and it's expected to be renewed on a periodic basis. Topside or marine structure primer and paint would perhaps be a better choice . . . the kind of stuff that can survive several years on a North Sea rig should last for ever on a TR ! Cheers, Alec Quote Link to post Share on other sites
Ian Vincent Posted October 29, 2009 Report Share Posted October 29, 2009 Having in the past been a steel designer and had lots of stuff galvanised, it is very effective but it does need adequate sized drinage holes to allow the hot air inside the box sections to get out and the zinc to get in. Preparation is easy - dip it in sulphuric acid after removing all the paint and the acid acts as a flux for the zinc. Excess acid is boiled off in the galvanising bath. The only downside with galvanising is that it can warp complex fabications significantly - particularly if there are any locked in welding stresses - I have seen a fair amount of stuff scrapped because the fabrication was not suitable for galvanising - so that's the dilemma; as the man said - "Do you feel lucky". I now work in a dockyard and our standard treatment for a marine environment is etch prime followed by two pack epoxy. Alternatively, for the outside of the chassis and all suspension components zinc metal spraying followed by two pack or hammerite or POR15 will give you a paint treatment that would outlast anyone reading this forum - the metal spraying leaves a fabulously rough surface for the paint to bind on to and any scratches in the paint will remain just that because the zinc will provide galvanic protection and stop rust creeping underneath the surface - which is what can happen with powder coating. Rgds Ian Quote Link to post Share on other sites
Ian Vincent Posted October 29, 2009 Report Share Posted October 29, 2009 Robin, I just re-read your post and in response to the bit about it possibly being galvanised be aware that painting fresh galvanising is tricky. And remember that in removing the existing paint you may polish or abrade away the top layer of your old galvanising to expose fresh zinc. Back in my steel designing days we either left galvanised structures exposed to the elements to weather for 6 months before painting them or we treated them with T-Wash. T-Wash is phosphoric acid based (I think), and turns the nice shiny galvanising black when properly applied. I am sure you can still buy it - try googling it. Without this you run the risk of the sort of leprous effect that galvanised steel lamp posts sometimes exhibit when the paint peels off in sheets. Rgds Ian Quote Link to post Share on other sites
BrianC Posted October 30, 2009 Report Share Posted October 30, 2009 I was told that galvanising increases the weight considerably and also makes any subsequent welding extremely difficult. Does zinc spraying have similar complications? Quote Link to post Share on other sites
Ian Vincent Posted October 30, 2009 Report Share Posted October 30, 2009 I was told that galvanising increases the weight considerably and also makes any subsequent welding extremely difficult. Does zinc spraying have similar complications? Brian, The problem with galvanising hollow sections is that no matter how careful the galvaniser is, you are likely to end up with a fair amount of zinc trapped inside the sections - hence you can add quite a lot of weight. As far as welding is concerned, galvanising is not just on th surface of your steel. Yes there is a top shiny layer of pure zinc but beneath that there are two layers of zinc iron alloy. Both of these alloy layers are harder than either the base steel or the outer zinc coat which can make them tricky to remove. Welding onto zinc can be done and when I worked on site, we did quite a bit of it, use the right sort of rod and give the welder a pint of milk to drink before he starts. Nowadays you can't get away with that because the long term health effects of ingesting quantities of metal vapour are better understood - they poison you. Also if you aren't skilled it is easy to get a porous weld which isn't very strong. Metal spraying is easier to grind off than galvanising but is just as bad a galvanising for creating zinc vapour. In terms of weight, because metal spraying is an external process you don't have the issue of filling the inside with lumps of zinc and you don't have the possible distortion risk - crudely described, its just zinc wire being shredded in front of a blowtorch. As has already been said, you can spray the inside of the chassis with dinitrol. Rgds Ian Quote Link to post Share on other sites
Andy Brady Posted October 30, 2009 Report Share Posted October 30, 2009 Hi Andy, possibly not the best choice, bearing in mind that antifouling is a primary feature of below the waterline coating . . . . and it's expected to be renewed on a periodic basis. Topside or marine structure primer and paint would perhaps be a better choice . . . the kind of stuff that can survive several years on a North Sea rig should last for ever on a TR ! Cheers, Alec Oops, That's what I meant! Yes, I was thinking along the lines of INternational Danboline bilge paint, purpose made to resists oil, fuel and saltwater. Quote Link to post Share on other sites
Alec Pringle Posted October 30, 2009 Report Share Posted October 30, 2009 Hi Andy, Danboline and similar ought to be very effective, as always assuming correct preparation and priming. How resistant it is to impact damage, as in flying stones and suchlike, I don't know - but it's hellish tough stuff to strip off ! It's also jolly expensive, unless you have access to a commercial supply. Cheers, Alec Quote Link to post Share on other sites
Anschutz Posted October 30, 2009 Report Share Posted October 30, 2009 Just thought I would add my experience with powder coating, chassis and body were both powder coated after shotblasting in 1979 after rebuild. 6 is now at TRGB for bare metal respray. I stripped all the paint off the outer panels (not P Coated) but the paint stripper would not touch the powder coated engine bay so they recommended that the engine bay and other P Coated parts be blasted to remove said powder C as they didnt like it! There wasn't any rust on the powder coated parts (Car also waxoiled) so I have no complaints about Powder coating and hopefully car will last as long again which should see my TRing days out. Quote Link to post Share on other sites
Alec Pringle Posted October 30, 2009 Report Share Posted October 30, 2009 Excellent. After 30 years of wear and tear, that certainly proves that the chaps who powder coated your car knew exactly what they were doing, and how to do it properly. If they're still around, perhaps you ought to let them know what a good job they did ! Cheers, Alec Quote Link to post Share on other sites
88V8 Posted October 31, 2009 Report Share Posted October 31, 2009 The problem with galvanising hollow sections is that no matter how careful the galvaniser is, you are likely to end up with a fair amount of zinc trapped inside the sections - hence you can add quite a lot of weight. Landrover chassis used to be galvanised, but they found there was typically 60lbs of pooled zinc lying in the chassis afterwards, in addition to the actual coating on the chassis. Also, there is a hot air explosion when the chassis enters the molten zinc, so there have to be big holes in any box members for the expanding air to escape, otherwise the chassis distorts. Hence the huge holes in early Landy chassis. Btw, there's a galvanised TR6 chassis on eBay right now, so it is possible. Fresh galvanise can be painted with calcium plumbate primer. Although lead-based, it's still available. Ivor Quote Link to post Share on other sites
Mychael Posted November 25, 2009 Report Share Posted November 25, 2009 (edited) I just did a forum search for opinions about powder coating and now don't know what to do. I'd mentioned on another posting that I've purchased a restored chassis, which has been jigged, re-enforced, flushed internally AND powder coated. What should I do ?? Incur a lot more expense on top of my original purchase and get the chassis fully stripped again then painted or leave it as is. Mychael Edited November 25, 2009 by Mychael Quote Link to post Share on other sites
RogerH Posted November 25, 2009 Report Share Posted November 25, 2009 Hi Mychael, the concern with powder coating is if it cracks/splits and is then imersed in water (typical UK) then water may get under the otherwise perfect coating and proceed to rust away quite merrily. I would imagine in Oz that rain is not your biggest issue generally speaking. I would stick with what you have and think about it in 10 - 15 years time. Roger Quote Link to post Share on other sites
Mychael Posted November 26, 2009 Report Share Posted November 26, 2009 Hi Mychael, the concern with powder coating is if it cracks/splits and is then imersed in water (typical UK) then water may get under the otherwise perfect coating and proceed to rust away quite merrily. I would imagine in Oz that rain is not your biggest issue generally speaking. I would stick with what you have and think about it in 10 - 15 years time. Roger Thanks Roger, We don't salt our roads which is a big plus. I've sent an email to the shop that did the chassis and asked him (without prejudice)( don't want him thinking I'm trying to make him responsible) exactly what he did for preparation prior to powder coating. Hopefully he'll give me an honest answer. Also asked my mate who is a retired engineer and paint engineer from GMH his opinion on powder coating he has no issue with it, ran it past the guy who did my bodywork last time and will be doing the other chassis mods for me. As he will need to remove portions of the powder coating anyway to do the extra welding his thought is to wait and see what he finds but generally speaking he also has not heard of any issues. Having said all that I really need to get it right now before I commence fitting a restored shell etc etc. Mychael Quote Link to post Share on other sites
Alec Pringle Posted November 26, 2009 Report Share Posted November 26, 2009 Hi Mychael, old coarse technique . . . . 1" cold chisel at 30 degrees to the painted surface. 2lb hammer. Apply the latter to the former ! If it chips off a decent size chunk of powder coat, the stuff is rubbish, get rid of it. If it makes little more than a scratch or a chip, stop worrying about it. That simple. At the risk of stating the obvious, do the experiment at a point where your man will be welding, you won't miss the chip then ! Cheers, Alec Quote Link to post Share on other sites
Mychael Posted November 26, 2009 Report Share Posted November 26, 2009 Hi Mychael, old coarse technique . . . . 1" cold chisel at 30 degrees to the painted surface. 2lb hammer. Apply the latter to the former ! If it chips off a decent size chunk of powder coat, the stuff is rubbish, get rid of it. If it makes little more than a scratch or a chip, stop worrying about it. That simple. At the risk of stating the obvious, do the experiment at a point where your man will be welding, you won't miss the chip then ! Cheers, Alec Thanks Alec, Sounds like a good place to start. Mychael Quote Link to post Share on other sites
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