To powder coat or not?
Discussion
Hi all
I am in the process of a body off rebuild of the Griff and i am now at the stage to send the chassis for blasting.
DO I: (a) just have it hot zinc sprayed and primed and paint by hand. or
(b) Hot zinc, primed, and powder coated.
I know there is some pros and cons as to powder coat. The other option is to paint after it has been zinc spayed and primed. I do feel that the powder processes have improved over the last few years (especialy compared to TVRs efforts).
I have until thursday to decide and i would like not to have to do this job twice or have a finish i would no be happy with.
Thanks in advance Mark
I am in the process of a body off rebuild of the Griff and i am now at the stage to send the chassis for blasting.
DO I: (a) just have it hot zinc sprayed and primed and paint by hand. or
(b) Hot zinc, primed, and powder coated.
I know there is some pros and cons as to powder coat. The other option is to paint after it has been zinc spayed and primed. I do feel that the powder processes have improved over the last few years (especialy compared to TVRs efforts).
I have until thursday to decide and i would like not to have to do this job twice or have a finish i would no be happy with.
Thanks in advance Mark
I make equipment that is used by farmers and is exposed to the elements, mud, and acid. Out of all the coatings we have tried, proper powder coat is by far the best. If it is not correctly applied then it is worse than nothing because it will peel away from the surface and trap moisture. If the surface is properly cleaned primed and passivated, and good paint is properly applied and baked then not a lot will protect it better. Important thing is to ensure the painter knows what he is about and has etch and rinse tanks that will take the entire chassis.
An even better choice would be a polymer 11 Nylon dip (Rilsan or the like) that really is tough but doubt you would find anybody able to do a chassis size bit in Rilsan
An even better choice would be a polymer 11 Nylon dip (Rilsan or the like) that really is tough but doubt you would find anybody able to do a chassis size bit in Rilsan
steve-v8s said:
I make equipment that is used by farmers and is exposed to the elements, mud, and acid. Out of all the coatings we have tried, proper powder coat is by far the best. If it is not correctly applied then it is worse than nothing because it will peel away from the surface and trap moisture. If the surface is properly cleaned primed and passivated, and good paint is properly applied and baked then not a lot will protect it better. Important thing is to ensure the painter knows what he is about and has etch and rinse tanks that will take the entire chassis.
An even better choice would be a polymer 11 Nylon dip (Rilsan or the like) that really is tough but doubt you would find anybody able to do a chassis size bit in Rilsan
An even better choice would be a polymer 11 Nylon dip (Rilsan or the like) that really is tough but doubt you would find anybody able to do a chassis size bit in Rilsan
I agree powder coat is very resilant if applied correctly, ive had alot of powder coating done on motorbike frames and components some good some not so good, all down to monday morning or friday afternoon syndrome
Still think its the best coating for a chassis, but remember you might have to get a file/Dremmel/tread tap out to remove any access coating, I know it can be difficult to mask of areas due to the heat the chassis is exposed to. What a lucky fellow you are to have a separated chassis to play with - stuff of dreams for a serial car restorer.
Assuming that this is a Griffith you're going to keep for years and years, if you have any doubts at all about any of the processes then play totally safe. I would be wary of using too much heat, etc.
It might be a bit 'belt and braces' but I would have it grit blasted, repaired, sprayed with several coats of Zinga (96% zinc), sprayed with two coats of POR15 and then top coated in your colour choice. I would then inject Tectyl 506 into the tubes and turn the chassis over a period of a few days to ensure all inner surfaces were coated. I would then spray several coats of Tectyl clear on the chassis (dries hard) before mounting the bodyshell which I would have sprayed with a clear flexible laquer to resist water, etc.
Just my opinion have fun!
Ricardo
Assuming that this is a Griffith you're going to keep for years and years, if you have any doubts at all about any of the processes then play totally safe. I would be wary of using too much heat, etc.
It might be a bit 'belt and braces' but I would have it grit blasted, repaired, sprayed with several coats of Zinga (96% zinc), sprayed with two coats of POR15 and then top coated in your colour choice. I would then inject Tectyl 506 into the tubes and turn the chassis over a period of a few days to ensure all inner surfaces were coated. I would then spray several coats of Tectyl clear on the chassis (dries hard) before mounting the bodyshell which I would have sprayed with a clear flexible laquer to resist water, etc.
Just my opinion have fun!
Ricardo
Thanks for the info guys, it looks like my feelings with powder coating is the way to go, I will just have to be sure the process is done right and i am sure you will agree that the finish of P.C is the way forward.
Ricardo. The body off is not as hard as people have made out in some of the previous posts. After reading for months on the subject i found the best way was to remove just the body and leave engine and all running gear in place. If anyone is thinking about this type of restoration feel free to ask any questions while its all fresh in my mind. My chassis was in perfect condition and needs no repairs and the original powder coat is even still in place. If anyone is thinking about lifting there body, five blokes is NOT enough!!!!! although it can be done but you won't be up to much after.
Oh and before anyone asks why restore if not needed. I am fussy and maybe slightly sad or possibly mad, I also enjoy physical pain, and wasting money. It also makes doing the:
Bushes.
Clutch.
Engine clean.
Drop links.
and all the little jobs that can be very annoying and fiddly jobs very very easy.
Thanks Mark
Ricardo. The body off is not as hard as people have made out in some of the previous posts. After reading for months on the subject i found the best way was to remove just the body and leave engine and all running gear in place. If anyone is thinking about this type of restoration feel free to ask any questions while its all fresh in my mind. My chassis was in perfect condition and needs no repairs and the original powder coat is even still in place. If anyone is thinking about lifting there body, five blokes is NOT enough!!!!! although it can be done but you won't be up to much after.
Oh and before anyone asks why restore if not needed. I am fussy and maybe slightly sad or possibly mad, I also enjoy physical pain, and wasting money. It also makes doing the:
Bushes.
Clutch.
Engine clean.
Drop links.
and all the little jobs that can be very annoying and fiddly jobs very very easy.
Thanks Mark
Edited by marks3drtaz on Saturday 16th December 21:45
Lotus had problems in the '80's with their hot-dip galvanised Europa and Elan chassis as some of them warped, the one I had certainly never seemed quite right. Also you will need to put a spare bolt into every threaded hole in the chassis or you will have to clean out the zinc with a tap afterwards.
Even if you could make a suitable rig you could still have problems with stress introduction at joints, etc. making the chassis liable to future distortion/corrosion problems. I'd definitely go with a 'belt and braces' solution - it may be a bit time consuming compared to hot-dip galvanising, etc. but you'd be sure of what you had and it would lend itself to remedial work in future. I can understand why hot-dip galvanising is used for mass production but you are dealing with a one-off here.
Ricardo
Ricardo
that daddy said:
Now theres a thought, if someone made a jig to bolt to the chassis as it was hot dipped/galvanised so as not to allow twisting/etc.this would be the ultimate solution.
It would be interesting to know if that worked. I'm not quite sure what makes it warp, whether it's existing stresses in the chassis relaxing, or differential contraction as different bits cool off at different rates. I have this image of the chassis being held perfectly straight by the jig, and then going 'twang' when it's released. The people who do the hot dipping would surely know.
until you unbolt the chassis and it bows, you need to put it through a normalising process to make sure it stays straight as even when bolted down the metal can still be under stress. Had this a few years ago at college when making something, was fine until I took it out the clamps and it ended up looking like a banana lol.
I suspect that this distortion problem may be why TVR and other car manufacturers didn't use hot-dip galvanising - it might be okay with a relatively simple two-dimensional object like a field gate but probably creates all sorts of problems with a complex three-dimensional item such as a tubular TVR chassis (don't all hollow items require to be drilled anyway) - anyway IMO it's too big a risk to take with a scarce item like a TVR chassis. I suspect the galvaniser will make you sign a disclaimer just in case.
Play safe and you won't be sorry.
Ricardo
Play safe and you won't be sorry.
Ricardo
GreenV8S said:
that daddy said:
Now theres a thought, if someone made a jig to bolt to the chassis as it was hot dipped/galvanised so as not to allow twisting/etc.this would be the ultimate solution.
It would be interesting to know if that worked. I'm not quite sure what makes it warp, whether it's existing stresses in the chassis relaxing, or differential contraction as different bits cool off at different rates. I have this image of the chassis being held perfectly straight by the jig, and then going 'twang' when it's released. The people who do the hot dipping would surely know.
As far as I'm aware it's the metal itself is stressed in the forming process, the molecules will realign when its heated and the metal can warp when that happens. That's why some metal is normalised (heated and cooled) when manufacturing components but with cast or extruded materials the molecules never realign, same basics to why billet cranks and cams are stronger than cast jobbies. That's what I remember from my manufacturing technology classes anyway, could be jumbled in my brain by now though lol
Just to follow up on the hot zinc subject.
The Zinc is sprayed on to bare etched metal through use of a flame gun which a mix of zinc and some other stange metals are fed into as a solid. The temp on the surface of the object will be under 300c as the idea is to get it to harden on contact. Acording to the company this method was designed for zincing square oil containers and some types of boat hulls to stop warpage. "can make a iron hull last 25 years longer" Also the cost of maintaining a galve tank is 20k p.a without topping up on metal!!! The guy did say that dipping could be done without warpage as the chassis could be dipped cold. The down side to this is the contact time to the metal is very short and would give a very thick and uneven finish also any metal that got inside the chassis would harden before allowing to drain.
THE DOWNSIDE!!!
even coverage can never be guaranteed as this is down to the chap spraying, small and tight areas could also be left uncovered. The coating is seam tight so rust cannot spread from uncovered to covered but as we know it can rust from the inside out!.
This is only what i have been told and to be honest i am still none the wiser but hot spaying it is then as this is better than nowt. Zinga as mentioned earlier is also a good idea as this has a high percentage of zinc content but will not stop rust creep if the surface is damaged also the chassis will have to be transported bare with zero protection and i do not have a etch tank at home to dip prior to painting.
Costs:
Blast £125-150
Etch ind zinc £80-100
Prime and powder £100-125 Also colour could alter cost. How about black chrome as a bmw m3 wheel!!!! Just joking
Thanks again all for your input and i will try to post some pics.
Mark
The Zinc is sprayed on to bare etched metal through use of a flame gun which a mix of zinc and some other stange metals are fed into as a solid. The temp on the surface of the object will be under 300c as the idea is to get it to harden on contact. Acording to the company this method was designed for zincing square oil containers and some types of boat hulls to stop warpage. "can make a iron hull last 25 years longer" Also the cost of maintaining a galve tank is 20k p.a without topping up on metal!!! The guy did say that dipping could be done without warpage as the chassis could be dipped cold. The down side to this is the contact time to the metal is very short and would give a very thick and uneven finish also any metal that got inside the chassis would harden before allowing to drain.
THE DOWNSIDE!!!
even coverage can never be guaranteed as this is down to the chap spraying, small and tight areas could also be left uncovered. The coating is seam tight so rust cannot spread from uncovered to covered but as we know it can rust from the inside out!.
This is only what i have been told and to be honest i am still none the wiser but hot spaying it is then as this is better than nowt. Zinga as mentioned earlier is also a good idea as this has a high percentage of zinc content but will not stop rust creep if the surface is damaged also the chassis will have to be transported bare with zero protection and i do not have a etch tank at home to dip prior to painting.
Costs:
Blast £125-150
Etch ind zinc £80-100
Prime and powder £100-125 Also colour could alter cost. How about black chrome as a bmw m3 wheel!!!! Just joking
Thanks again all for your input and i will try to post some pics.
Mark
beleive me galvanising is a big no,no!
I send about 1 -3 tons of steel fabrications a month to be galvanised and a car chassis would not be up to much when you get it back, apart from the fact that with all the 8mm venting holes that would have to be drilled in each section of the chassis would make it considerably weaker.
if your going to be thorough shot blast, and a couple of coats of 2 pack zinc phosphate primer, with whatever your preference is on top.
just my 5p worth.
I send about 1 -3 tons of steel fabrications a month to be galvanised and a car chassis would not be up to much when you get it back, apart from the fact that with all the 8mm venting holes that would have to be drilled in each section of the chassis would make it considerably weaker.
if your going to be thorough shot blast, and a couple of coats of 2 pack zinc phosphate primer, with whatever your preference is on top.
just my 5p worth.
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