Hi guys, I am thinking about to take my bonnet down to the strippers. They use a vat to dip the bonnet in and the acids strip the paint (I've been quoted $80). I'm guessing this process will melt all the sealants away on the underside so what I'm asking is, will there be any adverse affects by doing so and is it relatively simple to re-seal it?
Anyone here had theirs done?
Acid dipping bonnet
Started by
_Eddie_
, May 27 2006 10:14 AM
18 replies to this topic
#2
rodomo
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Posted 27 May 2006 - 10:34 AM
Take a pic of the underside before it goes and use urethane when it comes back.
#3
knoath
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Posted 27 May 2006 - 10:43 AM
Please explain?
What do you mean by this rodomo?
I understand about the sealant under the bonnet, but how do you reapply it?
What do you mean by this rodomo?
I understand about the sealant under the bonnet, but how do you reapply it?
#4
_Eddie_
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Posted 27 May 2006 - 10:54 AM
I'm guessing you gotta some how squeeze it up between the under brace and the sheet metal on top in order to glue it down. I think thats why it's there, as an adhesive?
#5
_Eddie_
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Posted 27 May 2006 - 12:13 PM
Question 2: Are there any practical methods of rust protecting the inaccessible areas under the bonnet, specificly, in and around the bottom support brace?
#6
rodomo
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Posted 27 May 2006 - 12:20 PM
Yes it is an adhesive rather than a sealant in this application. Its purpose is to stop the big flat panel of your bonnet vibrating. I will try to post a pic later. At the moment photo bucket is having an oil change or something. 
What car is it for? I have an LJ bonnet or a bent UC bonnet for pic.
What car is it for? I have an LJ bonnet or a bent UC bonnet for pic.
#7
_Pete_
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Posted 27 May 2006 - 12:40 PM
Chemically dipping a bonnet will remove everything as you suspect including any paint and sealers from the underside, I'd be worried about not being able to get any coating on the insides of the bonnet underside ribs to prevent future rust, As Rodomo says you can re-apply the Urethane adhesive between the ribs and the bonnet skin, If you don't reapply this your bonnet will be like a Rolf Harris Wobble board which will be entertaining but somewhat frustratingly annoying not to mention make it hard to do any repairs to the bonnet as the skin will have a tendency to want to walk around on you.
I'd recommend paint stripping the topside and if they're is a need to baremetal the underside, maybe trying to find a blaster who blasts using baking soda or a similar car panel friendly abrasive. Failing that I'd go to town either with a 3M Clean 'n' Strip wheel or paint strip it carefully.
The Sealer/adhesive you'd need is just good old Black Sikaflex, there are other brands available to from Wurth etc.
I'd recommend paint stripping the topside and if they're is a need to baremetal the underside, maybe trying to find a blaster who blasts using baking soda or a similar car panel friendly abrasive. Failing that I'd go to town either with a 3M Clean 'n' Strip wheel or paint strip it carefully.
The Sealer/adhesive you'd need is just good old Black Sikaflex, there are other brands available to from Wurth etc.
Edited by Pete, 27 May 2006 - 12:41 PM.
#8
_Eddie_
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Posted 27 May 2006 - 06:45 PM
As far as I can tell, Holden made no attempts to apply protective coating on the underside of the bonnet in the confined areas. Correct me if I am wrong, but I think it's just bare metal under there?
#9
_Pete_
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Posted 27 May 2006 - 07:03 PM
I think you'd find the steel has some kind of protective coating of some sort most likely some kind of electrostatic primer, I'm not completely sure i've never unpicked a torana bonnet skin before, I had all my door hinges dipped by a mate who has an engineering company that removed all the paint etc and now there is rust stains coming out of the insides of the hinges as any protective coating they had has been removed and I musn't have got enough paint inside them to protect them.
I guess you could flood enough primer in there to get some coverage and then rub out any runs prior to paint, maybe even use a flexible extension on the end of the gun to get into the tight spots.
Theres probably not too much of an isssue of the bonnet rusting away, if its lasted this long its more than likely gonna survive another 30yrs, I think there might be a chance of rust stains ruining the paint finish later on.
Maybe another option is after its dipped cut the inner skin off, prime the underside then weld a smooth sheet of steel in place so its a nice smooth show car like effect when you pop the bonnet. Like a smoothed out Hot Rod!! or like Dynosteves SMOTY LJ , might have to check underbonnet clearances but it would look awesome!!
I guess you could flood enough primer in there to get some coverage and then rub out any runs prior to paint, maybe even use a flexible extension on the end of the gun to get into the tight spots.
Theres probably not too much of an isssue of the bonnet rusting away, if its lasted this long its more than likely gonna survive another 30yrs, I think there might be a chance of rust stains ruining the paint finish later on.
Maybe another option is after its dipped cut the inner skin off, prime the underside then weld a smooth sheet of steel in place so its a nice smooth show car like effect when you pop the bonnet. Like a smoothed out Hot Rod!! or like Dynosteves SMOTY LJ , might have to check underbonnet clearances but it would look awesome!!
#10
_Eddie_
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Posted 28 May 2006 - 01:29 AM
Ha Ha! Maybe if I had already spent a billion dollars on it to make everything else perfect I could justify a show-like finish on my bonnet. But with my humble budget I will just make do with what I can and see if I can get as much protective coating as I can down there and let the person who has it in another 30 years worry about it. After all, isn't that really what the Holden spirit is about? Passing the dodge onto some other poor basturd?
#11
GML-31
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Posted 28 May 2006 - 06:51 AM
you may find it cheaper just to get a better bonnet that just needs priming and painting???
#12
_Bomber Watson_
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Posted 29 May 2006 - 07:45 PM
personaly i would fill all the braces up with tectyl then seal the LOT with sickaflex. around all the gaps. the way i shoulda done mine. if you run a line of masking tape along the edjes where you want the sickaflex to end and squeeze it in in a nice even bead it looks real profesional, i do this at work.
#13
_FCCOOL_
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Posted 29 May 2006 - 09:57 PM
remember all primers are porous exept for epoxy primer, normal 2k etch, hs and acrylic primers will turn to rust if exposed for to long. another advantage of epoxy is you can apply filler over the top.
if you get it acid dipped you will need to get the paint right into the crevaces or it mightl drip orange stuff when your car gets wet.
if you get it acid dipped you will need to get the paint right into the crevaces or it mightl drip orange stuff when your car gets wet.
#14
_Eddie_
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Posted 31 May 2006 - 09:06 PM
Thanks for everyones input so far...I should get the bonnet back from the strippers either tomorrow or friday. I'll use the products you guys suggested to re-seal it but I'll have to figure out a way to protect the underside (unless Pete you wanna come over and weld me up flashy shit? he he). One idea is I could pour protective coating down the holes and flood the area with the paint. Pretty crude way of doing it, but it should reach all the nooks and crannies.
Anyway that's one way, does anyone else have any others? For my way to work the product ideally would be ok to apply to bare metal, be relatively runny, and can have top coats put over it (not essential tho). Any ideas of a suitable product?
Anyway that's one way, does anyone else have any others? For my way to work the product ideally would be ok to apply to bare metal, be relatively runny, and can have top coats put over it (not essential tho). Any ideas of a suitable product?
Edited by Eddie, 31 May 2006 - 09:10 PM.
#15
_Pete_
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Posted 31 May 2006 - 09:34 PM
I'd be just flooding the inners with paint as you said,primer first then your top coats, You'll never really get enough of anything else in there to make any difference, maybe some extra rust proofing sprayed on after you've painted if you don't mind it looking a touch messy (most new cars cop this anyway).
I think it would look a bit messy trying to urethane seal the entire area, some might say it would look a bit dodgy and you'd run the risk of sealing the air inside which will expand and contract with the difference in temps and most likely buldge your bonnet on a hot day, I'd just re-apply whats been stripped out to secure the skin to the inner frame.
I'm thinking i'll skin the inners of my bonnet and boot lid when I do the rebuild of my LX so its nice and smooth, I think it looks pretty nice and it really wouldn't be a hard job maybe just a little time consuming particularly all the welding and grinding but still not rocket science.
I think it would look a bit messy trying to urethane seal the entire area, some might say it would look a bit dodgy and you'd run the risk of sealing the air inside which will expand and contract with the difference in temps and most likely buldge your bonnet on a hot day, I'd just re-apply whats been stripped out to secure the skin to the inner frame.
I'm thinking i'll skin the inners of my bonnet and boot lid when I do the rebuild of my LX so its nice and smooth, I think it looks pretty nice and it really wouldn't be a hard job maybe just a little time consuming particularly all the welding and grinding but still not rocket science.
Edited by Pete, 31 May 2006 - 09:38 PM.
#17
_finer70_
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Posted 01 June 2006 - 08:03 PM
When it comes to dipping it can be either acid or caustic.
Both are effective strippers. Acid needs to be fully and totally and fully and totally removed to prevent it continuing to work on the metal or leaving it bare for oxidation (RUST).
Caustic stripping is different. Being alkaline it is kinder to the metal and actually leaves a surface coating that if kept dry will remain rust free for 6 month.
The only treatment necessary before painting is to apply a water like phosphating compound which will form a paint friendly coating.
Applying too much sealant in an attemp to protect hard to get at areas can work against the intention you want. It may trap condensation and promote corrosion. If it were not sealed with air able to flow and keep it dry it may well be better.
Anti rust compounds and fish oil can be sprayed into these areas and keep the hungry beast (rust) at bay.
I have had two LC bodies fully caustic dipped and had NO problems with resealing joints etc. I flooded all seams with phosphating compound, let them thouroughly dry and them applied factory quantities of seam sealant compound.
As for sand blasting, you simply need to get someone who knows what he is doing. There is no reason for a panel to be damaged by sandblasting. If it is damaged it just shows the person doing the job does not know how to do it, or he is using an indusrtial sand blaster with too high a pressure. The right tool and the right tradesman will always give the right result. Trouble is finding them.
Both are effective strippers. Acid needs to be fully and totally and fully and totally removed to prevent it continuing to work on the metal or leaving it bare for oxidation (RUST).
Caustic stripping is different. Being alkaline it is kinder to the metal and actually leaves a surface coating that if kept dry will remain rust free for 6 month.
The only treatment necessary before painting is to apply a water like phosphating compound which will form a paint friendly coating.
Applying too much sealant in an attemp to protect hard to get at areas can work against the intention you want. It may trap condensation and promote corrosion. If it were not sealed with air able to flow and keep it dry it may well be better.
Anti rust compounds and fish oil can be sprayed into these areas and keep the hungry beast (rust) at bay.
I have had two LC bodies fully caustic dipped and had NO problems with resealing joints etc. I flooded all seams with phosphating compound, let them thouroughly dry and them applied factory quantities of seam sealant compound.
As for sand blasting, you simply need to get someone who knows what he is doing. There is no reason for a panel to be damaged by sandblasting. If it is damaged it just shows the person doing the job does not know how to do it, or he is using an indusrtial sand blaster with too high a pressure. The right tool and the right tradesman will always give the right result. Trouble is finding them.
#18
_Eddie_
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Posted 01 June 2006 - 09:06 PM
Good info there mate, you'll have to tell us more about this phosphate compound -where you get it, what brand to look for etc. Can you apply paint over the top? For the record, my bonnet is getting caustic stripped and should get it back tomorrow. I think they water blast it after they pull it out of the dip but I'm totally sure if they add any chemicals to it. From what they told me I should be able to apply paint straight onto it as long as it not left too long.
#19
_finer70_
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Posted 02 June 2006 - 06:57 AM
The caustic dipper gave me the phosphate compound to use. Ask your bloke about it.
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