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Tips

To dip or sandblast the AH frame

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dvu101

Jedi Hopeful
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I am approaching the point where I would be stripping my AH frame.
Which is the best way to do that?

Do I do the frame welding before stripping? It looks like the stripping will likely find more areas to fix.

What kind of primer should I use?

How soon after stripping should I prime?

How soon after I prime do I have to paint the final paint over the primer?
I heard I have to paint soon after I prime.


Thanks for your experience guys.

Scott
 
Hi Scott,

Why not get prices for abrasive blasting and dip stripping and see if that sways your decision on how to approach the paint removal. If you end up blasting it, degrease everything thoroughly beforehand.

Blasting gives a very good finish for applying primer whereas dipping has the potential in the hands of an inexperienced operator to cause merry heck with paint adhesion if any acid/chemical is present in the seams after dipping. My chassis was acid dipped then epoxy primed but it didn't stick very well so I'm going to remove the paint and start again this summer. I haven't decided yet whether I'll get it blasted or just take to it with paint stripper and sandpaper.

Painting as soon as possible after the bare metal is exposed is advisable to prevent flash rust forming. At least within a day and if your workshop temperature falls below the dew point at night then before night as the moisture in the air will condense on the unpainted surface and start rust forming.

Lots of people use epoxy primer onto steel, there is also polyurethane DTM (direct to metal) paint. Epoxy can be sprayed with a suitable respirator but you'll need a air-fed breather/visor and spray suit plus a spray booth for isocyanate DTM. I used LIC40 polyurethane on the panels because it can be left indefinitely without overcoating and can be tinted to any colour including the original dark brown and red-oxide the factory used.

Any 2-pack paint can be overcoated without scuffing within about 24 hours of applying the previous coat, i.e. before it has fully hardened. After that you have to scuff it all over with Scotchbrite pad or similar to give the new paint something to stick onto.

It's up to you whether you do the repairs before or after stripping the paint and it really depends on how much damage there is that will be exposed after stripping that you might miss beforehand. If your chassis is anything like mine there'll be so many areas that need attention it is cheaper to replace the whole thing with a new one. Mine needed all outriggers, both inner rocker panels, both main chassis rails due to cracks around engine and suspension mounts, a bend in each rail below the diff, front and rear members badly dented due to jacking damage... Combine this with a crack in the gearbox tie-bar attachment point, cracked handbrake attachment, rusted out engine bay braces, rusted rear bumper attachment bars. It just became too much work to put right and I'm very glad the guys here convinced me to go that route.

Andy.
 
dvu101 said:
I am approaching the point where I would be stripping my AH frame.
Which is the best way to do that?

Do I do the frame welding before stripping? It looks like the stripping will likely find more areas to fix.

What kind of primer should I use?

How soon after stripping should I prime?

How soon after I prime do I have to paint the final paint over the primer?
I heard I have to paint soon after I prime.


Thanks for your experience guys.

Scott
Click to expand...
Maybe the "Frameman" will chime in on this? He did my new frame and I know that the first thing he does is to strip the frame by snadblasting it to see the extent of the damage to the frame and chassis, etc. I have photos of the frame when it was blasted and it was in worse shape than I originaly thought.
 
I think dipping will do a better job of removing all the rust and paint, particularly on the inside of the chassis rails. BUT ... once you get rid of all those things, you need to find a way to coat the exposed surfaces (including inside the chassis rails) as quickly as possible to prevent rusting. Some dippers will use a phosphate coating to inhibit rust, but even then you don't want to let it stand around too long uncoated. One disadvantage to dipping is the chemicals can ooze and drain for some time and cause problems with new paint surfaces. The real trick is going to be able to coat the inside of the chassis rails either by using a spray wand and spraying epoxy paint or Waxoyl inside or as some restorers do, pouring liquid epoxy paint inside the rails and sloshing it around by moving the chassis around (helps to have it on a rotisserie)
 
We did a dip and a process immediately after called E-coating. That is what all modern auto manufacturers use on all metal parts. It coats everywhere as it is a dip process also.
 

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I saw a new process that used an abrasive in water. Since the water keeps everything cool, it can even be used on panels. It looked interesting anyway, and the plus is that they can do it in a driveway since it makes no dust and washes away.
 
I strongly recommend you do not dip the chassis. Chemicals may appear to remove the rust from the exterior of the chassis but it does not dissolve rust. We have had several chassis that have come into our shop that have been dipped and when we cut them apart there is a significant amount of rust residue on the inside of the chassis rails which holds the chemicals used for the dipping process. I understand dippers claim to neutralize the corrosive acids, I find this not to be true. I always sandblast at the beginning of a project. We do not prime anything until after we have done our repairs. The primer will contaminate the welds. When all repairs are done we wire brush the entire superstructure, wash it down with metal cleaning solvents. We have pictures of this on our web site. After the structure is clear we use a zinc chromate primer ,then seam seal it then reprimer. There is a 7 day window from the time you prime to the time you apply paint. If not done within 7 days the primer must be sanded. Any chassis' that are dipped will present paint issues once the acid begins to creep and seep.
Quality metal does not rust quickly but weak metal does rust quickly.
Marty
 
You would have to uncap every enclosed section- the two main rails, 4 outriggers, the front and rear cross members and the X member and removing all the residue would be the only way I would know how to get it out.
 
Frameman said:
You would have to uncap every enclosed section- the two main rails, 4 outriggers, the front and rear cross members and the X member and removing all the residue would be the only way I would know how to get it out.
Click to expand...

What I meant was if someone decides to sandblast and not to dip to avoid the issue of the "junk" left inside the enclosed sections, how do they stop the rust on the inside of the frame rails?
 
There is no way that I know of, to stop rust once it starts I'm afraid. You can try oil coating. For the E coating process to work it should be applied to clean surface so it is difficult to do inside the rails. Although there are processes that prevent rusting unfortunately once the deterioration has started it is difficult to stop. Some people do a process called hot dipped galvanizing. A process that galvanizes the metal components but like the E coating process problem, it may be difficult to tell if every thing is covered on the inside. I think this would be the better choice of the two.
 
The E-coating that was done on our cars was a dip process, so anywhere the solution can flow, it covers. I can guarantee I have 100% coverage inside and out on the 2 cars we have done so far with this company.
 
HealeyRick said:
What I meant was if someone decides to sandblast and not to dip to avoid the issue of the "junk" left inside the enclosed sections, how do they stop the rust on the inside of the frame rails?
Click to expand...
How about Waxoyl?
 
I had my TR3A frame blasted here in Sacramento and then they painted an expoxy primer on the bare metal. The primer is very thick and stuck very well. So the blasting process was about $2K and the painting was about 1K. I then painted the frame with urethane one stage . Very hard once it dries. I did some minor welding on the frame for repairs prior to the blasting. It did not need anything after. It all depends on your frame. A TR3A frame is much thicker than a Healey.
Jerry
BJ8 (frame made by Frameman)
TR3A
68 Austin Mini
 
rjc157 said:
how much does something like that cost
Click to expand...

If I recall correctly it was about 1700. The speedster we did we dipped, then took it home and did all repairs, then brought it back and redipped then E-coated. That was about 3 grand total I think. I could check tomorrow for sure in the file out in the shop, but I think those are fairly close. That was 3 and a half years ago for the Healey though, and about 5 or 6 years on the speedster. And guess what..... I still don't see that "chemical reaction" that people warn about with dipped cars.
 
I second the non use of chemicals.......in visualizing the penetration of the chemicals, and then the neutralizing agents, It seems to me the neutralizing agents won't really penetrate as far as the acid, leaving areas where acid is still active....but just my ranting...not proven in fact. Unfortunately, it takes a very long time to prove the acid will never fail the paint system, but I've heard of instances of that happening....not saying that improvements haven't been made to the compenents or the processes.

I personnally had my frame blasted, not sand blasted but mineral blasted by a firm in Sacramento. They use a material similar to soda, but darker and apparently better in removing the rust. The particles are very fine, able to penetrate the fine pits made by rust but not heavy enough to warp the sheetmetal frame/substructure. Then I had them apply the epoxy primer to the frame, and they did uncover areas that were not apparent initially that had major rust damage. I repaired the rust damage afterwards and applied epoxy primer to repaired areas after the blasting/primer. I painted afterwards, some years later, after roughing up the primer with scuff pads. I also left the removed blasted and primered sections of a fender out in the weather for a few years to see if the process was effective, and I'm happy to report no rust surfaced. So far so good after about 10 years, but then I don't drive in the rain if I can avoid it....but then we live in Oregon...so its a difficult proposition.

As for stopping the rust inside the frame, I just used a 3M product, similar to waxoyl. All you need to do is stop the moisture from penetrating, and from the thickness testing I did on the frame, internal rust wasn't really an issue. If you do have major internal rust, then frame replacement should be considered. There are also rust conversion products the would work also, if it isn't serious.
 
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