I have a friend who wants to use a chemical dip to remove paint from
automobile parts, e.g. doors or hoods.

I am a chemist and suspect the dip is a fairly concentrated sodium
hydroxide solution. I can help him with handling chemicals but would
appreciate some words of wisdom on what is used commercially for this
purpose.

He has told me that they put the parts in a tank and let them soak
overnight or longer. That pretty much eliminates strong acids. I
suggested he go to the junkyard and get a trashed hood or fender and
cut up small squares and experiment with a strong base but if the
process is known on this group he would have a head start.

TIA

"Unknown" wrote in message
...

I have a friend who wants to use a chemical dip to remove paint from
automobile parts, e.g. doors or hoods.

I am a chemist and suspect the dip is a fairly concentrated sodium
hydroxide solution. I can help him with handling chemicals but would
appreciate some words of wisdom on what is used commercially for this
purpose.

He has told me that they put the parts in a tank and let them soak
overnight or longer. That pretty much eliminates strong acids. I
suggested he go to the junkyard and get a trashed hood or fender and
cut up small squares and experiment with a strong base but if the
process is known on this group he would have a head start.

Most alkyd-based paints respond well to alkali treatment. Acrylics and
urethanes may require a chemical stripper containing methylene or ethylene
chloride. This stuff most often is offered in a 'gel' that skins
agressively on exposure to air, to provide a protection against the
solvent's evaporating during its residence time.

The alkali treatments actually break down the paints, and allow fairly
leasurely removal of the residue. The ethylene chloride removers eventually
dry completely, leaving a lumpy residue that is almost as difficult to
remove as the original paint.

Both require skin protection, and the solvent-based materials require
organic vapor filter breathing protection -- they're virulent liver toxins.

There exists a paint removal 'system' consisting of the chemical component
and a fabric "peel" layer that both holds the actives in contact with the
work and which adhere to the paint, allowing it to be stripped off simply by
peeling off the fabric.

LLoyd

Unknown wrote:
I have a friend who wants to use a chemical dip to remove paint from
automobile parts, e.g. doors or hoods.

I am a chemist and suspect the dip is a fairly concentrated sodium
hydroxide solution. I can help him with handling chemicals but would
appreciate some words of wisdom on what is used commercially for this
purpose.

He has told me that they put the parts in a tank and let them soak
overnight or longer. That pretty much eliminates strong acids. I
suggested he go to the junkyard and get a trashed hood or fender and
cut up small squares and experiment with a strong base but if the
process is known on this group he would have a head start.

TIA

Most current auto finishes are very hard to remove without using
organic solvents like methylene chloride. I have seen some strippers
that are supposed to work that are based on orange-peel extracts, very
slow from what I've read, but "green". The stuff I use is called
Aircraft Finish Stripper, I used to get it from an auto body and paint
supply place. Kind of expensive but strips the factory finish in less
than 15 minutes at room temperature from most car parts. It has more
methylene chloride than hardware store paint strippers, they won't even
start to soften auto finishes before they evaporate. Solvent-proof
gauntlets, eye protection and good ventilation are needed, also running
water. The goop that results is considered toxic waste, means of
disposal needs to be found before starting a project. The steel needs
to be protected right after stripping or it will flash-rust and cause
problems with repainting.

We used to use a tank of stripper for removing dud powder coating from
motor home trim parts. It took most of a shift to soften the stuff
enough so it could be hosed off, the tank contents were sealed with a
water cover. The stripper was almost entirely methylene chloride.
This is probably what's used commercially in restoration businesses.

Alkali strippers are good for finishes based on natural oils, like
old-fashioned wood finishes, varnishes and paints. You can't saponify
urethanes or acrylics, though.

Stan

In article .com,
wrote:

Unknown wrote:
I have a friend who wants to use a chemical dip to remove paint from
automobile parts, e.g. doors or hoods.

I am a chemist and suspect the dip is a fairly concentrated sodium
hydroxide solution. I can help him with handling chemicals but would
appreciate some words of wisdom on what is used commercially for this
purpose.

He has told me that they put the parts in a tank and let them soak
overnight or longer. That pretty much eliminates strong acids. I
suggested he go to the junkyard and get a trashed hood or fender and
cut up small squares and experiment with a strong base but if the
process is known on this group he would have a head start.

TIA

Most current auto finishes are very hard to remove without using
organic solvents like methylene chloride. I have seen some strippers
that are supposed to work that are based on orange-peel extracts, very
slow from what I've read, but "green". The stuff I use is called
Aircraft Finish Stripper, I used to get it from an auto body and paint
supply place. Kind of expensive but strips the factory finish in less
than 15 minutes at room temperature from most car parts. It has more
methylene chloride than hardware store paint strippers, they won't even
start to soften auto finishes before they evaporate. Solvent-proof
gauntlets, eye protection and good ventilation are needed, also running
water. The goop that results is considered toxic waste, means of
disposal needs to be found before starting a project. The steel needs
to be protected right after stripping or it will flash-rust and cause
problems with repainting.

We used to use a tank of stripper for removing dud powder coating from
motor home trim parts. It took most of a shift to soften the stuff
enough so it could be hosed off, the tank contents were sealed with a
water cover. The stripper was almost entirely methylene chloride.
This is probably what's used commercially in restoration businesses.

Alkali strippers are good for finishes based on natural oils, like
old-fashioned wood finishes, varnishes and paints. You can't saponify
urethanes or acrylics, though.

Stan


Dunno about using it for "dip-tank" style work, and maybe questionable
from a "The environuts would have kittens" perspective, but there's
always the concept of soaking a few burlaps sacks in brake fluid, then
laying them on the part you want the paint off of. I don't think I've
encountered any kind of coating that stuff won't lift. Once saw the
stuff wreck the finish on a toolbox when mobody noticed that a rag that
had been used for cleaning up a BF spill had been dropped on it just
before heading out for lunch. By the time we got back from lunch, the
finish on the toolbox had blistered up so much that it practically
jumped off the metal by itself - hitting it with a garden hose would
have been all that was needed to get a naked-metal surface.

Of course, that treatment would have to be followed by careful cleanup
and prep to avoid leaving any of it behind to wreck the new finish...

--
Don Bruder - - If your "From:" address isn't on my whitelist,
or the subject of the message doesn't contain the exact text "PopperAndShadow"
somewhere, any message sent to this address will go in the garbage without my
ever knowing it arrived. Sorry... http://www.sonic.net/~dakidd for more info