Paint Stripping?

[Quinnf]

Anybody have any unusual success stripping the paint down to bare metal on a 'roid?  On my last engine I spent several days using chemical stripper and a sharp putty knife stripping the paint and primer.  Then I removed the plaster (yes, plaster) filler with a flap sanding wheel on a 4.5" angle grinder.  But I recall a few folks were talking about having their parts hot-tanked.  Never heard whether that woked or not. 

Wonder if there's an easier way.  I'm thinking of renting a sand blasting outfit, or maybe having somebody do it for me.

Comments solicited.

Quinn

[mobile_bob]

if you can find a automotive machine shop with an oakite(sp) tank, take it to them. an over night soak
and the thing will come out virgin iron, just be there when they pull it and either have them steam clean it, or offer
do do it yourself just as soon as it come out. anything that is left on the casting that didnt come right off will be softened to
the point that pressure washing will remove it if you get after it before it dries again.

another alternative used by those in the machine tool rebuilders corner, is to put the casting in a barrel with a tight fitting lid, and spash it good with laquer thinner, and then seal the lid down and leave it for a day or two, the fumes will attack and lift most all types of paint. seems to work very well for those guys, i can't imagine the indians using some kind of epoxy paint that wouldnt be affected by laquer thinner.

oh yes,,, and they too complain about finding fillers use to smooth out their castings as well.
bob g

[mobile_bob]

i believe oakite is a brand name for caustic soda, the tank is heated and the stuff is very aggressive in removing paint etc.
also i should note it is also hard on babbit material, so if you have any bushings that are babbited, either remove them or install a shaft that fits them well.

for some reason it won't harm a cam brg or such if the cam is still in the bushing, but without it eats them up, also don't put anything aluminum in caustic soda, it will eat on it too.

if their solution is fairly fresh and hot, it works exceptionally well, if new and hot and in one of those big dishwasher style units, it take less than an hour to do the job.

well worth every cent they charge.

bob g

[aqmxv]

So far I've found two coats of greeen paint (primer and top I guess), a white filler (I'd believe it's plaster, but I was assuming it was some sort of lacquer putty) and a pink filler that must be some sort of bondo-like styrene/polyester.

The green stuff crazes up and comes off in acetone just as Hotater said in his photo essay.  I've only attempted paint removal on small parts so far.  A little gentle attention with an acetone-soaked wire brush and you're down to whatever was painted in the dusty yard in Rajput.

So far, I haven't attacked a big iron casting yet.  I'd believe tanking is the best solution.  That or media blasting.  If the secret tanking system is just a hot caustic bath, I can do that at home.  Be sure that you have no dissimilar metals around before you go this route.  Light alloys all disappear in strong caustic bath.

[Quinnf]

I tried acetone and it doesn't touch the green paint.  The stripper I used last time was JASCO and it was methylene chloride based.  Nasty stuff. 
I'll try a small piece in some hot caustic soda solution and see if that works.  If successful, then I can make a tank out of a heavy plastic trash can. 

I understand about the dissimilar metals.  I've pulled the parts down to individual castings and even pulled the studs.  Bearings and busihings are safely stored away.

Thanks for the input.

Quinn

[aqmxv]

I should probably mention that I'm SOAKING the parts in acetone for days at a time...  Just painting the stuff on won't work because it's too volatile.

[rleonard]

I cleaned and painted my Lister 16-2 this summer.

I used sand blasting on some components; parts that are removable and easilly cleaned.  I did this on manifolds, flanges, valve covers and the like.  The main block was cleaned with a needle scaler (pneumatic hammer device) and a DA sander where I could get in.  I wiped with acetone and sprayed.  Paint used was Sherwin Williams high solids epoxy.  Came out nice.

Bob
 

[aqmxv]

Pictures?

[Quinnf]

I've got the small crankcase door and dipstick sitting in a 1 liter plastic beaker with some sodium hydroxide (lye) in the lab.  Paint dissolved away in 5 minutes leaving the cast iron surface looking like it had been sand blasted.  The red brick dust filler and the white plaster filler came off quickly, as did the white paint on the crankcase side of the part.  Hot water and continuous agitation (propeller mixer) seem to help a lot.  Lye is available at the grocery store as Red Devil Lye, sold in the laundry detergent and household cleaners aisle.  Looks like 1/2 - 3/4 pound/gallon is what they use.

Looking around on the WWW, it looks like hot tank solutions are sodium hydroxide and calcium hydroxide (lime).  Small parts are one thing.  I'm stressing about stripping the crankcase.  That will need a trash can, methinks. 

Quinn

[Twinscrew]

Quinn, I hot tank my own stuff at home with the following method:  Arrange 3 cinder blocks under a steel 55 gallon drum in a triangular fashion, with only a couple of inches from each block under the barrel. Place all of the parts to be cleaned in the drum and fill with water to 4 or 5 inches above the parts. Add 2 bottles of Red Devil Drain Opener carefully, wearing eye protection (can cause permanant eye injury). Start a fire under the barrel using anything from charcoal to old pallets to just plain firewood. Build the fire around the barrel and keep fed and burning for 4 or 5 hours. This makes any ferrous alloy look brand new whether it's a cast iron engine block or a set of steel vehicle wheels. Again, this is what works for me. This has the potential to be dangerous simply because of the open fire. I don't want to be held liable for anyone that lacks the common sense to do this safely.   

[aqmxv]

Quinn,

So you're a lab rat?  I used to be - do IT now.  I must admit that it was handy having the chemistry stuff around to play with - I still miss the 10 L sonicator bath for parts cleaning...

In any case, I seem to remember that galvanized metal doesn't do well with NaOH solutions, so choose your trashcan carefully. A trashcan full of hot lye water can be an exciting thing to have around.  I use it for a parts degreaser (corvair parts can be as greasy as diesel parts).  Good to hear that a stirred hot lye solution does the trick so easily.  Now I just have to get up the nerve to attack the gib keys...

[Quinnf]

Yes. I work in R&D for a midsize pharmaceutical company.  Did biotech work for 5 years first, some neat stuff, but kept having startups die under me, so went into pharmaceuticals and haven't looked back in 20 years.

Looks like the "weekend chemists" have made it difficult for the rest of us to get lye in areas where there's meth lab activity.  Will do some checking locally and see if there are restrictions here.  If so I might try the saturated acetone atmosphere method.  Used to be able to get methylene chloride or trichloroethane.  Dump parts in the bottom of a steel drum, dump in the TCE and the atmosphere would saturate up to a point on the wall of the drum.  Reflux ring would form at that level and condensing vapor would wash the grime off parts just like a parts washer. 

I'm aware of the problem with aluminum and galvanized steel, so won't make that mistake.  I'm probably limited to a plastic drum and domestic hot water so will have to make a more concentrated solution and maybe keep it hot using insulation, an immersion heater and agitation.

Thanks for the imput.  Wish me luck.

Quinn

[aqmxv]

Danged tweakers!  I have to show ID now to buy common solvents I use all the time.  I wasn't aware lye was getting hard to find as well - it's the only drain cleaner I ever use - or want.

Fortunately, I haven't had much trouble finding it lately.

I worked in environmental chemistry for ten years.  Did analytical work contracted to EPA.  Very educational.  Private industry might be badly run, but it does ultimately have a profit motive...

[Doug]

Loctite brand gasket chisel seems good at removing everything I've used it on, even glyptal 1201 doesn't stand up too it....

A trip to the local highschool might turn up a hot tank, a teacher and class of students that would like to see a Listeroid once its explained to them its a 1930's engine that stood the test of time.

Doug

[Quinnf]

Doug,

You'd be surprised. 

Woodshop.  Gone.
Metal shop.  Gone.
Auto shop.  Gone.
Mechanical drawing.  Gone.

They're not teaching kids how to DO anything manual anymore.

Quinn