Primarily Petroliana Shop Talk Forums Shop Talk Petroliana Forums Showcase and Stories, Petroliana ROTM - June - Metal Stripping

Hey you oldgassing curious restorating petro nuts, how's it going??

This month, Jason, the normal ROTM guy (I guess that menas I'm the "abnormal" guy) has handed the torch to me until he gets his new house and yard squared away.

GOOD NEWS JASON, IT'LL BE WORTH IT, BAD NEWS JASON, IT'LL TAKE A BUCH OF BLOOD, SWEAT, TEARS AND TIME!

I've got a few steaks to throw on the grill, a few squash to fry and a couple of cukes to cut up. After that's done and consumed I will start more of my freakish rambling on oldgas. A new temporary format I have been asked to handle is some TECH TALK. I figure metal stripping is a good starter being that's one of the first comlexities to tackle restoring a pump.

See ya shortly,

Neal

Okay, before I start talking about what I know about metal stripping, I'm hoping some fellow oldgassers will fall in and share what they know about the following methods;

Sandblasting
Electrolysis
Chemical stripping
Heat
Sanding & grinding

I know a little bit about some of the above methods and a lot about 2 or 3 of them. I will certainly try to carry what's being discussed here but multiple heads are far better than my one.

Also there may be some other effective methods than what I've mentioned above. We've got a month to cover metal stripping so the way I see it a lot of detail can be gone into on them each.

If you guys will get the ball rolling I'll handle it during the lulls.
Thanks, pitch in, learn and enjoy,

Neal

I am partial to what I guess would be chemical striping. I use a hot tank, same as any auto machine shop. It is verry easy not much labor. You just submerge for the day, and rinse. The chemical I use is a "soap" from ZEP. works well. The only down side to this I see is if there is a double layer of the steel. It is hard to get all the chemical out from in between. If this is not done it will come back to haunt you while wet sanding. Learend this the hard way. This is what I belive to be the gentalist to the metal.
I also use several blasting tecniques mostly on the frames and cast parts. High preasure blasting can be disatorus to sheatmetal. Tokheim 39 doors are exspecially vulnerable to warping. If rust is left I use a blast cabnet with alumnium oxide to dust off the surface. I turn it down to 60psi and use a good angle to hit the rust. Direct preasure can warp more easily. Also sometimes I use 100 grit on a DA sander to work the surface rust. The key is patience. Some people use sandblasting, if you have someone who you know can do it with out warping the metal then thats fine but finding some one can be expensive if the ruin a hard to find piece. I like to do as much of the project as I can, so I use the means I have. One other thing to sandblasting is it will work harden the surface and that is hard on your metal file. These are just my oppinions and things I have tried. I cant wait to see how others do it. I learend alot of paint tricks to try last month, and cant wait to learn more this time. Keep it comeing please!
Thanks for doing this Neal
Brandon

Can you tell us exactly what the name of the 'soap' is from Zep? Is it diluted etc. Is it heated. I would like to try it. Generally when anything is what I call acid dipped, You can neutralize any remaining acid or chemical by spraying it down good with white vinegar. Then rinsing with water.. The vinegar in a squirt bottle can be directed at any seams and really flush the hidden acid out. The acid is what comes back to bubble the paint after you think you have done a premo job. Lets hear from some more guys! Larry

Larry, I've had zero experience using chemical stripping but here's a link that will put you in touch with ZEP.
http://wrrc.p2pays.org/vendor.asp?ID=3827

I couldn't find a ZEP website on the net but hopefully a phone call will answer your question (which I hope you'll share with us).
Regarding chemical stripping, two things stick out in my mind;

1- A guy I know that restores cars said that he has used a chemical stripping company in Greensboro NC with much success EXCEPT at one point he had a hood that had a crimped lap seam which bled some stripper about a year after he finished the car, HE SAID GETTING IT TAKEN CARE OF WAS A NIGHTMARE!!

2- In the electric motor rewind business (that I was in of for 25 years), one of the processes for stripping stators was a chemical process. During the late 70's one of my competitors in town exclusively used that chemical system instead of the standard burn-out oven that was pretty much the SOP. The chemical was called something like trichlorethylene (sic??), there was about 6 inches of it in the bottom of a four foot tall tank. There was an element that heated the chemical which caused the vapors to rise. A water jacket which stopped about 6" from the top of the tank kept the vapors from rising over the top of the tank. A stator or part was hung within the boundaries of the vapor area and left for approx 30 minutes. The varnish, resin, etc. was softened to the point that it became mush. The owner of that shop (a SUPER smart & nice guy) loved this system because it was quick, versus an eight hour burn-out oven cycle. I do remember that you couldn't put aluminum parts in it though. The problem was, out of four young employees, two of them developed cancer in their early 30's. As a matter of fact, the owner died about 3 years ago, guess what he died of!

I pretty much dislike the EPA and pristime tree hugging green people BUT such deadly stuff as trichlor-what-the-heck-ever-you-call-it does NOT need to be a part of our lives.

Thanks for the conversation guys, more to come.

Neal
PS: the burn-out oven mentioned above is one of the metal stripping processes we're going to talk about. Obviously that falls under the "heat" catagory.

Larry I will look at the bucket in the next day or so. It comes in a 150 lb drum. It is used hot it will cut paint if it is cold just takes a couple days. I would say it has some kind of costic in it though, you cant use aluminum in it. I will try the vinigar thing though, or maybe baking soda? Thanks for the info. I have a baking oven and stainless steel shot blaster, wooks great on cast or cast alum. Simple process bake for 30 min at 750 Deg, then put in blaster for 15 min. Looks like brand new cast even a little shine to it. This is whats replacing the hot tank does a nice job. Down fall is one big enough to do visable skins is about 60 grand.
Thanks
Brandon

Since chemical stripping is the current topic, let's run with it. I don't know a lot about chemical stripping but I'll try to BS my way through this.

I suppose the most common chemical stripper would be "Paint Remover" aka "Paint Stripper". Here's the positive sides of using commercially available paint stripper;

* Readily available - Lowes, WalMart, Home Depot, any hardware store, etc.
* Fairly inexpensive - I would guess on a short computer pump it'd take around $20 -$30 to do the entire pump. Of course there are a lot of variables due the thickness of paint, type of paint, number of nooks, crannies and curves, environment of work area, etc.
* Low skill is required to strip with this.

The down side to paint stripper is;

* Requires a lot of work (work as in manual labor). The stripper softens the paint causing it to lose it's adhesion to the metal, but you then have to scrape the gooey mess off. Some tools to try would be a wide putty knife, paint scraper, possibly a scouring pad (coarse steel wool or the red Scotch-Brite pads).
* Skin irritant, also could screw up an eye if a glob ended up there.
* Any hidden residue could mess the new paint up down the road.

There's also companies that have big vats with a stronger and thinner chemical solution, the problem is you got to find a place that does this. For example, New Hanover County has a population of 120K and there's no place that does this. I'm guessing the EPA makes it less desireable to go into this type business. I'm not sure how expensive commercial dipping is, maybe someone could share that info with us.

I'm not sure how well chemical stripping kills rust. I also don't know if the metal has to be treated with a neutralizing agent to get the PH back to 7 (neutral).

Come on oldgassers with experience in this area, spend a few minutes on a reply here and educate us.
Thanks!

Neal

Neal,
Thanks again for taking over the thread. You will do a great job especially since you have so many projects going on and you pay so much attention to detail. Well, back to the landscaping and indoor projects for me..... BTW great topic this month. ~Jason

In stripping cars with multiple layers of paint, I like to use a straight razor blade and handle combo. This is done dry without chemicals. This might sound a little strange at first but it works well. Its some what difficult to initially start. If you can find a scratch, start to push the razor under the paint. Once you get going, the paint chips are flying, and it moves pretty quick. Its a fairly easy clean-up too. Sweep up the chips and you're done. Works well on objects with multiple coats of paint.

Otherwise, the nasty aircraft chemical stripper, a straight razor blade, and a D/A sander are my other favorites.

------------------
-Dave-
Slowly progressing on a '54 Tokheim 39

Thanks for that last reply Dave! You know, I'm sitting here thinking "razor blades and elbow grease, that's fairly inexpensive!". I also like the easy cleanup aspect.

Okay guys, who wants to get the ball rolling on discussing sandblasting? I hate to hog all the air time!!

Later,

Neal

Neal
Just another word on chemical stripping,or
acid dipping.I have had three pumps dipped
over the last two or three years by a place
near me.It did a good job taking off all
paint and rust.Cost was about $110. per
pump.I've had no problem with bleed out
after painting.

------------------
JERRY

Sorry it’s been so long since I last replied to this thread, I took my wife for a 3 day vacation to Myrtle Beach and didn’t take my laptop along. Let’s talk a little about sandblasting;

I figure everyone here knows the elementary things about this;
Sand is sucked or fed into an air stream, the sand impacts the surface, the sharp edges of the sand cuts whatever it hits and bare metal is then revealed.

There are two types of sandblast systems, siphon & pressure fed.
Siphon System- the most common and most economical, the variables available are;
1- air pressure
2- air nozzle size
3- media nozzle size (whatever you’re blasting with, be it sand, glass, etc. is referred to as media)
Pressure Feed System- I am not familiar with this but I know it’s more expensive and takes less air to do the same amount of work. The variables with this system are all the above PLUS better control of the media feed.

The true test of a good sandblast system and operator is sheet metal, especially older sheet metal that is pitted, eroded and without a lot of the mass it had in its earlier days. Gun technique is important, keeping an angle to the work versus head on blasting doesn’t tend to distort the sheet metal. Also on our fragile sheet metal you can turn the air pressure down a little (to around 80 psi versus the normal 100 psi), this is easier on the metal. With a pressure feed system you can also turn the media feed up a little while turning down the air pressure, this works well on fragile metal.

On my sandblast and glass bead cabinet I have the largest air and media nozzle in my guns. Obviously for more detailed work one would want to reduce these nozzle sizes. For the record, when you’re blasting something heavy that’s pretty much bullet proof (like an angle iron frame, cast iron base, etc.), I put the max air (around 100PSI) and the most media (largest nozzle) to it.

A glass bead cabinet is basically the same thing as a full-blown sandblast system except slightly smaller and enclosed within a cabinet. A vacuum cleaner keeps a negative pressure within the cabinet while the work is being done to evacuate the trash (whatever’s being removed form the metal) and to keep it visible within the cabinet so you can see while you’re working. I also keep the vac running so when I open the door I don’t get a lung full of the stuff that’s floating around in there. Usually glass bead cabinets are used for doing finer detailed stripping versus what a sandblaster is used for.
I use my glass bead cabinet for both, I use sand for heavy stripping and then swap it over to glass beads to do finer work. In the standard cabinet media can be removed and different media dumped in within a minute or two.

Here are some facts and things to keep in mind regarding sandblasting and glass beading;
Normal air pressure = somewhere around 100 psi
Air and media needs to be dry
In a glass bead cabinet, eventually the media will need to be replaced. Basically, it gets crushed as it gets used, the media size is constantly getting smaller and the sharp edges (which actually does the work) start disappearing. When sandblasting, new media (sand) is being used and usually not worth being reclaimed.
Minimum size air compressor for a glass bead cabinet = 3 hp. (somewhere around 10 cfm free air specification)
Minimum size air compressor for a sandblast system = 5 hp. (somewhere around 15 cfm free air specification)
Of coarse, the more air the better, heck, professional sandblasters use 50hp+ compressors.
When sandblasting, a fresh air breathing system is a must. Not only is sand bad for your lungs, think about the lead and other bad things that are in the old paint we’re removing!!

For glass bead cabinets the media size is called “sieve size”. The higher the number the finer the media. Of coarse the coarser the media, the more material it removes. The finer media, the more it polishes versus removing material.
Here’s the pecking order of glass bead cabinet media (per my memory) from coarsest to finest;
Sand, ground glass – approx. sieve sizes 25 - 100
Glass beads, aluminum oxide, silicone carbide – approx sieve sizes 100 – 200
Glass beads, aluminum oxide, silicone carbide – approx sieve sizes 200 – 300
Ground corn cobs, ground walnut shells, etc. – strictly for polishing

The above list is pretty much general, there’s much more that could be included but what’s above is about 90% of the deal.

Well, my fingers are getting tired so I gotta go! PLEASE feel free to add anything I missed or correct anything I’m wrong about.
Thanks,

Neal

The next metal stripping process to discuss is heat. I was lucky enough to have spent my career in an electric motor repair shop and exposed to another really neat way to strip metal, our burnout oven. In the business this oven was used to vaporize the varnish and turn the insulation into carbon in a bad stator. When it was determined that a motor winding (stator) was bad and needed to be rewound it was placed into this oven and when the cycle was complete it was removed, the wire stripped out, the core sandblasted and then it could be rewound like new.

The burnout oven slowly ramped the temperature up to 700 F, held it for anywhere from 4 – 10 hours (depending upon the load size) and when it timed out the cool down period was approx 3 – 4 hours. The fact that these ovens gradually heat up, have strict temp controls, and cool down gradually, warping or cracking is never an issue. These ovens come in many sizes, internally ours was 3’ X 3’ X 5’ tall, that means it can do an entire short pump!! Bigger motor shops have bigger ovens.

Regarding metal, the heat vaporizes the paint and kills the rust. Just like with sandblasting, when the metal is stripped it needs to be primed ASAP so it doesn’t start rusting again. When metal is removed from a burnout oven all it needs is blowing off with an air hose and it’s ready for the primer. I mentioned that heat kills rust, when I was a kid I learned that just because you hit a rusty spot on a bicycle with some sandpaper and paint it, unless you removed 100% of the rust and got down to the pure metal the rust will return. Sandblasting removes paint and rust down to the bare metal, that’s why the metal stops rusting. A cycle in a burnout oven vaporizes the paint and rust, it also kills the rust, just remember to get some primer on it quick or new rust will immediately begin.

I know everyone doesn’t have a burnout oven sitting in their garage but if you can find an electric motor repair shop that rewinds motors, they’ll have one. Chances are if you took some parts or even a complete pump (depending upon the size of their oven), tell them to do it as they have room for, along with a little cash, it’d work.

Metal items other than sheet metal can be stripped with a torch if an oven is not on hand. For example, cast iron bases, entire frames, brackets, etc. Just be aware when you’re torching something made of aluminum, a little heat goes a long way. Something that works good for removing paint is to use a cutting tip on the torch, hit the oxygen trigger and you can blow paint off quick, just don’t do this to sheet metal, WARP CITY if you do! If there’s no paint on the metal item it just needs heat from the torch to remove and kill the rust, blasting with a cutting tip really does nothing. Remember, when heating a part with a torch to strip it, don’t get it anywhere near red hot, as I said earlier, the burnout oven which does beautiful work only takes it to 700 F, not the 1500 F that a torch is capable of.

Please feel free to ask any questions or make any comments. To be sure, I’m not that good of a teacher!!
Thanks for looking,

Neal

Has anyone ever foregone sandblasting a restoration job and just done the "Sanding and Grinding" thing to get to the bare metal? If so, please let me know here.
Thanks,

Neal

I have foregone sandblasting on one restoration and used a combo of chemical spray paint remover and hand grinding with a spinning wire brush on a drill and a little bit of sanding. The pump was a G&B 176 and it was a lot of work. The end product always comes out the same, it is just a matter of how much manual labor you have time to put into your pumps.