View Full Version : Stripping rust and paint
03-21-2004, 09:24 PM
This topic seemed to be taking over in the "how to fix panel" discussion, so I thought I would start a new discussion here.I got some different ideas but what I really want to know is what chemicals will strip rust the way places like redi-strip do?Any ideas on different methods of stripping panels with heavy surface rust? Greg
03-21-2004, 09:33 PM
there was some discussion on the Hobart forum many months back about using some sort of electrolisis to strip heavy rust. I think it involved using an old lawnmower blade, a battery charger, water mixed with baking soda and a sheet of graphite. Some of the pictures posted were amazing.
Another thought, rather than stripping the rust, because you are removing material is to hit it with phosphoric acid. that turns out fairly well.
03-22-2004, 04:55 AM
Actually is Arm & Hammer WASHING soda. Not baking soda. It does work very well I might add.
See this link http://antique-engines.com/electrol.asp
It will explain things very well.
03-22-2004, 08:20 AM
While the electrolytic process isn't practical for large pieces, I've used it several times for smaller parts up to a 15" diameter hand wheel I use on my bead roller. Also used it on some small hand tools and even a set of starret micrometers I bought at a garage sale for a buck. :lol:
You can use baking soda or washing soda, they're the same product with different purities. Washing soda is cheaper. I used a small 10 amp charger and a large Rubbermaid tub. I imagine you could use a wading pool for something large. Amazing process. Takes a while, so don't plan on watching it. My hand wheel was flakey black rusted cast iron. Wire brushed it every few hours. Took about 2 days total with minimal work. Results were great. :o
The electrolytic rust removal process tends to be a 'line of sight' process between the anode and the cathode. I can never remember which is which, but the piece you want stripped is one, and you use another piece of metal as the other. I have heard of folks using a wire mesh to line their (non conductive) tank/container/etc in order to surround the workpiece.
It has also been suggested that you use a piece of stainless steel for the sacrificial 'terminal'. Old cooking pot lids is a good source for this. Plastic garbage cans make convenient tanks, though even a large impromptu bladder of Visqueen will work so long as you support it to hold in the electrolyte, and don't puncture it. The vile nasty byproduct of the process is not supposed to be a hazardous waste material, and might even be good for some plantings. If not<G>, maybe it'd kill the weeds in your gravel driveway. IDK.
There has been talk about molasses in solution working to remove rust, much like acid, and apparently it is very benign, and inexpensive to boot if you can find the right sources.
A Google search on rust removal and electrolysis should uncover volumes of info long since posted on the web. A garbage can, baking soda, water, and a battery charger, plus the right knowledge will do remarkable things. Any material 'lost' in the process is already oxidized base metal and is lost in any case. Acid on the other hand will remove rust and sound base metal, and in some circumstances damage the base metal, as well. DAMHIKT.
Electrolysis really is an easy and satisfying way to reclaim lots of things otherwise ruined by rust. I like sandblasting, too, but that's another matter altogether. Rust never rests!...
03-22-2004, 02:11 PM
I'm not exactly well versed on rust removal, but I have played around with a couple of different things. In using a mild acid like phosphoric acid, it didn't appear to remove any base metal.
I was told that it actually works with the rust to form an inert byproduct...can't remember the name, something phosphate...
Then there's the stuff from Por-15---metal prep, that does a zinc coating. Por-15 works fairly well from what I've seen. Again I wouldn't say it's really rust removal, but another means of combating rust.
Hi, Ken. Yeah, I've used some stuff called Ospho, which had phosphoric acid in it, I think. I do believe it'll take away base metal, but not much if used sparingly, I think...
The other stuff you mentioned seems to form a coating on the surface of the metal, which is actually a combination of the metal and the product, but I've never liked it much and have used it hardly at all.
I tried to rescue an infeed table on a jointer that had been badly rusted by some calcium chloride leaking onto it from above. Very corrosive and unfriendly stuff. But I didn't care for the resultant coating--not uniform, too thick, just not what a finely finished surface needs to be.
03-22-2004, 04:23 PM
I'm not sure what's in Ospho. I purchased a few bottles of floor etch which was pure phosphoric acid and I didn't add water. I hit the metal and it kind of had a baking soda/vinegar affect to it.
Phosphoric acid is very mild...so much so that it can be found as the 5th ingredient in Coke. :D
Hi, i personally use muriatic acid dip for quite long time and found a process that work pretty good.first your acid must be dilute ,the hardware store kind is already 20% but you must go another 1 to 5 ratio. So 1 gallon acid for 5 gallon water,.Dip your part and check it every 30 minute or less ,rinse it with garden hose. You will see rust running off.repeat until it's clean or only some rust spot.
The problem is acid eat metal at same rate of rust and if your part it's not rusted equal you will loose some metal before it's totaly clean.You could help those spot by wire brush or sand blast.After your part is derusted and rinsed, you must neutralize with base , specially cast iron parts because they are porous.I use lime from garden store , i paid 3 $ for 40lbs bag dilute in water(45 gallon), You could leave your part in this solution as long you want,metal don't rust in basic solution.Once you get it out and let it dry ,it will flash rust again ,i rub the part with cheap metal prep from hardware store, most if not all contain phosphoric acid which attack rust and leave a phosphate finish.Your part will be protected for couple days and ready to prime/paint.The solution is good for as long you need it and should be dispose in proper facility.It could be reduce by boiling to remove water.Try it with none valuable part first,to get use to it.
Very important ,leave your container outside ,because the vapor from acid will rust everything in your shop,i learn it the hard way.
03-24-2004, 08:02 PM
For a cheap and easy paint removal, hot lye solution.
i have a metal tank and a water heater element(heavy duty
works in mud, standard ones last a year or so)
i only set the temp controller for 120 degrees, dirty/greasey
stuff can be cleaned also.
Not for aluminum or pot metal(zinc)
always wear rubber gloves and a face sheild. rinse the parts
Phosphoric acid is the main ingrediant in metal prep, rust mort
is one brand we can get locally.
BRENT in 10-uh-C
05-30-2004, 06:00 AM
Let me ask this, do you think if the water solution in the electrolysis tank was heated that it would quicken the rust removal process?
The reason I ask is that the company that I use to pickel (de-rust) metal car bodies has a tank that is heated. I have no idea what chemicals are in their tank but I do know that the solution is heated to 150 degrees. For small(er) parts they charge about $100 a piece. Since there is usually 4 or 5 smaller pieces involved in each load I take, I could affort to spend a little to build something to use in-house.
Maybe some sort of 'stock tank' used for watering livestock with a couple of metal plates attched to the side to hold hot water heater elements could be used.
05-30-2004, 10:24 AM
The previous are really interesting, I have some A-arms I think I'll try this process on, but what if you have a car that was stripped to bare steel, primered and stored outside? The primer is porous, has absorbed water and most of the body is covered by surface rust scale. I don't want to sand blast (if possible), I can straighten the panels if warped but you will never be able to remove all of the sand, it tends to screw up a perfectly good paint job. Any suggestions?
Thanks all, Phil Gilmore (rookie)
p.s. We have at least 3 Phils now, thought I should differentiate. :wink:
06-16-2004, 09:08 PM
Here's a link that has an example and pictures of using electrolysis to remove rust
BRENT in 10-uh-C, I'm relying on an all too frail memory, here, but I believe the Redi-Strip process uses a basic solution that is heated. How basic, and how hot, I can't say. The value is it does not remove any parent metal, like acid can.
I don't think they use any electrolysis with their system, but can't say if heat would help or hinder the electrolytic process. It is essentially a plating/de-plating process, and heat may help, but I'd try without heat first--you'll probably be gratified by the results. At $100 per item you can invest in a pretty substantial system and still get a quick ROI. I've not heard of anyone trying it, but I'd look into the EPDM (EDPM?) rubber membrane used in roofing as a 'tank liner' for a larger tank installation.
A couple of reminders: it is a 'line of sight' process and so surrounding the rusty workpiece with a mesh or similar terminal will help get all the rust all over the piece. Also, be sure to entirely immerse the workpiece, to avoid leaving marks at the water level lines, and possible damage to the metal at that point, as well. Do the Google search on electrolytic rust removal or similar. There really is a lot of good info out there. Good luck.
I want to thank you for sharing your experience building and using a powder coating oven using an old electric range. It was particularly clever and encouraging. Best wishes...
09-23-2005, 01:29 PM
I am attaching a photo that show the progress (or really lack of it) trying to remove rust from some square tube I used to build a car rotisserie.
I have another sample running the the electrolysis method. Seems to work very well now that I know not to use too much laundry soda. Also very slow.
However, the photo shows the rust, a section that was sand blasted and a small section that was wire burshed / sanded.
Any suggestions as to skills, method, equipment, supplies would be greatl appreciated. I do not want to have someone else do this. I want to improve my skills, methods etc.
09-23-2005, 02:25 PM
The heat speeds up the chemical reaction in the case of the acid being used on your car body. Adam
vBulletin® v3.8.6, Copyright ©2000-2013, Jelsoft Enterprises Ltd.