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Dealing with Extreme Surface Rust


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Let's pretend for a moment that we have an old rusty car that is worthy of restoration.   Say, maybe an old Reo like the one pictured below:

 

68c20bdc2ffa9f53908dcc161b8eb380--vintag

 

How would you deal with this level of rust?

 

Let's just focus on the hood.  What would you do to prepare the hood for paint?

 

My naive inexperienced thoughts are as follows:

 

1. Take a large wire brush on a power sander and wire brush all the loose surface rust off.

 

440b674f-0fe6-40c0-93da-1065d2dc9359_1.e

 

 

2. Then maybe go over the metal again with 80 grit sandpaper on a power sander: (only because I have a ton of 80 grit sandpaper)

 

f5133817-4b05-420f-8d73-1909f2b31ef9_1.0

 

 

3. Then clean the surface and wipe it down with the proper solvents and spray with primer.

 

From here we're home free.  We can just continue to clean up coats of primer until we're ready to apply a color coat.

 

How'd I do?  Did I flunk? ?

 

I'm just wondering how professional restorers would deal with this? 

 

Would you chemically remove the rust?

Would you chemically treat the surface before applying primer? ( I mean beyond the normal cleaning solvents)

 

If I did it my way would I end up with the thing rusting back out in short order?

 

I was actually thinking of sanding it all down with a 9" sanding disk of about 120 grit until I have all shiny bare metal showing.   But I'm wondering if that would compromise the thickness of the original metal?  And would that even be doable?  Would you actually get to shiny bare metal, or would you end up just sanding clear through to the other side?

 

Exactly how 'rust-free' does the surface need to be before moving on to primer?

 

Thanks in advance for revealing your professional secrets.

 

 

 

 

 

 

 

 

 

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Get it Sandblasted by a shop that knows what they are doing and then paint it with a couple of coats of epoxy primer.  This will hold it for as long as it takes to get to final paint stage as long as you don't leave it out in the weather.  

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13 minutes ago, DavidAU said:

Get it Sandblasted by a shop that knows what they are doing and then paint it with a couple of coats of epoxy primer.  This will hold it for as long as it takes to get to final paint stage as long as you don't leave it out in the weather.  

 

Exactly what David said.  Make sure the sand blaster has worked with cars, too much air pressure will warp the panels.

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Primer and sealer are two different things. So don't just use a "primer." PPG epoxy primer/sealer or similar epoxy or "2K" "sealer" on the bare metal, keeps any water/moisture from passing through. The PPG epoxy is non-sanding, you can't really sand it. You could then put a sandable primer over that.

 

What you use to wipe it down is different, wiping down bare metal vs a surface that still has paint on it. It gets wiped down with a "metal prep" which I think is a mild acid. I used to have some.

 

http://www.myrv14.com/buildlog/20160510/p-196_dplf_epoxy_primer-9-13.pdf   Data Sheet for epoxy primer/sealer

 

https://www.chemfil.ca/wp-content/uploads/TDS-DX-SERIES-METAL-TREATMENTS.pdf   metal cleaners identified

 

DX-520 Metal Conditioner is a phosphoric acid based coating chemical that will produce a zinc
phosphate coating on galvanized or steel surfaces. DX-520 Metal Conditioner contains a small
amount of detergent which aids in the removal of light soils and promotes the formation of a
uniform zinc phosphate coating. DX-520 Metal Conditioner is pale green in colour and may turn
darker over time.

 

DX-579 Metal Cleaner is a multi-purpose phosphoric acid based cleaner and pre-paint
conditioner for most metals. It can be used to deep clean a metal surface prior to paint or to
prepare a surface for a subsequent chemical coating. DX-579 Metal Cleaner is blue in color and
could lighten over time.

 

Edited by mike6024 (see edit history)
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The only way to deal with rust like that is media blasting.  I've tried the conversion coatings.  Suffice to say that I was unimpressed and if you plan to use any quality paint over them, well, good luck with that.

 

I've actually just had some recent experience with exactly this issue.  I have been skeptical of "dustless" blasting but I wanted to try it on a low-priority part.  I have a large compressor (24.5 SCFM) and an old TP Tools pressure pot blaster. I also saw a video of a rig where they used a simple water spray nozzle tie-wrapped to the blast nozzle. Figured I had nothing to lose so I tried it. Got a replacement sprayer wand and garden hose adapter from Tractor supply and rigged it up to my blast nozzle.  I'm using crushed glass media from Brut. Dialed the pressure down to under 50 psi. With the blast pot, I am able to regulate the flow of media as well as air, so I started with the media turned off and slowly increased media flow.  I ended up not using much flow.

 

I have to say, I was impressed.  It was slow going (mainly due to the configuration of the sheet metal part - it was the panel below the windshield with the slots for the heater air intake), but it completely removed heavy surface rust with no warping.  I was very careful to keep the nozzle at an angle and constantly moving. Yes, there is still heavy pitting, but the rust in the bottoms of the pits is gone. Yes, with plain water you get flash rusting.  It happened much more slowly than I expected, and it was very light.  You will want to go over the surface with a DA after blasting to smooth some of the pits, and this takes off the flash rust. Yes, it will require a skim coat of filler to fill the pits.  And finally, no, you cannot reuse the media, so it will get costly.  I've tried to think about ways to collect the media and filter it out of the water, but that's going to be tough.  Of course, you'd need to dry it before reuse.

 

All in all, this came out a lot better than I ever imagined.

Edited by joe_padavano (see edit history)
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Yep.  Needs to be media blasted to really remove that rust.  You will never get it all with that has been proposed.

 

I did my whole car with a compressor, a 5 gallon pot from Harbor Freight and media from a local equipment rental place.  Didn’t even need $100 worth to do the whole thing (you can reuse it several times).

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 Sorry, everybody failed this test.

 

 Submerge the hood in a bath of molasses and water (9 water-1 molasses) for about 2-3 weeks. Pressure wash it. blow it dry with air pressure and NO RUST, NO SCRUBBING.not even in the deepest pits!

 

 Buy molasses at a feed and grain store. $50 for a 5 gal pail.

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The molasses is a great way to deal with rust. Small parts especially.

But if there is any trace of paint or grease those areas wont be touched.

I would have it dipped.  Along with the doors, fenders, chassis, wheels, bumpers, etc. even the engine block.

All will come back as clean and shiny as one could imagine.

Edited by JACK M (see edit history)
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Wow, I'm really glad I asked!  Lots of good ideas here.

 

I figured there would be some suggestions for both chemically removing the rust, and for special epoxy type primers.

 

Sandblasting also sounds like it would be a lot less work than using a wire brush and sandpaper.   And it would do a far better job too.  I'll have to look into the sand blasting idea.  And then still use a special sealant primer after that.

 

I think if I went with my original proposal with incomplete rust removal and just spraying standard primer over that I'd probably have rust bubbling up from under the finished paint in no time.

 

So I'll look into methods for complete rust removal and then sealing that surface with a special sealant primer before applying the standard paint primer.

 

Thanks to everyone for the quick replies.

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2 hours ago, Roger Walling said:

 Sorry, everybody failed this test.

 

 Submerge the hood in a bath of molasses and water (9 water-1 molasses) for about 2-3 weeks. Pressure wash it. blow it dry with air pressure and NO RUST, NO SCRUBBING.not even in the deepest pits!

 

 Buy molasses at a feed and grain store. $50 for a 5 gal pail.

 

I never heard the molasses idea before.   I'll give this a shot on some small parts first just to see how it works.  If it does the trick I might think about using it on larger body parts.

 

I'm wondering if I could use a wet old blanket instead of a full tank bath?    Take the hood and saturate it with the molasses solution, then take a blanket and saturate the blanket too.  Then lay the wet blanket over the hood.  Come back a few weeks later and remove the wet blanket and wash the hood.   If that worked I wouldn't need a large tank to immerse the full hood into.  Plus, if this works it would make the molasses go much further too.   I guess I can try the blanket method on a small part and see how it goes.  That's the only way to find out.

 

 

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Dipping, either something similar to redi-strip or the molasses treatment is the way to go. Blasting can warp sheet metal and often leaves tiny ,deep particles of rust. Eventually they come back.

 That Reo looks like a gem, I hope someone saved it!

 

Greg in Canada

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Hello all the problem with rust is it’s hard to kill,the chemical strip weather it be molasses or electrolysis it will get in places you can’t see pinch 

welds are a perfect example, and after some time it will come out,I personally believe sand or media blasting is the best,also go to and automotive paint supply and buy a wand to get into places like inside the windshield pillars,use a spray them with primor or use a cavity wax,just my 2 cents,     Dave

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5 hours ago, Roger Walling said:

 Sorry, everybody failed this test.

 

 Submerge the hood in a bath of molasses and water (9 water-1 molasses) for about 2-3 weeks. Pressure wash it. blow it dry with air pressure and NO RUST, NO SCRUBBING.not even in the deepest pits!

 

 Buy molasses at a feed and grain store. $50 for a 5 gal pail.

YES!!!!!!!!!!!!!!!!!!! Check out all the successful molasses bath rust removals on the HAMB. No warpage, and clean metal. Bob 

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1 hour ago, 1937hd45 said:

YES!!!!!!!!!!!!!!!!!!! Check out all the successful molasses bath rust removals on the HAMB. No warpage, and clean metal. Bob 

Thats why they make plastic wading pools for kids.  Grandpa can make molasses baths then later use the pool for the woodgraining process (Float-on woodgraining)

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2 hours ago, 1937hd45 said:

YES!!!!!!!!!!!!!!!!!!! Check out all the successful molasses bath rust removals on the HAMB. No warpage, and clean metal. Bob 

 

Kind of hard to dip an entire unibody in molasses.  There was a guy on H.A.M.B. some years ago who scored a car-sized plastic container and dipped his entire 1958 Chrysler.  Oh, he also had a front end loader to move the items around...

 

Yeah, molasses will work... eventually.  I just would like to finish this project within my lifetime.  Media blasting it is. Done right, there is no warping.  There are multiple ways to skin this cat. Use what you're comfortable with. What's "best" for one situation is not necessarily best for another.

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Just another thought on the situation, if the car is one where spares might be had, is it better all around to seek a better hood, trunk, doors or fenders?  

 

Had a 47 Chevy coupe a long time ago, still think they are smartly styled cars, including the sedan without the quarter window like yours.  Hope it is coming along for you...

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Molasses will not touch paint, oil, grease etc. A few years ago I used some aluminum wire to suspend rusty parts in a 5 gal bucket of molasses mix. Checked on it  a few days later and found all items laying on the bottom and no aluminum wire. Checking for white metal before tossing a bunch of parts into a molasses bath may be a good idea. 

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22 minutes ago, Steve_Mack_CT said:

Just another thought on the situation, if the car is one where spares might be had, is it better all around to seek a better hood, trunk, doors or fenders?  

 

Had a 47 Chevy coupe a long time ago, still think they are smartly styled cars, including the sedan without the quarter window like yours.  Hope it is coming along for you...

 

Thanks.  My 47 Chevy is coming along just fine.  No serious rust problems on that car.   I just acquired a "newer" project car that everyone is trying to convince me to take directly to the scrap yard due to some serious rust issues.   I might actually end up doing that, but it never hurts to ask questions and learn new techniques along the way.

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10 minutes ago, mike6024 said:

What's the deal with molasses, does it become a mild acid?

 

I've been reading up on it and apparently it's actually phosphoric acid that is removing the rust.   Apparently molasses contains quite a bit of phosphoric acid.  You could probably just buy phosphoric acid and skip the molasses.

 

Edited to add.   I just read that phosphoric acid works best for rust removal when it's in a gel form.   The molasses apparently acts as the gel and therefore helps the phosphoric acid work better for this specific chemical reaction.   But you can probably buy phosphoric acid in a gel form too.

Edited by AntiqueCraftsman
Added information. (see edit history)
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2 hours ago, Steve_Mack_CT said:

Just another thought on the situation, if the car is one where spares might be had, is it better all around to seek a better hood, trunk, doors or fenders? 

 

If the car was one for which better sheet metal was easily available, we wouldn't be having this discussion.

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Joe that would seem to be the obvious answer but it would not be the first time someone decided replace vs. Restore makes sense after kicking options around, certainly for a 46 -48 Chevy that could make sense.  Craftsman did not specify,  so it was just a suggestion. ?

 

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I don't think molasses contains phosphoric acid. It is fed to cows because it contains a good mix if vitamins and minerals. It does contain chelating agents that grab the iron oxide molecules and bring them into solution, where they stay. Evapo-Rust works the same way, as does EDTA (which is used in some blood sample tubes).

 

Oxalic acid also acts as a chelating agent, as does citric acid. OA is better than CA, according to a web site I found with a chemist discussing them both for this job.

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3 hours ago, Steve_Mack_CT said:

Just another thought on the situation, if the car is one where spares might be had, is it better all around to seek a better hood, trunk, doors or fenders?  

 

 

Some folks like the challenge and satisfaction of restoration VS replacement. I once repaired a bic lighter. I was happy trying it but friends thought I was nuts!

Edited by JFranklin (see edit history)
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* Recent tests have shown that this process is NOT safe for Zinc Die Cast Metal, also known as "Pot Metal" Unless your goal is to dissolve the pot metal, do NOT immerse those parts in Molasses!!
It is not clear what other metals may also be affected by this process, so use caution.
Removing rust using Molasses uses a process known as Chelating. Without a good, scientific explanation, the process can be described as "Reverse Oxidation", wherein certain acids or chemicals in the molasses solution strip the oxygen from the Iron Oxide, leaving the iron behind. While I'm not absolutely positive about what exactly causes the rust to be removed, I am sure about one thing: It works.

The process is slow compared with other methods; electrolysis, various other acids, abrasives. Surface rust can be removed in a day or several, while heavy rust will require at least a couple of weeks. However, there are several advantages!

1. The ingredients are inexpensive. I purchased 5 gallons of feed-grade molasses from the grain elevator yesterday for less than $9, and that included a dollar for the container (because I didn't have one with me). This is enough to produce 20-50 gallons of solution (usually 1:4 or 1:10 is used).

2. There are no dangerous chemicals. Unlike some of the other methods, there is nothing that can burn your skin or eyes, and most other metals are unaffected, by this method.

3. There are no toxic by-products. The solution can be used repeatedly, for many months, but when it's time to dispose, you can safely pour out onto the lawn, where the molasses and water will decompose naturally.

4. It's effective. All oxidation will be completely removed, given enough time in the bath. The clean metal underneath will not be affected. For heavy rust it will take longer, and certainly a wire brush will help remove the large depsits, and help the process by allowing fresh molasses to come into contact with the rust.

Now, there are a couple of drawbacks. First, the process is slow. I've already mentioned that, but if you have more time than money, it's a great way to get rid of the rust on your restoration projects. Also, the Molasses solution smells like molasses. Even worse, once the solution starts to ferment, it will smell even more. I've tried using chlorine bleach to prevent fermentation and mold, but was unsuccessful. It's possible that the bleach evaporated out. I've read that people consider the fermentation process necessary for the process to work good, but I doubt that's the case. It will likely increase the acid level of the mix, but I expect the regular solution to still be very effective regardless. I may try the chemical that winemakers use to prevent fermentation in wines and see if that is effective.

Also, the parts will come out of the process with no protection from future rust, and the oxidation will commence again immediately. You must be prepared to clean the molasses from the parts, and protect the metal right away, either by painting, oiling, or or other means, otherwise your parts will quickly begin to rust again. I've soaked brake drums, heavy with rust for a couple of months (forgot about them) and after washing them with soap and water, they began to rust even before they were dry. Be ready to protect your parts!

Oh, and your parts must be degreased completely, since the solution does not cut grease, and the grease will prevent the solution from contacting the rust.

 

 

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This is a qut. panel that sat for 15 years unpainted and badly rusted  just like the original posted car ,that had soaked about two weeks. The bath was made out of 2- 2X10's cut to 6' and 4'. the liner was a piece of plastic  and covered so it would not evaporate.

DSCN2088 (3).JPG

DSCN2113.jpg

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Nothing beats sandblasting by a skilled operator. Quick, relatively inexpensive and thorough. And NO, sandblasting does not remove metal. It simply gets all the rust out of the pits. YES, it can warp if done by an inexperienced blaster. We have sandblasted everything from Model A wheels to Duesenberg body panels and have never warped anything. AND, the possible warping has nothing to do with the minor heat produced by blasting. It is the peening effect of all those thousands and millions of grains of blasting media that can caused a problem if not done correctly. We have a glass bead cabinet that just started its 40th year of being used at least several hours per week, sometimes much more, and the steel cabinet has not yet worn thru. Maybe in another 40 years. We use new sharp sandblasting sand for frames, wheels and suspension parts. As it breaks down into finer and finer dust we use it for body panels. When it has turned into fine powder it can even be used to remove paint from wood wheels without damaging the wood.

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Years ago I remember Naval Jelly. I haven't thought about it in years. Looks like the active ingredient in Naval Jelly is Phosphoric Acid. It was used a lot in the old days. Maybe it has gone by the wayside like creosote that we used on wood that was put in the ground. I can still smell that stuff just thinking about it. I suppose today it is considered a Hazardous material. Oh, wait, I see online that Naval Jelly is still available although it looks like it would be an expensive way to do a whole car. Not sure that it has the same punch as the old original stuff. Dandy Dave! 

Edited by Dandy Dave (see edit history)
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There are two features of the gel, or jelly approach.   One feature is that Phosphoric Acid supposedly works faster and more efficiently when in a gel form.  The other feature of the gel is that you can smear it onto the rusty surface and it will stick without the need to immerse the whole panel in a large tub bath.

 

I had the additional idea to use an old blanket to cover the gelled surface just to keep the gel from evaporating during the process.  I'm not sure if that's a good idea or not yet.  I might experiment on some small parts to see how well it works.

 

I'm thinking I might go out and get some molasses as well as a bottle of phosphoric acid.   Maybe mix in a little more phosphoric acid into the molasses just to give it a little more kick, using the molasses as the 'gel' base.   Then thin it just a bit to make it easily spreadable over the metal surface.   Finally cover the whole shebang with a wet blanket or cloth.   Then leave it set for a while and see what happens.   I think that's worth an experiment if nothing else.   If it works it will remove the need for large vats of large amounts of solution.

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I got a chuckle when I thought about the morass I might be letting myself in for by using molasses for rust removable. We live in the Cascade foothills, backed up against the Seattle water shed. We share our habitat with all sorts of fauna, some of which we seldom see. That is until we might be stupid enough to put out a bathtub full of molasses mix. Just use your imagination, I shouldn't have to draw you a picture.

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5 hours ago, AntiqueCraftsman said:

Maybe mix in a little more phosphoric acid into the molasses just to give it a little more kick, using the molasses as the 'gel' base.

Molasses is NOT phosphoric acid. It contains chemicals that act as chelating agents. You can't improve chelation by adding an acid that works in a completely different way.

Edited by Spinneyhill (see edit history)
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16 minutes ago, Spinneyhill said:

Molasses is NOT phosphoric acid. It contains chemicals that act as chelating agents. You can't improve chelation by adding an acid that works in a completely different way.

 

Thank you.  I stand corrected. 

 

DON"T add phosphoric acid to the mix!   As you say, it's a totally different type of chemical process.

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I am inclined to think that a molasses solution is a mild organic acid; until someone proves or demonstrates otherwise.

 

Coca Cola can clean things, and it is acidic. Anything below pH 7 is acidic.

 

(The average pH of Coca-Cola, Pepsi, and other colas is 3.4.) Carbonation combined with the acid can dissolve the metal oxides and remove tarnish from copper, brass and other metal alloys. Citric acid is known to remove the stains. Phosphoric acid is commonly used for rust removal

 

http://greencleaningproductsllc.com/mythbuster-science-of-cleaning-cleaning-with-coca-cola-effective-green-cleaning-products/

 

 

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What rust?  That's personality and history!

Leave it alone, it looks great and draws a crowd.   Look at that super rare California Top! 

Do only enough to make it safe, reliable, and comfortable.

Restore it?...it would be lost in an ocean or restored cars.  Original driving cars...they're rare baby, rare.

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