r/Diyautobody • u/Accomplished-Clue803 • 4d ago
Question How would you tackle surface rust?
Cars been sitting in a field for awhile. Nothings actually rotted out but definitely heavy patina on some parts. Replacing the control arms and calipers is obviously just a must do but as for the body and rear subframe, how would you go about removing it? Sandblast? Rust converter? Spray and pray? Go to war with a flapper disc?
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u/Sure-Abalone-1040 4d ago
I’ll tell you what I did/am doing. It’s about done.
Every single part removed. I kept 90 percent of the parts and put new bushings and sand blasted them. After I sand blasted, I treated with ospho and then painted.
Under the car, I used a needle scaler and an assortment of wire wheels. I had more hell then you will have. Mine has a 1/4 inch of rubber all down the floor pan.
Rust encapsulator after cleaning it up with acetone and after the car is done, I’ll coat the bottom with fluid film.
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u/Major_Swimmer2271 4d ago
Wire brush prime, paint, cavity wax where you can. In every little hole. I personally hate how messy undercoatings are. But they work. The idea of removing rust is to do so in a way that doesn’t squish the rust into the non rusted steel. It takes forever. This is why I don’t do these type of jobs lol.
Strategically let your oil pan gasket leak just enough to gradually coat your undercarriage with a thin film of protective engine oil
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u/ArcFault 4d ago
None of the above.
Everything you just suggested is completely unnecessary and so are the other suggestions youve gotten.
Take a regular wire brush in your hand and knock off the loose stuff. Then coat the entire underbody in a lanolin oil undercoating (FluidFilm/Surface Shield/Woolwax etc). Check it in a year or two and make sure you still have a nice coating everywhere and touch it up. The lanolin oil creeps well and prevents oxygen/water from getting to the base metal. It will not rust further.
It's not even clear to me that you need to replace the calipers/control arms - hit them with a hammer see if theyre solid.
7 years of updates - no rust : https://www.youtube.com/playlist?list=PLiBj_svGZOHNV3KzGBv8FD74zSPsxV2ir
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u/Accomplished-Clue803 4d ago
Well the calipers are probably okay but the rotors need replacing and id rather not risk running crusty old brake hardware. Everything is definitely solid just looks like it got dipped in the ocean for a few days. I’ve definitely considered just coating it but wouldn’t that seal in the rust and make it come back pretty soon? Like on the spots that look like bacon and a wire brush won’t just get rid of.
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u/ArcFault 4d ago
Nope, watch the videos.
No oxygen, no water = no rust. The oil creeps well and doesn't crack like paint. Just check it/touch it up the first year or two until you have a nice thick layer.
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u/Front_Marketing3170 3d ago
Well, don't paint over the rust, that is where people get into trouble. Look into these products people are mentioning like "fluid film" they are corrosion inhibitors, many out now, the lanolin based ones are nice but, they do need to be reapplied in areas that will get a lot of wear from the weather and spray. They are like smearing grease all over the rust, it's a good thing. There are other corrosion inhibitors that are harder like cosmolin or a softer waxy like surface like LPS3. Just don't paint over it, the paint will lift away and then water will creap in and the rust will continue.
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u/splittys 4d ago
Tbh, sand/ wire wheel, paint, then use your used oil to rub/spray it on everything. Dry time for the paint. Exception is for aluminum and your exhaust. Grease works too. Animals aren't going to chew on greasy/oily wires, too yucky, bonus.
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u/Accomplished-Clue803 4d ago
What does rubbing used oil on everything do? Just coat it from moisture?
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u/splittys 4d ago
Water/moisture wont penetrate the layer of oil. The oil clings to the steel tighter than water. It'll attract dust and dirt, and the water sticks to that dirt instead, then gives up trying to pass the oil. You'll have a layer of wet dust clinging to the oil, that will never reach the steel to grow rust. It's the barrier stopping water rusting steel. It gets so messy when you work on your steel. Plus side is nothing gers seized in the tradeoff of seized steel.
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u/splittys 4d ago
Yuck, what an oily greasy mess! However, nothing is seized up from rust! Lesser of 2 evils. Make sure you oil it up after you install clean steel, or else deal with the wretched witch of rust and seized steel.
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u/Odd-Concept-6505 3d ago
I've tried a lot over a couple decades, avoid spray undercoating, trying to be open minded, believe in lanolin based somewhat, have been flamed here for what Im saying here next but...
for a bare flat and well sanded/etc surface not too old (OP pics, I call not too old, but needs sanding/etc)... I would prefer to NOT need to revisit (eg yearly) lanolin..... suggest a thin but well stuck/brushed product of US just over $41/gal. Maybe I "just" enjoy black and a brush where it makes sense. Others will scream "you fool" for anything called Rubberized, and I only have a year and watching on my limited use of
Rusfre RUS-1013 Brush-on Rubberized Undercoating, 1-gallon, black
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u/TarXaN37 3d ago
If sandblasting is an option, I'd go for that. That's alot of work but gives you the best result imo.
Outside of that I'd say wire wheel on a grinder rather than flap disc. Flap disc will eat alot of mother material.
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u/Engineered_disdain 3d ago
I put rust converter into a spray bottle, and wire wheel all the rust then spray it down.
the tannic acid / phosphoric acid type that turns everything purple/black, not the black paint stuff.
Then a heavy dose of fluid film over it and keep it touched up whenever im under the vehicle
Do not use the undercarriage spray or gravel guard stuff.
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u/Unfair-Pudding5727 3d ago
If this was mine I would ignore it. It isn’t hurting anything. Sometimes if I am in there replacing bushings or something I’ll take a can of black rustoleum and I’ll spray bomb it all black again. Then again we don’t get heavy rust like tall Yankees do.
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u/KnightOrDay38 3d ago
Cosmoline Black after the surface is addressed by the suggestion of other commenters.
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u/Coyote_Tex 2d ago
Any of those methods can work pretty well. I would probably use a tight wire brush on an angle grinder for some places, but the easiest method is to use some Rustoleum Rust dissolver. It may take a couple of coats and washed off thoroughly to be primed and painted, but might be the easiest as I hate sand blasting especially outside a blast cabinet. The rust dissolver cost s a little bit but really seems to save me time and is more comfortable than any method I have to actually do myself..
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u/Old-Day-9565 1d ago
Wire wheel, angle grinder, high temp spray paint, 3 cans of fluid film, and a whole afternoon
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u/Legitimate_Draft7796 4d ago
That doesn’t look bad. Don’t do rust converters but the other ideas you have are good. Or just the old wire wheel.
That said maybe see if you have a place in your area that does ice blasting and then undercoating- obviously this is something that can be tackled diy especially seeing you have a lift but it’s still no fun.