Is it true that rust is like a cancer, and if it is present it helps further the development of more rust, or is it just a folk myth?
I'm trying to decide if I should go through the hassle of taking a wire wheel to some of the more seriously rusted parts on an old but good bandsaw, or just spraying down the rust with oil and calling it a day.
You've never had a car in a northern coastal region have you?
>>947864
Its true. The problem is two fold. Rust cause the metal to flake up and increases surface area. That allows more moisture to get near the metal and cause more rust. Moisture also gets between the layers of the rust and doesn't evaporate as quickly, causing even more rust. It also gets under any paint or coating (like chrome) that is protecting the metal. The coating flakes off and more metal is exposed to the air to get rusty. The oil will help but its best to remove the rust and protect it with paint or a wax for working surfaces (like the table of a bandsaw). You don't want to use an oil on the working surfaces because it can stain the wood and discolor it or cause problems with finishes. For non-working surfaces, the bed of a lathe for example, oil is fine because the wood wont touch areas.
Rust does breed more rust.
If your bandsaw can be disassembled easily...you might consider abrasive blasting or soda blasting the metal pieces.
I work in the steel industry and see all sorts of rust removal, with wire brushing being the most labor intensive.
If the rust is severe, disassemble and blast it.
If it is manageable, then a rust eating chemical works great with a brush.
>>947866
I'm from the Midwest. I only worry what the rock salt does to the car's undercarriage.
>>947864
how do you think bridges stay up? think they have a little man running around checking for tiny scratches and he quickly buffs them down then applies three coats?
no. when people talk about rust being cancer they're talking about a used shitter they bought that some faggot did a shit paint job. so when it finally shows through and starts flaking up after 6 months people go ahh, shit my car is going to flake apart into pieces now. no its just faggots bogging up the frame and painting it shittily to sell.
now there are very effective treatments for mild steel like a fucking sacrificial anode. like zinc. comes in paint form so you can just spray it right over the top.
>>947881
not op, so you cant use normal spray paint over rust to halt the rust from spreading? and what can i use to make rust fall off without weakening the steel... i should prob google this shit
>>947884
you can use phosphoric acid. although sanding back to bare metal is prefered. there are also corosion inhibiting paint. dulux makes one called rustguard. also google cold galvanization
>>947887
thanks anon! much appreciated
>>947864
In theory, no rust is not like a cancer. because if you remove moisture. the rust stops. what rust is tho is hygroscopic. basically it holds water, allowing the metal under the rust, to also turn into rust. so in that way, yeah its sorta like a cancer. it will keep going.
>>947894
>>947864
>>947868
So yeah, wire wheel WON'T remove all the rust, it will remove all the rust that easily flakes off and may have moisture pockets underneath it. Also, rust that can flake of will shift and generally crack the paint slightly, and then, because it is hygroscopic, will absorb ambient moisture and deliver it to the nearby metal.
Naval jelly is a chemical that reverses the rust process, and turns some of the rust back into good metal.
If rust is like cancer, oil is like chemo... without surgery, chemo will just slow it down if it's big. If it's tiny spots, chemo will work well, but if it's like, rust textured rust flakes, then yeah, wire brush all the easy flakes, naval jelly on the surface rust, oil or paint or w/e to keep it from reemerging.
Oh, and also, water is a CATALYST for steel rusting. It does NOT GET USED UP. So if you trap water in there, and the seal isn't good enough to keep air from it, it will get oxygen, moisture will catalyze oxidation, and moisture will remain present. It'll just slow down because limited moisture and limited oxygen.
>>947881
If that dirty jobs program is any indication of how to maintain a bridge. Aparently the best method is to paint them and paint them and never stop painting until half the bridges weight is in paint and then paint it some more and don't forget to paint it again before you paint it one more time and then keep painting.
The rust being hygroscopic makes sense. But oil, which easily penetrates rust, should be able to wick right through the rust and coat the underlying iron, eh?
What are your thoughts on those rust-converting primers? What is the chemical process behind them? As you can tell, I really want to avoid having to take this machine apart despite all the rust.
Yes it's true, run an electrolysis bath to remove it. Pic related I'm currently removing some rust from an old bench I'm restoring. I'll post a thread about it later as I get further into completion.
>>947994
After several hours I used a wire brush to brush off the rust so it would expose the surface more. You can see the difference here. It was just like powder sitting on top so I just kind of brushed the surface and it came right up.
>>947997
Here's a before picture, covered in rust
>>947881
>how do you think bridges stay up?
Sometimes they don't.
>>948003
The I35W Mississippi River Bridge...
- 1990: declared "structurally deficient" due to corrosion.
- 2001: cracks and "out-of-plane distortion" found in the girders. The cracks were drilled to stop them from expanding.
- 2005: declared "structurally deficient" once again. Repairs were planned.
- Jan 2007: Those repairs were cancelled fearing the bridge could not withstand the construction process. Internal documents cited the possibility of collapse, and considered condemning the bridge.
- Aug 2007: despite all of the above, the pavement was resurfaced. With almost 300 tons of equipment and supplies on the bridge, the bridge collapsed.
>>947864
"Fool," said I, "you do not know
corrosion like a cancer grows."
>>948003
Yeah, but now we have a new and much nicer bridge and a nice memorial. Not to mention the light news about small business owners who survived the collapse.
>>947881
Actually I know a few people who make a living as bridge inspectors, they once over a bridge every year and mark everything to be repainted.
>>947864
>Is it true that rust is like a cancer, and if it is present it helps further the development of more rust, or is it just a folk myth?
rust doesn't cause more rust, but it does begin to form on a microscopic level...
so while you may clean off all the rust you can see, there is still more forming that you could not see.
as for the bandsaw, I would wipe it with some heavy oil and call it a day
your time would be better spend remedying the cause of the rust, if possible (--that is, remove nearby sources of humidity, or install a dehumidifier--)
>>947994
Hey machete guy, any reason why you chose to go with electrolysis bath specifically for that job?
I've read about how to setup those baths, but haven't found much reasoning for choosing that over a cheap acidic method, like Citric Acid. I've also had pretty decent results with a 50/50 mixture of white vinegar and water, which is great since I can gallons of both for only a few bucks. Typically 3 to 4 hours has pretty decent results, longer for heavier rust. Thoughts?
technically rust as a rust inhibitor.
rust, iron oxide forms a surface which prevents further oxidation by covering bare metal. In that way, there's 2000+ year-old iron pillars in india which have an even layer of iron oxide over the surface, and thus, have not corroded further.
technically, however, is not the same as reality, outside of controlled environments.
Rust, iron oxide, is less dense than iron. it therefore expands, taking up a larger volume. that expansion means it causes flaking, which exposes more steel to oxygen. in cold wet climates, water soaking into rust can freeze and flake off the rust, resulting in more corrosion - cold but dry does preserve quite well however.
the other thing is surface area. a polished surface rusts slower than a rough one.
>>948402
The iron pillar you're referencing is the Iron Pillar of Delhi, and it's still standing because of a layer of Iron Phosphate, not because the 'rust protects the rest of the metal'.
I'll give you that a form of iron oxide, Iron Oxide (II, III), otherwise known as magnetite, protects iron from corrosion, but your implication that the Iron Pillar of Delhi is rustproof because rust inhibits rust is utterly wrong.
>>948398
Sounds good, I needed to try something and this is what I could think of. Found the process on YouTube. For the machete I just did a wire brush and psalm sander since it's flat. But this bench has intricate patterns so I had to try something else. You know the damn thing is, no matter how you do it you still have to wire brush it when you're done to remove the black crap. But, at least this way the rust gets removed from the pits. I need it to be 100% rust free since I will be painting it when I'm done.
>>948402
>>948436
that is true for IRON, but NOT steel. if it's is wrought iron, iron oxide can form a protective film layer on the surface which slows down the rust process immensely. It will still eventually rust through though. The impurities that make steel steel tend to contribute to the constant flaking off and pitting of the surface layer, constantly exposing fresh metal to rust.
I'm not sure exactly why, it may have to do with the higher ductility of wrought iron, so that it will flex to accommodate the expansion of the oxide.
Also, for older pieces of iron, it was pretty much impossible to purify it because metallurgy didn't exist in the way it does now, so could be contaminated with chromium etc.
>>948578
I was literally thinking the same thing yesterday as I was hitting it with the wire brush. Sand blasting would have definitely been the best/fastest way to go in this case. Especially since cast iron surfaces are already a little bumpy. I wanted so bad to go to harbor freight and get a cheap sand blasting kit, but it's not really something I'd see myself using in the future. Plus it would take up more room in my garage just sitting around when I'm done with it. In the end I went to home depot and bought a Dewalt corded hammer drill and used that. It was about $100 bucks and I'll get plenty of use from a corded drill in the future, plus I can store it in my tool box when I'm done. The hammer setting is nice too for when I have to drill through concrete. I've done it before hanging garden hose holders to the brick and it's a pita and was really taxing on my cordless drill. I have a Craftsman one and it's the tits, but for this project the battery kept dying because I had so much surface to wire brush.
Side note, I ALMOST bought the Makita one for the same price because that's supposed to be a really good brand. Fortunately I checked the reviews before buying and both Makita options had poor ratings. Apparently the chucks are not great. The Dewalt had a shitload of good ratings so clearly a lot of people purchased it and it works really well, who knew.
>>948000
>covered in rust
looks like copper in the pic
>>947955
>It does NOT GET USED UP.
Not true. Rust is not only oxides of iron, it's also hydroxides. Some water does get "used up".
>>948578
Not him, but antiques restorers electrolysis because it's the least destructive and most thorough method of rust removal - doesn't abrade, etch, or corrode the underlying metal at all, and is a self-limiting process. Once there is no more rust to detach from the iron the process stops for all intents and purposes. Sandblasting hides the appearance of pitting because it's abrasive.
Nice bait Op yes rust ruins metal and it falls apart or holes get in it or degrades
