rust

[LROBBINS]

A couple months ago I got fed up with having to re-make the 2mm wall stainless tube of the mount for Rachi's computer. It was just too soft, deformed within days and cracked within months. I replaced it with 3mm wall medium-carbon cold rolled high pressure pipe which held up nicely - until our week long vacation at the sea. Within a few hours, there was a brown patina (starting to look like Corten), and after a week, it was like this:

We got home this afternoon and I've removed the rust, first with stainless wire brush then with a non-woven abrasive wheel, and to protect it, at least for now, I brushed on a coat of high quality epoxy laminating resin that will cure overnight at 40o C. However, if any of you can suggest a better way to rust-protect this stuff, I'd like to know about it. Also, if you know of a source for high strength (not A2 or A4 or U.S. equivalents of those) stainless 16 ID, 22 OD tubing, I'd certainly consider replacing it.

This is a very simple mount. There is an upper collar fixed to the 16 mm tube to which the computer is attached and it interlocks with the lower tube that's clamped to the chair so that to turn the computer out of the way we merely lift and rotate, with a stop ledge partway, to bring it back front and center we just rotate back and it drops down, and to remove the whole shebang it just lifts off.

[Burgerman]

Zinc plate it.

Washing soda, water, vinagar, stir. Get a block of zinc off ebay you dont need much. Clean parts, use plastic container. Add about 3 to 9 volts and set current low, and agitate now and again. Then it wont rust. Tons of ways to plate against rust.

Copper sulfate works as does a copper pipe and some muriatic acid for copper plate. But its ugly.


This guys way is probably a bit more proffesional


youtu.be/Q8Xo43sfLgY

[rustyjames]

I don't know if they sell it in Europe but I just use Rustoleum in a rattle can, and don't even use the recommended primer. It's be working fine for me over the years. If it's something that sits outside I'll use a primer.

[Burgerman]

http://makeityours.co.uk/products/

They make many paints. I just sprayed a radiator with their radiator paint 3 weeks ago. Reasonably good and very white and supposed to stay white.

[rustyjames]

Well, you definitely have Rustoleum, quite a selection too. Interesting how much different the labeling is.

[expresso]

https://smile.amazon.com/gp/product/B00 ... UTF8&psc=1

this worked amazing for me - i used to use rustoleum all the time and it worked for short time - i tried primer - then paint etc, - in the end rust always popped up every now and then - this was for my PTA power toilet Aid - but finally since using the ZRC - its almost a year now and where its been treated - looks the same

will be doing the rest of the unit and re-coating again - it dries in Grey flat - which you can paint over - but have to be careful what kind of paint is used - it dosnt like alot of them - in the end - i didnt even bother painting over it - just left it as it is - this way i can even see it over time and can easily brush another coat if needed

a dremel was used to scrap as much off first - and just brush this on and thats it -

always damp and humid in the shower - the worst part was tackled and now the other side will be and other areas - once all the areas are done - i leave it grey and just brush over it - even once a year - but i feel this will last many years as it is already - since it easy to brush over it - wont wait many years - i make it a once a year think to keep it working -

[expresso]

before treated

[expresso]

after treated

[snaker]

There is an argument here about rust problem in cars. Many customers of Honda CRV found some parts in their new cars get rusty after just a couple of weeks using. Honda officially answered "NO PROBLEM" and they would not do anything to fix it. Personally, I think rust happens after short time using because Honda are cheating customers, they use low quality steel. Is it right? Or is it normal in all cars?

[Burgerman]

All steel rusts fast if it ever gets damp or wet. If the part is out of sight or heavy enough then rust not a problem. It has nothing to do with steel quality, just choice of material. Same reason I dont use steel bearings or bolts. And swap out for stainless steel. Stainless steel doesent rust.

How to stop steel rusting? Plate it with chrome, or copper, or zinc. Or use a different metal. Paint CAN work as long as its totally non porous, like the paint on modern cars - at least the 2 pack laquer they use over the base colour, and only if super clean, and zero rust underneath. You cannot paint over rust, as it just keeps on rusting away underneath regardless once started.

Those washers on the honda will outlive the car. They loo bad though. They should vave been zinc coated. Or so called passivated, or any number of electro coatings. But that costs.

[rustyjames]

For stuff that sits outdoors, and appearance isn't a factor here's what I use: https://www.fluid-film.com/automotive-applications/

It's a multipurpose product. It's got a weird smell though.

[Williamclark77]

If paint is not an option cold bluing is quite easy, cheap, and helps. I cold blue a lot of stuff pretty regularly. I buy selenium dioxide by the quart. It's not as affective as rust bluing or hot bluing, and like both processes, requires being lightly oiled on occasion.

Does the bar have to be hollow? If so, does it have to be hollow all the way through? If it doesn't have to be hollow completely through or only needs to be hollow 3 or so inches from each end (the depth I can do with a boring bar) I can send you one that'll never break. I make a lot of muzzle brakes from 416 stainless (https://wcmade.com/wcmade-products/Wc7701s-muzzle-brake) and have plenty of 1 inch 416 round bar that I could whittle one out of.

[rollingcowboy]

hey Will - I like the store!
next crazy idea I have I will use ya

[LROBBINS]

Thanks for all of the suggestions. Here's a summary of what I take from these.

(1) Various greases/waxes can be quite effective. The inside of this tube has a very thin coating of copper anti-seize paste and was not attacked at all by the sea air. However, I can't use these on the outside because it comes in contact with hands, legs, clothing etc.

(2) Barrier or Zn-loaded paints. I can't imagine that any of these would be more durable than the extremely hard and tenacious epoxy that I just used, and some of them are downright ugly. The epoxy will probably yellow with age, but at the moment it's just about invisible and on a test piece I can't dislodge it even with a chisel unless I heat it to >120o C.

(3) Electro plating with Zn sounds like a possibility, but that's a soft coating and would soon get well scratched up (though even scratched it would still protect from glavanic corrosion). It could be chromated (or cadmium plated if I had equipment to do that safely), but I think I would just coat with the epoxy after plating. Still, given how many rusted pieces of Zn plated nuts and bolts I have floating around, it will eventually rust.

(4) Cold blueing might work temporarily, but even black passivated steel eventually rusts in sea air (and, over a longer time span, even around the house).

(5) Will's offer of making a tube out of 416 stainless sounds like a truly ideal solution. If I could find a source here for less than 500 kg and use of a lathe, I would go right ahead and do that myself. But I don't, so I'd really like to take Will up on his offer.

The reason I'd do it myself if I could is that the 16mm ID is not exactly a precise measure as the 16 mm tube is welded A2 and has 2 90o bends in it so it is decidedly not round. Hence, I'll probably have to re-work the bore that Will makes as I did for the cold-rolled on the chair now. It was undersized, and I have neither a lathe nor a reamer that big, so I first used a 16 mm twist drill followed by carbide paper from 200 to 800 grit on the ID as well as using a Norton abrasive wheel to take out high spots on the OD of the inner tube until I got a tight slip fit. On top of cutting out the tapered stair-step interlock, all this took me a tedious 2 or 3 days. I'm sure Will can do better, if I give him close measurements, but some lapping may still be needed.

The mount is in two pieces: the upper piece is 40mm (1.6") long, the lower one is 140mm (5.5") long and both need to be thru bored, so the long one would need to be bored from both ends. Nearest I can tell with a caliper, the 16 mm tube is 16.0 at it's narrowest and 16.2 at its widest, so a bore of 16.2 -0/+0.1 would be pretty close. The short upper tube is a press fit and epoxied.

Will, is this a possibility for you? There's no rush and indeed this will be a backup for the current one for when (or if) the epoxy coating fails.

[rustyjames]

Will, congrats on the new business venture, I hope all your endeavors are fruitful!

[Burgerman]

rustyjames, you have a perfect name for this thread!

[Williamclark77]

Lenny, send me a sketch and where to ship it to. A picture of a hand sketch is fine. 416 machines fantastic but isn't as "stainless" as 304 and can be heat hardened a bit but can't be welded. I also have plenty of 1.25" 304 round bar leftover from a previous job if it requires welding.

hey Will - I like the store!
next crazy idea I have I will use ya

Holler any time. I don't charge anybody for stuff like this - within reason of course.

Will, congrats on the new business venture, I hope all your endeavors are fruitful!

Thanks! I need all of the luck I can get.

I had to do something with all of my free time! I had left my employer to recover from a surgery. I started this once I could get around again. I didn't plan on going back to work for someone but my previous employer made me an offer to return that I couldn't refuse. So, I'm doing both.

[rollingcowboy]

forgot to say - cute kid too!

[LROBBINS]

Thanks Will,

No welding required and I already know that 304 is sadly deficient for the durability of the interlock. 416 probably isn't as tough as the medium carbon cold rolled, but certainly a lot stronger than 304. I can also have it heat treated here, but that might not matter much for compressive strength and that is the only significant force involved. That it is less "stainless" doesn't bother me - we're not talking about repeated immersion in salt water. I'll make a sketch later today. It will include the "stair step" interlock, but if that's a PITA for you, I can do that with hacksaw, cutoff blade and file afterwards.

Ciao,
Lenny

[rustyjames]

rustyjames, you have a perfect name for this thread!

Indeed!

[LROBBINS]

Will,

a couple PMs are on their way to you

[Williamclark77]

Got it. Simple enough. I'll get to it within a few days. Thats better drawings than I get from Engineers for production parts. I won't harden it so it'll be easier to file fit and sand if needed. I highly suggest hardening. 416 is much more "stainless" after hardening, especially if polished, and will have strength nearer to medium carbon 41XX steels. It doesn't get very hard, around Rockwell C38 or so (don't quote me on that). I LOVE 416. It machines cleanly and is magnetic, which makes my life easier. I use magnets in place of proper working fingers.

304 and 316 are beautiful and extremely corrosion resistant, but absolutely suck to work with. They're very tough yet soft and work harden, making them very hard on tooling. I machined some 316 parts yesterday. I'll post pictures of the tooling afterwords when I get a chance.

forgot to say - cute kid too!

She gets it from me

[LROBBINS]

I haven't done much with 316, but I will certainly second your comments about machining 304 - before I got much more careful, I routinely broke taps when it work hardened, and it's not only soft, but creeps like plastics - there's no definite transition from elastic to plastic behavior. Yes, pretty, but with lots of negatives too.

I'll search up heat treating procedures for 416 so that I can tell the heat treating outfit what I want. If heat treated 416 is like normalized 4130 great; if like mildly heat treated 4130 even better.

[greybeard]

Pardon my ignorance, but what language are you guys using? 304, 316, 4130, 41XX
Sounds hellaver impressive. Just wish it meant something to me.

[Burgerman]

Different grades of stainless commonly available. Some are more corrosion resistant to others. Some machine easier.

E.G.

Which is better 304 or 316 stainless steel?
What's the difference between 304 and 316 stainless steel? The simple answer is 304 contains 18% chromium and 8% nickel while 316 contains 16% chromium, 10% nickel and 2% molybdenum. The molybdenum is added to help resist corrosion to chlorides (like sea water and de-icing salts).

Basically the more it resists oxidising, rust, corrsion, the more of a pig it is to machine or work...
But it doesent corrode easily. I threw a bit of polished stainless 304 tube outside my garage in 94 when racing bikes. If I pick it up today, wipe with a cloth, its still as shiny as new 24 years of rain and weather.

[Williamclark77]

I machined the od of both bars last night. I'll probably bore and finish them tonight.

Heat treating 416 is pretty easy, unlike other heat treatable stainless steels like S35VN. Heat to 1800 to 1850 degrees American (I don't know Celsius off of the top of my head) in an OXYGEN FREE environment. ie - either in an argon purged vacuum furnace, or much simpler, in a stainless steel foil pouch. Hold at that temperature for 30 minutes. Oil or air quench to room temp. Temper at 500ish degrees American for two hours. Remove from foil pouch. Polish. It will now have about the same physical properties as 4140 steel with very good corrosion resistance.

Without the foil pouch or argon purge oxygen will literally suck out a lot of and bond with the carbon on the surface of the material. Kind of like what happens when welding without shielding gas. It ain't pretty. Doesn't even make a good paperweight.

Working with 316 is about like 304. I've tried many cutting fluids. I found the absolute best thing to use when tapping is two stroke premix oil with the second best being dirty black used oil from my tractor (good old oil that still has sulfur and zinc in it). The two stroke premix worked better for me than $$$ tapping specific oils in stainless and copper. The nasty used motor oil seemed to work about the same or not quite as good as tapping fluid.

Quick video I did drilling/tapping the bar I use for the lockdown mechanism in my car that holds my chair in place. That's 316 stainless (only because I had a piece of scrap). Note that I peck drilled it to break the swarf vs steadily feeding through. A big no no in 304/316 stainless because the drill has to break through work hardened surface every time it restarts. This drill was shot and had to be resharpened after just four holes. It will literally do hundreds of holes just like this in 1018 mild steel or 416 stainless between sharpenings. Also note how the swarf stuck to the carbide spot drill. That sticky gumminess combined with its toughness is why it's so difficult.


youtu.be/e5qnnbISxAg

[Williamclark77]

And no, that's not my hand. That's my better 3/4. I got her to come hit the tap with oil so I wouldn't have to pause the video.

Pardon my ignorance, but what language are you guys using? 304, 316, 4130, 41XX
Sounds hellaver impressive. Just wish it meant something to me.

Nothing impressive. Every material has a name depending on usage. Metals, plastics, fabrics, paints, dyes, rubbers, etc. Most metals have a numerical or alphanumerical name to help distinguish their chemical composition. 416 is just a standard moniker for a certain chemical composition of steel. Same with 1018, 304, O1, D2, 4140, etc. Each has its strengths and weaknesses depending on what it's designed to do.

[LROBBINS]

What you shown for 316 is exactly my experience with 304. Cobalt bits do a bit better than HSS or Tn coated, but dull quickly - especially if one "bump" drills. A couple holes in 304 and I can't even use it on 6061. Work hardening combined with brinelling (that grabbing, seizing gumminess) will break small taps even if one's careful, and it's as likely to happen when backing off to break a chip as if one forces it in without breaking the chip. There's an advantage to 3-tap ISO metric hand tap sets - they not only have different tapers, but progressive diameters. It does mean that tapping every hole requires three passes, but there is less tendency to grab. Nevertheless, I have done in a number of 1st pass 3 and 4 mm taps. Getting a broken 3mm tap out of a blind hole is a disaster for me. I don't have an oil pump, but use drops of a cutting fluid for "difficult" metals that I bought from McMaster-Carr many years ago and use for both drilling and tapping. The bottle is so shop worn and filthy I can't even read the label now.

Thanks for the advice on heat treating 416. I will make sure to tell the shop to harden in an O2 free environment - they are an industrial shop and are used to doing that. 1800o F is 982o C and 500oF is 260o C. These match what I found using Google, except that tempering can be done pretty much in the whole range from 260o C (500 F) to a bit above 370o C (700 F) with little difference in the results, or at much higher temperatures for a soft result, but there's an intermediate range to be strictly avoided because the result is brittle. F to C is an easy translation. The hard one, where I have to very careful and have to look it up every time, is from English terminology to Italian as nearly the same words can have very different meanings. "Hardening" in English is "tempra" in Italian, whereas "temper" in English is "rinvenimento" in Italian, and there are a slew of specialized heat treatments that have very different names in the two languages. For example, surface hardening is "bonifica". Normalize is the same in both!

[Burgerman]

What you shown for 316 is exactly my experience with 304.

Whilst I know the difference, technically, in a simple home workshop I cant tell them apart. I use both interchangably in lathes and drills etc.

[Williamclark77]

I finally broke down and spent the money on every tap size I need in high quality taps in both spiral flute and spiral point versions. Some of the best money I ever spent. They've paid for themselves. I've only broke one in two or so years in hundreds of holes and that was in the bar in the video above. The very first hole I used water soluble drilling/tapping fluid. It galled and snapped retracting. I didn't even try to remove it. That tap is still in the bar as I use it every day.

I can't tell the difference in 304 and 316 manually machining. I think I can when CNCing 304 vs 316 though. The feeds and speeds for 304 are slightly too fast for 316. The same program works fine. Just turn it down 10-20% if it's having trouble. It could be in my mind though. I haven't ever done a direct comparison of identical parts in both.

This is what an expensive 2% cobalt hss drill looks like after peck drilling some holes in 316 a bit too fast (and that was less than 1/2 what I use for 416 and 1018) a few days ago. Powering straight through without stopping didn't do that, but the swarf was scary and could have caused issues. Perfect feeds and speeds with proper lube wouldn't do that but the drill still wouldn't last a very long time.