It is currently Mon Dec 18, 2017 5:14 pm

 

Stainless rusting...

Share tips and tricks you know of in this forum. Plasma cutting, material handling, metal finishing, marketing, or anything that you feel is helpful.
davek0974
Posts: 736
Joined: Wed Aug 13, 2014 8:30 am
Location: Hertfordshire, England
Contact:

Stainless rusting...

Postby davek0974 » Wed Jun 14, 2017 10:20 am

Ok, so I have been making plaques from stainless for a few years now, no complaints so this question may be needless but i like to learn ;)

I read that if you work cut stainless with tools - wire brushes, files, saws etc that been used to cut carbon steel, the stainless will rust.

What i currently do is plasma cut the plaque from brushed stainless 1.2mm sheet, clean up edges on the belt sander (used for carbon steel too), hit the back side (unseen when fitted) with a cup brush (used on carbon steel) which gets rid of any dross, then hit the front with a rotary flap drum (not used for steel) and finish with a final working with scotchbrite - the front working is always done in line with the brushing.

When working the front i work on a clean wood pad so no crud is dragged up from the steel bench.

What i am slightly concerned about is rusting - people tend to view stainless as rustless so although i have not had a complaint yet, i also don't want any in the future.

I have also read that if the stainless is brushed up clean it will re-passivate and not rust or i could soak in Nitric but i really don't want to go there if possible.

Any thoughts???

User avatar
exapprentice
Posts: 340
Joined: Mon Jul 06, 2015 1:57 pm
Location: Wiltshire, UK

Re: Stainless rusting...

Postby exapprentice » Wed Jun 14, 2017 10:40 am

Hi Dave

Hope all is well

I believe the only grade of St/Steel that will not show sign of rusting (due to the metelergy) is 316 which is truly austenetic whereas you can can some st/steels that are martensitic and will eventually show signs of rusting?

Maybe I am wrong but I am sure that some fellow members will add in?

"The austenitic/higher chromium stainless steels, usually required in very high or very low temperatures, are generally more corrosion resistant than the lower chromium ferritic or martensitic stainlesses"

try gogging "will st/st rust"? ;)
Best Regards to all
Exapprentice :D
(Pete)
10'x5' DIY table / PM 45XP + M/C Torch - Trying to add 4 axis Tube cutting :(
Linux/CommandCandCNC MP3600 / PN200 / DCP-01 / PWM
Solid Edge, Inkscape, SheetCam, Scananything & Andonstar USB Microscope

User avatar
_Ogre
Posts: 529
Joined: Sun Sep 15, 2013 4:26 pm
Location: Motown

Re: Stainless rusting...

Postby _Ogre » Wed Jun 14, 2017 12:21 pm

davek0974 wrote:I read that if you work cut stainless with tools - wire brushes, files, saws etc that been used to cut carbon steel, the stainless will rust.

this is true, though it probably doesn't pertain to your usage

when i did pharmaceutical grade stainless piping we had to be concerned about cross contamination with carbon or ss
particles of carbon steel can stick to grinders and get embedded in the ss, only the carbon particle stuck in the ss will rust
we had grinders, files and tools marked for ss only

now i work with hotrodeutical grade stainless exhaust systems and we don't worry about cross contamination :mrgreen:
there are different types of stainless with varying amounts of nickle, chromium and other metals in the mix
304 and 316 are pretty much rust proof, 409 is what most oem exhaust systems are made with, 409 will surface rust and seal itself from further rusting


from the internet:
304 contains 18% chromium and 8% nickel
316 contains 16% chromium, 10% nickel and 2% molybdenum. The molybdenum is added to help resist corrosion to chlorides (salt)
T409 has a chromium content of 10.50% to 11.75% while its nickel content is only 0.50%
bulltear 4x8 cnc plasma table, candcnc bladerunner w/dthc, hypertherm powermax 65, sheetcam, mach3
laser cross hair for hypertherm torch http://www.plasmaspider.com/viewtopic.php?f=6&t=12508
an ogre smiley :mrgreen: how cool!

davek0974
Posts: 736
Joined: Wed Aug 13, 2014 8:30 am
Location: Hertfordshire, England
Contact:

Re: Stainless rusting...

Postby davek0974 » Wed Jun 14, 2017 2:17 pm

Thanks guys,

The stuff i currently have is 304 grade, it seemed the best all-round back when i got it.

Good to know it should be ok, my main concern having read the data again is those customers by the coast but as i said, i have had no issues yet in over 5 years so fingers crossed...

Maybe on the next order i'll go to 316 grade if they do it in brushed finish.

Also, incase anyone's interested i have found a good cut recipe:-

Hypertherm PM45, 30A consumables at 30A, whatever cut speed suits your machine, 3mm perpendicular lead-in, no lead-out, add 0.5mm over-burn and a path rule to kill the torch 1mm before the end - works lovely. ;) ;)

DXF
Elite Contributing Member
Elite Contributing Member
Posts: 1314
Joined: Tue Feb 22, 2011 5:15 pm
Location: Mountain City, Tennessee

Re: Stainless rusting...

Postby DXF » Thu Jun 15, 2017 12:03 pm

Here are 2 pics of a front tag I cut from 304 stainless steel a few years ago. I could not figure out why it was rusting until reading on this forum that using the same grinding discs on carbon steel and stainless steel will penetrate the stainless steel and cause this. I have since stopped using the same grinding discs on both steels and no problem. Also, if you cut a hanging stainless steel piece and use a galvanized "s" hook to hang it from.....when the s hook wears thru the galvanizing it will cause the stainless steel to rust where it rubbed against it. Anyone know where to buy stainless steel "s" hooks?

Dave Hanks

You do not have access to download this dxf file.
Become a Contributing Member to gain access to the thousands of files shared by our members. Click Here


davek0974
Posts: 736
Joined: Wed Aug 13, 2014 8:30 am
Location: Hertfordshire, England
Contact:

Re: Stainless rusting...

Postby davek0974 » Thu Jun 15, 2017 1:17 pm

Yes that matches the front door number I made for our own house (test piece) in fact ours is a bit worse than that. I'll have to get it down and buff it up again.

I have since tried to separate the tools used where possible so hopefully that will help.

User avatar
SeanP
Elite Contributing Member
Elite Contributing Member
Posts: 727
Joined: Thu Aug 01, 2013 11:50 am
Location: Co Kerry, Ireland

Re: Stainless rusting...

Postby SeanP » Thu Jun 15, 2017 5:41 pm

davek0974 wrote:
Also, incase anyone's interested i have found a good cut recipe:-

Hypertherm PM45, 30A consumables at 30A, whatever cut speed suits your machine, 3mm perpendicular lead-in, no lead-out, add 0.5mm over-burn and a path rule to kill the torch 1mm before the end - works lovely. ;) ;)


Will remember that one Dave thanks, are you on genuine 30a parts or have you found any decent alternatives? the ones I got from plasmatec are horrendous, slipped up there, no probs with 45a ones though.
Powermax 45XP
Home built table, Candcnc DTHC 2, Dragoncut 620-4
R-Tech 210 Tig, Jasic 250 mig
Sheetcam, Scanything, Coreldraw X8, Solidworks
Table build gallery

davek0974
Posts: 736
Joined: Wed Aug 13, 2014 8:30 am
Location: Hertfordshire, England
Contact:

Re: Stainless rusting...

Postby davek0974 » Fri Jun 16, 2017 2:12 am

Yeah i've gone back to genuine all round, too many other possibilities for trouble so i thought it best to stick with known parts, never tried the plasmatic 30A as i don't use many but the 45A ones didn't seem to last quite as long as genuine.
:)

bhamer62
Elite Contributing Member
Elite Contributing Member
Posts: 282
Joined: Mon Sep 10, 2012 8:06 pm
Location: Columbia, PA
Contact:

Re: Stainless rusting...

Postby bhamer62 » Fri Jun 16, 2017 3:13 pm

Mr Hanks, McMaster Carr has SS S hooks https://www.mcmaster.com/#stainless-ste ... s/=183i73p
Also, when you weld or cut SS the heat can locally burn the nickel content out of the steel in the area of direct contact allowing it to rust....Pharmaceutical and food grade items are sometimes passivated as a secondary operation after cutting or machining to eliminate this, but it is costly.....

DXF
Elite Contributing Member
Elite Contributing Member
Posts: 1314
Joined: Tue Feb 22, 2011 5:15 pm
Location: Mountain City, Tennessee

Re: Stainless rusting...

Postby DXF » Sat Jun 17, 2017 1:31 pm

bhamer62 wrote:Mr Hanks, McMaster Carr has SS S hooks https://www.mcmaster.com/#stainless-ste ... s/=183i73p
Also, when you weld or cut SS the heat can locally burn the nickel content out of the steel in the area of direct contact allowing it to rust....Pharmaceutical and food grade items are sometimes passivated as a secondary operation after cutting or machining to eliminate this, but it is costly.....

Thanks,those will work.

Dave Hanks

hsolve
Posts: 67
Joined: Tue Sep 22, 2015 4:23 am

Re: Stainless rusting...

Postby hsolve » Sun Jun 18, 2017 6:50 am

Good morning gents.
hate to be the bearer of bad news, but even 316 S/S will 'rust', develop a 'Tea' stain. If the job is close to the ocean, the salts will over time cause corrosion of the surface. I have pickled 316 S/S parts made for fishing vessels and even they get a tea stain over time. I can be removed with 'Oxailc acid' mixed with water, or it can be removed with electro pickling. Depending on the conditions the slats which dry onto the S/S surface, then absorb humidity from the atmosphere are the worst. It actually forms a brine solution in micro locations on the S/S and if not removed will burrow into the S/S and I mean 316S/S. If you don't want any corrosion or spotting you have to get duplex S/S. Sorry :evil:

johno down under
Posts: 15
Joined: Mon Aug 07, 2017 7:12 am

Re: Stainless rusting...

Postby johno down under » Fri Dec 08, 2017 4:10 am

Hi gents, I have just been reading the above comments about the s/steel.
I am still very new to this whole process, but I have a very good supply of s/steel in two grades 304 and 316.
The guys that I get it off make commercial kitchens and anything under 400mm sq is rubbish and is thrown in the scrap bin!!
Not no more it isn't! at the price of $0 it is all mine. :D ( I just did him a couple of cut outs for his misses)
Now, my question to you knowledgeable fellows is....... is there a difference in cutting these two steels???
One I can cut the 316 and the pieces (free pieces) just drop out and the other one 304 my main cuts are not cutting right at all, they sort of weld themselves back together??
I think (please correct me if I am wrong) the 316 that is sort of polished is the food grade and the other one looks like it has lines (brushed) is the 304 marine grade.
Should there be different settings for the two types ???
Thanks for any advice.
Cheers Johno

User avatar
Gamelord
Elite Contributing Member
Elite Contributing Member
Posts: 1583
Joined: Wed Aug 29, 2012 5:17 pm
Contact:

Re: Stainless rusting...

Postby Gamelord » Fri Dec 08, 2017 11:45 pm

The composition of the two metals are different, 304 and 316. You will have to adjust your cut depending on the one you are cutting.
Once you take flight, your eyes will forever be turned to the sky." "Lack of appreciation is the worlds biggest crime."

Torchmate 6x14 w/THC Downdraft
Thermal Dynamics Cutmaster 101
Corel Draw / Adobe Illustrator
Torchmate CAD


Return to “Tech Tips”

Who is online

Users browsing this forum: No registered users and 1 guest