Stainless Steel A304....discoloration problem

Date 10-15-2010 13:16

Hi,
A power wire brush should remove the discolouration but you would probably need to brush the entire area to achieve a uniform finish. I would prefer to use a pickling paste which should re-passivate the areas and will also remove all discolouration. However, be aware that pickling pastes are nasty when not used correctly so you may need to consult with your health and safety dept before hand.

46.00

By jwright650 (*****)

Date 10-15-2010 15:58

Thanks for the reply, not sure how well they can apply the passi-paste overhead and not get that stuff all over themselves.....SS is not our forte', it got added to our contract and I'm not sure how to really deal with this stuff. The A304 that was used has a brushed look to it and it really isn't very pretty from an architectual standpoint, but that is what they spec'd. I'm hoping we can get the erector to brush these spots for us and not have to brush the whole entire surface....there is alot of surface area, as these plates go around the perimeter of the building.

By MMyers

Date 10-15-2010 17:32

If you have alot more of these to do, you might want to consider back purging the plate. It'll be a PITA, but it'll eliminate the secondary operation. We use small trailing shields (SS box with mesh over one side) and argon for this.

By jwright650 (*****)

Date 10-15-2010 17:44

Thanks for the tip Mike.
I'll have to save that trick for the future....all of this project is currently in the field and erected. I'll have to make sure our Estimating Dept understands the extra work required that is required so they can add enough shop hours to cover it. When the field report came in with the pic attached, I told my boss that we needed to shield the back side to keep that from happening, but wasn't sure how to accomplish that. Plus this stuff gets welded in the field too after they erect it and get the adjustments made for the brick masons.

By aevald

Date 10-15-2010 18:26

Hello John, I realize that I'm really late in adding to your post. As 46.00 pointed out, there are many passivation choices that could be considered for the issue that you have in those photos. I am curious, have you tried the search function on the forum here? I recall a number of threads that discussed the many ways to "clean" various stainless steel items, both large and small. Once upon a large number of years ago I was doing some work at a fabrication complex that dealt with a lot of stainless steel items, much of it was food grade type stuff so it had to look really nice, etc. They used a system that employed a "stick" with a sponge on the end of it which was also hooked up to some form of an electrical doo-hickey which also had a ground clip that would be attached to the work. They would dip the sponge into a chemical and then brush it over the discolored area, it would basically erase the discoloration and return the stainless to a dull silver color which could then be finished additionally to whatever sort of finish was required. I believe Chuck Meadows also posted a large amount of information which might address your issue. Best of luck and regards, Allan

By eekpod

Date 10-15-2010 20:55

I'm sure Home Depot sells silver paint :)

By jwright650 (*****)

Date 10-18-2010 15:32

Hi Allan,
I've been reading through the forum on the various SS threads and I have to say that I'm more confused now that when I first started....geez, why in the world does anyone want to specify using a material with so many problems and precautions associated with it?...LOL

By aevald

Date 10-18-2010 19:48

Hi John, I very quickly took a look at these two sites: www.avestawelding.com and www.avestafinishing.com , you may wish to peruse these a bit with your newfound involvement in the stainless world, I believe there is a lot of really good info. relative to stainless steels and other good stuff.
I understand your questions and concerns if you haven't been involved with stainless steel materials much in the past, there is plenty to learn and likely never master. Best regards, Allan

By ssbn727 (*****)

Date 10-18-2010 21:57

ROTFLMFAOAAA!!! :) :) :)

Hey John, use the 'Scotch-brite" pads and you should be fine... The only concern the client has is having the Chromium oxide layer on the surface (Blue-ish discoloration) being exposed for a prolonged period around the "elements/atmosphere" where this structure will be... So, in order to prevent any accelerated corrosion there, that layer needs to be removed to the degree where only a shiny metal surface is present and as a result, this will start to automatically passivate (forming a protective layer which will protect the Stainless steel underneath the surface from corrosion and further oxidation.) itself almost instantaneously without the aid of chemicals since it is a chemical reaction in itself. ;)

Now you may need a "chemical helper" (pickling/passivating agents) if the chromium oxide layer is thicker than usual and cannot be totally removed with the scotch-brite pads alone... Most reputable welding supply houses/distributors usually carry something that's relatively inexpensive should you need the "extra help. ;)"
Btw, did this client list any special instructions regarding this specific situation in the general notes??? Anywho, hope this helps. ;)

Respectfully,
Henry

By jwright650 (*****)

Date 10-19-2010 12:43

I'm going to try some citric acid cleaner on my samples and see how that goes. I found a couple pieces of this A304 at a fitter's table where they sawed off of something that came in too long, ran a bead of SMAW weld on the plate(s) and watched the brownish color appear on the backside...so now I have two samples to play with.

By jwright650 (*****)

Date 10-20-2010 15:52 Edited 10-20-2010 16:00

UPDATE:

Our project manager went to a meeting yesterday to discuss this issue and to see what sort of linear footage we were looking at.
Lots of linear footage...5 floors worth

A trip to the grocery store proved to be beneficial. 100% Lemon juice is cheap and worked fantastic, and CLR worked even better but a little more expensive.

as a side note, this is neat-o: http://70.38.98.68/PortalBuilder/WebPages/WebPage.aspx?wId=1523

video: http://link.brightcove.com/services/player/bcpid3344859001?bclid=3350299001&bctid=3562415001

By aevald

Date 10-20-2010 17:59

Hey John, looks as if you may have hit the jackpot for your challenge there. As you said lemon juice is pretty cheap and certainly environmentally friendly. As to CLR, I can't say anything about it's environmental issues. Looks good. Best regards, Allan

By ssbn727 (*****)

Date 10-20-2010 20:31

Good work John!

The Citric acid is just the trick especially if you want to maintain that sort of finish. ;) Btw,what is this structure for?

Respectfully,
Henry

By rodofgod (**)

Date 10-20-2010 20:55

John, you seemed to have found quite a bit of info about stainless that many on here didn't know about! The citric acid is one I will remember for the future!

Regards

By ssbn727 (*****)

Date 10-20-2010 21:30

I respectfully disagree with that statement since after all, it was me and others who posted some specific information regarding Citric acid in some previous posts which John was able to review some of it from quite some time ago Glen. ;) I'm just glad the was able to use it on this project. I will say that the use of CLR is news to me, and I would be just a bit cautious before using that stuff since it may have some ingredients that may not be beneficial to the passive layer long term when compared to citric acid and it's certainly not as environmentally friendly as the lemon juice is. ;) Here's the link I'm referring to:

http://www.aws.org/cgi-bin/mwf/topic_show.pl?pid=181641;hl=

Respectfully,
Henry

By jwright650 (*****)

Date 10-21-2010 10:51

Yup, that was the thread that made me put on my thinking cap.....I was unsure which citric acid would work the best(orange or lemon), but I picked up the lemon because it said 100% lemon juice on the jug, and figured it had to be stronger than the watered down orange juice.

By rodofgod (**)

Date 10-21-2010 23:08

Hi ssbn727!

I stand corrected!

Regards!

By OBEWAN

Date 10-20-2010 23:10

I should have thought to mention the citric acid option. A few years back I was reading about passivation from Googled websites and heard about lemon juice being used. I did not think it very aggressive, but I suppose together with a scotchbrite or maybe without it is.

By jwright650 (*****)

Date 10-21-2010 10:46

Henry,
These are lintels that carry the brick over windows in a building. Normally the owners paint these a brick color and they disappear, but for some reason they added these SS plates to our contract and in the rush of trying to get these done, we didn't notice or pay any attention to the fact that the bottom of these would be visible after construction(like I stated earlier, they usually get painted and I don't have to think about if the heat showed through after welding).

By ssbn727 (*****)

Date 10-21-2010 17:58

Interesting to say the least John... Thanks for your reply. ;)

Respectfully,
Henry

By Eutectic (**)

Date 10-21-2010 09:29

John,

Just a cautionary note on the handling of stainless for aesthetic applications. bear in mind that the susceptibility to corrosion and discoloration will increase with the material surface roughness. i have a article somewhere but i am sure you’ll find something on Google. so when you buff the material or prepare weld edges make sure the guys don’t grind unnecessarily on the base material adjacent to the weld.

Cheers

Attachment: NewPicture.bmp - Salt spray test corrosion vs surface roughness (353k)

By DaveBoyer (*****)

Date 10-22-2010 00:14

You bring up a good point. The hot rolled finish on SS doesn't always stay nice in service. Carbon transfer from handling and oxygen starvation from instalation are 2 frequent problems.

By jwright650 (*****)

Date 12-07-2010 11:48

New update:
Regardless of our attempt to bring the A304 back to it's natural color and finish(which is better than we received it from the mill), we have ran into an Architech who has refused our efforts completely and wants this to look like a polished appliance. Check out the pic of the sample he showed my guys yesterday of what he is now asking us to mimick.....wow, I hope our people can get an extra to the contract for all of this extra work.

By jwright650 (*****)

Date 12-07-2010 11:57

Oh and to add to this problem check out this pic of where the brick guys cleaned their brick and tarnished the bottom of these lintels even further.....uggh. Our guys started to clean this and it started turning even darker....I'm guessing that muratic acid was used to clean the brick and is reacting with our solution.

By ronnie taylor (**)

Date 12-07-2010 14:07

Mr. Wright

Have you thought about brasso?

Ronnie

By jwright650 (*****)

Date 12-07-2010 14:56

Whatever the brick guys used is turning the SS dark when we try to clean it with anything, and I'm afraid that brasso will get down in the grainy mill surface and make it look chaulky. I probably won't be able to get anything like a polish out of the brushed looking finish without sanding the mill surface down smooth and gradually working to finer grits until it gets shiny enough to satisfy this guy.

I can't see this as a winnable situation for either us or the Architech at this point, we are both unhappy with this situation.

By weldwade (***)

Date 12-07-2010 22:01

John,
I had a similar issue with 6 condos in Telluride Colorado. These were very expensive units with a similar reveal to the stone work but it was a painted mild steel beam that was rusting at places. The solution I ended up with was a .060 polished SS trim bent to fit the application and fastened on the inside of the trim for aesthetics. I used SS weld on 1/4-20 studs to the painted beams, rented the stud machine from a rental company. The builder then had a painting contractor fix the paint issues. The pieces of trim were 4' long by about 10". Then I marked the location for each hole in the trim, drilled the holes and modified my air ratchet to tighten the bolts, so I had to fit each piece as I went then fasten as I progressed. I taped a push broom handle to my air ratchet with the button depressed and installed a ball valve in my air line for my helper to operate the ratchet. It worked out slick and the builder was very happy with the look. The corners got a fabricated "corner cap" that I pop riveted on. The builder started calling me MacGyver... Duct tape and a broom stick fixed him up!

By TimGary (****)

Date 12-07-2010 13:30

Wow... that architect must be on drugs, or is completely clueless, both of which are likely...
IMHO, the better, cheaper, faster way would be to screw fasten a sheet metal trim covering, after most construction is complete.

Tim

By jwright650 (*****)

Date 12-07-2010 14:59

Tim,
I thought about adding a thin(.060") SS polished strip to the bottomside, but was unsure how to fasten it. I would need it to be in several widths from 6" up to 30.5" and in lengths up to 30 feet or more.

By TimGary (****)

Date 12-07-2010 20:31

John,
Looking at your picture showing discoloration, it looks like there's a drip edge 1 brick up from the bottom.
A trim piece could be fastened underneath to the drip edge with SS pop rivets.
I'm not sure where to fasten to under the bottom, but where there's a will, there's a way...
Any metal building manufacturer, like MBCI, could fold trim in any shape out of any typical material you want.
I don't recommend having trim made in lengths over 12', because the shippers and/or installers will probly bend it before it could be fastened.
Trim is normally made 2" long (i.e. 12' 2"), in order to account for overlap on the ends, where the seams are screwed or riveted together.

Tim

By DaveBoyer (*****)

Date 12-08-2010 03:26

That arcitect had NO IDEA what a hot rolled finish on stainless looks like. The sample You posted looks like an abrasive brushed finish done to cold finished stock. You can by stock finished like that for the trim pieces You mentioned. Cold finished stainless only comes up to 7 gage thickness, so the architect was way off the mark in his expectations.