Tiny rust spots coming through annealed (stained) Stainless Steel?

[Jacob John]

I know the myth about SS not rusting, but I'm having an issues where after washing, a piece I was practicing on is now showing small spots of rust through the annealed (stained) section, ruining the anneal (stain). This was a piece that I slowly stained and there were no visible sparks. Any ideas on how to prevent it? Is it even possible? If this had been a customer item, I would be very unhappy with this result.

[Josh Lucus]

Passivation might help.

https://www.besttechnologyinc.com/passivation-systems/what-is-passivation/

[Jacob John]

Thanks Josh, this looks promising.

[Brian Lamb]

There are also many different varieties of Stainless Steel, the 300 series SS are the most impervious to rust/staining, but a lot of things are made from 400 series, 13-8, 15-5, 17-4 and any number of other grades I can't think of at the moment and they will rust. Passivation is what we had to do on all the aircraft parts, they get dipped in Nitric acid, this would get rid of any surface impurities in the castings and also when machining you would transfer particles of HSS (high speed steel) from drill bits and other tools as you cut the parts

[Jacob John]

There are also many different varieties of Stainless Steel, the 300 series SS are the most impervious to rust/staining, but a lot of things are made from 400 series, 13-8, 15-5, 17-4 and any number of other grades I can't think of at the moment and they will rust. Passivation is what we had to do on all the aircraft parts, they get dipped in Nitric acid, this would get rid of any surface impurities in the castings and also when machining you would transfer particles of HSS (high speed steel) from drill bits and other tools as you cut the parts

The piece that I ran was 18/10 and a few 18/0 pieces though I'm not sure the exact type of SS they were. What's strange is that similar pieces, but different brands, are doing fine with no issues at all. Is there a DIY version of Citrisurf? Looks like a citric acid/water mix.

[Kev Williams]

speaking of transfer- I've had some 304 rust up pretty good, but I'm pretty sure the reason was the SS went thru the same Timesaver that sanded plain steel not long before.

[Jacob John]

I'm kind of wondering if I should test my pieces by running them through my dish washer after to see what rusts and what doesn't. I hate to have to add another step to this process, but I can't have pieces rusting after a few days and the customer washed it. How difficult or time consuming is passivation at home? I think I should stick with citric acid if I try it, but I really wish I could avoid having to use it at all. But these are consumer pieces, not industrial, and I guarantee people will be really angry if their stuff rusts.

[Brian Lamb]

The 18/10 and 18/0 series are used in a lot of silverware, pretty impervious, but eventually you get stains. They used to sell Nitric acid for swimming pools, it's mostly Muriatic now. I used to have a gallon around for stripping cadmium or zinc plating off of hinges before I welded them onto a gate.

[Jacob John]

The 18/10 and 18/0 series are used in a lot of silverware, pretty impervious, but eventually you get stains. They used to sell Nitric acid for swimming pools, it's mostly Muriatic now. I used to have a gallon around for stripping cadmium or zinc plating off of hinges before I welded them onto a gate.


Thanks Brian, I appreciate the responses. When you say eventually, you mean weeks, months, or years? I guess what I'm asking is if I DIY a citric acid mix and treat it, is it worth it? What's crazy is that I'm only scuffing it, so it's not quite annealed (stained), but I'm definitely not engraving so I'm not even sure why it's rusting to begin with. Seems odd that it's revealing enough to make it rust.

[Matthew Herrera]

As mentioned earlier 300 series is probably the most rust resistant. 400 is a very different alloy, I have not worked much with 18/10 or other variations. I suspect you have some contamination from a mild steel used to cut the stainless. You can use a copper sulfate test on the alloy and if any carbon steel is present it will flash a rose copper bluish color. It’s pretty cheap stuff and can be found at most lab or science stores.
The only other thing I can think of is maybe when you heat up the steel with the laser some grain migration is occurring causing the rust protective elements to be void between the grains or vaporized and leaving the steel more susceptible to rust.

[Bill George]

When I was doing stainless projects, I had a stainless steel wire brush and polishing wheels that never touched carbon steel, only stainless. Never any steel wool, it must all be stainless steel.

[Brian Lamb]

Well, it's been my experience that once passivated you might be talking years in time before the parts would take on a stained appearance. We would get airplane parts back for re-work that had seen years of flying through who knows what kind of weather and they would show some slight staining. I think for the cost of some acid it might be worth a try. It's also hard to say how good of stainless you are starting with... given a lot of stuff is made in China, and it's not aircraft stuff where certifications on the material are required... what you really have is anybody's guess.

[Matthew Herrera]

I agree Bill, absolutely anything made of carbon steel coming in contact with the stainless will cause rusting. Including as you said wire brushes or wheels, grinding disk, I wouldn’t even use a polishing wheel. That being said I have a “stainless” Weber grill that I don’t believe on the top surface of the grill has been in contact with any carbon steel, I could be wrong. Anywho it has rust all over the top. It’s easily removed with a wire brush but my point is I believe it’s a low grade of stainless that will rust like carbon steel over a long period of time.

[Jacob John]

So what do engravers that engrave firearms, jewelry, etc do passivation? Outside of industrial applications, who else here is worrying about this after engraving on SS?

[Scott Shepherd]

We've engraved about a zillion things on stainless over the last 10 years. Never seen it, not worried about it. I suspect it was cup/brand specific. What was the brand of cup you used? Any chance it was a China knock off? If so, I wouldn't put too much thought into it and I'd blame it on the cheap cups. If it is a Yeti, I'd not be too worried, since Yeti engraves cups in house as well.

Before I'd start trying to have cups passivated, I'd stop doing cups.

[Kev Williams]

echo what Scott just said, I engrave a ton of stainless (went thru seven 500gm bottles of Cermark last year!) and the only rust issue I can remember was from sanding transfer as I noted above....the same sheet metal shop sanded some aluminum sheets that were black anodized, right after sanding a ton of stainless, lots of silver streaks and small embedded flecks of stainless all because of careless sanding...

I'm thinking it's just a fluke.

As for what may work as a quick fix- get some Naval Jelly (phosphoric acid) and some Magic Erasers. Both are safe to use on stainless, the NJ will take care of any rust, and the ME will help do it quickly! Wear gloves, rinse well and dry...

re: Magic Erasers- while these things will quickly scratch acrylic, and just breathing hard seems to scratch stainless, I use them even on mirror-polished stainless with no scratching or hazing at all. Very aggressive use might, but just basic wiping, wet or dry, they work great. And you CAN get a bit aggressive with brushed stainess, just go with the grain.

[Jacob John]

Interesting Kev and Scott. These are 3 different brands of SS that I stained. Full disclaimer, each was left in the dishwasher after being washed for about a day. They are all supposed to be high quality SS bought from a wholesale distributor, and one is a pretty high end piece that I engraved as a gift. I'm trying to lock down the common denominator but the only thing I can think of is I did use a magic eraser with some Zep to take off the reside left from the staining. Maybe it took off the protective oxide layer as well?

[Scott Shepherd]

All of the cups I have ever seen have a disclaimer on them that says not to put in the dishwasher. If they are the Yeti knockoffs and you are putting them in a dishwasher, then there's your issue. We drop a small piece of paper with "Care guides" on them in every cup we do and it says "hand washing only, do not put in dishwasher". Too much stuff happening in a dishwasher, with hot water. That could very easily cause the issues, in my opinion.

[Gary Hair]

All of the cups I have ever seen have a disclaimer on them that says not to put in the dishwasher. If they are the Yeti knockoffs and you are putting them in a dishwasher, then there's your issue. We drop a small piece of paper with "Care guides" on them in every cup we do and it says "hand washing only, do not put in dishwasher". Too much stuff happening in a dishwasher, with hot water. That could very easily cause the issues, in my opinion.. From what I have been told, the issue with vacuum vessels, YETI, Rtic, etc., is that the heat can break the seal and lose vacuum, rendering the piece useless. If stainless steel was harmed in a dishwasher then virtually every set of silverware known to man would be a rusted mess - the vast majority of it is stainless. It could be the passivation methods, but considering that a huge percentage of silverware is made in China, I doubt it.

[Scott Shepherd]

. From what I have been told, the issue with vacuum vessels, YETI, Rtic, etc., is that the heat can break the seal and lose vacuum, rendering the piece useless. If stainless steel was harmed in a dishwasher then virtually every set of silverware known to man would be a rusted mess - the vast majority of it is stainless. It could be the passivation methods, but considering that a huge percentage of silverware is made in China, I doubt it.

Absolutely it can can break the seal, which is bad. I’m also positive that just washing stainless in a dishwasher doesn’t make them rust. However, when you combine all the elements in this case, I’d bet that the dishwasher helped accelerate this issue.

[Jacob John]

Absolutely it can can break the seal, which is bad. I’m also positive that just washing stainless in a dishwasher doesn’t make them rust. However, when you combine all the elements in this case, I’d bet that the dishwasher helped accelerate this issue.

And maybe that's it. I'm thoroughly confused. It was several different brands, two of which are at least labeled 300 series SS. It should have a high enough nickel content to not rust, so either these brands lied about the high nickel content (which I don't believe), the dishwasher accelerated the rust (which definitely is sound reasoning), or there's something common among them that happened to cause it.

As a test, I have two pieces that I've left in water for the last several days, and neither have started to rust. All I did for cleaning these was use blue Dawn and water, NO scrubbing from a magic eraser, and NO Zep. So far, no rust.

Oh and just for clarity, the rust is on the exact spots where the SS was stained. The rest of the rusted pieces are fine, and I'm sure in scrubbing them, those sections got both scrubbed and Zepped.

[Scott Shepherd]

It’s not hard to make stainless rust. In my machinist years, I’ve seen it many times. Want to see it rust? Sand a piece and set it on a piece of wet wood and leave it.

Having said that, I’ve never seen it in the engraving world on cups. Keep in mind, 18-8 is most likely 304.

[Matthew Herrera]

I’ve engraved quite a few stainless Hydroflask and never had a rust issue. I can’t tell you what grade stainless they were but never saw one spot of rust. I’m really thinking the dishwasher had a part in this. High temps, and PH can increase corrosion rates in stainless. But then again our “silver ware” should all be rusting too.... is it possible this is some kind of galvanic corrosion? Different alloys in an electrolyte will cause galvanic corrosion when one metal becomes an anode and the other a cathode.

[Kev Williams]

just curious, what brand of detergent you using in that dishwasher?

[Jacob John]

just curious, what brand of detergent you using in that dishwasher?

It's those Cascasde Platinum tablets.

[Scott Marquez]

I sell welding supplies at my day job and I sell a product called Bohler "Blue one" used to pasivate welds on Stainless steel, which is a pretty tame product, I also sell "Red one" which is much stronger.
Scott

[Jacob John]

Just an update to this thread, but I went crazy and frosted a bunch of my personal flatware (18/0, and some 18/8) and then stained (annealed) a few bread knives and other kitchen utensils. I ran them through several dishwasher loads and guess what? The flatware is not rusting, but the stained knives are rusting like crazy. Now, the pieces I've stained range from some high dollar, high quality SS knives (my wife isn't happy about this :D) to some garbage you buy at the dollar store. Made no difference. Is it the detergent, heat etc? Could I convince a few of you to try the same thing and let me know what it does? I can't stand not knowing what's causing this! :eek:

Maybe it's the quality of Houston water? Haha

[Brian Lamb]

Stainless steel knives are most likely some form of heat treatable stainless, and it will all eventually rust. You can't hold an edge on rust proof stainless.

[Jacob John]

Stainless steel knives are most likely some form of heat treatable stainless, and it will all eventually rust. You can't hold an edge on rust proof stainless.

So maybe there's the answer. The flatware isn't rusting, but all the knives are rusting. So if that is the answer, beyond hand washing and immediately drying, is there any treatment that would slow or impede rust?

[Brian Lamb]

Hard to say not knowing the exact material, but I would suspect the passivation process would help remove any "rustable" material from the surface that might have been raised, disturbed or uncovered by the laser process. At this point, you are pretty much at a try and see type situation. Oh the joys of doing one-off work on unknown materials.... you never know what might happen.

[Jacob John]

Hard to say not knowing the exact material, but I would suspect the passivation process would help remove any "rustable" material from the surface that might have been raised, disturbed or uncovered by the laser process. At this point, you are pretty much at a try and see type situation. Oh the joys of doing one-off work on unknown materials.... you never know what might happen.


You know, I sound like a broken record when I post this in fiber laser threads, but we are guinea pigs in every sense of the word. :D Even the manufacturers of these things don't or won't share even baseline settings for materials. I find that to be telling in so many ways. I've basically begged for settings and can't get them!

[Kev Williams]

OK, so take some of what you frosted that's not rusting, and do some annealing on the same piece and see what happens...

A description (that I read somewhere) of what's actually happening during 'annealing' (via fiber laser), is the carbon at the surface of the metal is being oxidized... if the metal is SS, this would likely compromise the rust-proofing ability of the chromium at the surface, leaving the now oxidized carbon vulnerable to rusting.

Hey, sounds good to me! :D So anneal 2 pieces of frosted silverware- then wash one in the dishwasher, and leave the other one in a pan of dish-soapy water-- I'll bet a buck the dishwasher will rust the annealing while not rusting the frosted (which still has it's chromium intact) and it'll take a year or more for the piece sitting in regular dish soap and water to rust...

Dishwasher soap will oxidize and etch aluminum oxide (aka anodizing), I'm sure it'll have no problem rusting rustable stuff! ;)

Easy solution: don't put in the dishwasher! :)

[Scott Shepherd]

Even the manufacturers of these things don't or won't share even baseline settings for materials. I find that to be telling in so many ways. I've basically begged for settings and can't get them!

Sure they will. SPI has a lot of settings for various materials. However, you have to go high end to get their systems. What so many of us are dealing with is a lower cost unit at the expensive of support and features. Want quick answers and guidance on settings? Spend $40K on a laser. Want to take the time to have to figure everything our yourself, fix you own machine, and be limited in functionality? Then don't buy a $40K laser. How much time/money is lost chasing these issues? Answer? A lot. At $90 per hour, figuring this issue out has cost over $1000 in lost revenue already, I'm guessing (it would if it were done in my shop).

We are lucky that SMC exists because without the crowd sourcing of tech support on this forum, many of these machines would be boat anchors (not suggesting anyone in particular, just a general comment).

I wonder what the $40K laser would cost if they stopped all their support and just let the users figure it out themselves.

[Gary Hair]

I wonder what the $40K laser would cost if they stopped all their support and just let the users figure it out themselves.

About the same as the typical Chinese machine.

[Scott Shepherd]

About the same as the typical Chinese machine.

Probably a little better since you have much higher quality laser sources and parts instead of things that were reverse engineered around those items. Many of the remarkable things we see demonstrated on fibers are up above the 150KHz range, and most Chinese sources are capping out at 80KHz.

The old saying "You get what you pay for" rings very true on fiber lasers. Want access to top notch support? Spend $40K. Want to figure it out yourself? Spend $6,000, then the next 3 years dialing it in :) (yes, I'm exaggerating)

[Jacob John]

Scott, look at my sig. :) For fibers, setting recommendations are nearly non-existent, even from the big boys. My source is SPI and is a Tykma. Tykma only has an outdated pdf for some settings that isn't up to date with their software. That manual is almost 10 years old.

For CO2 lasers, your point is valid though maybe Trotec and Epilog are different and offer a ton of recommended settings for their fibers.

[Scott Shepherd]

Scott, look at my sig. :) For fibers, setting recommendations are nearly non-existent, even from the big boys. My source is SPI and is a Tykma. Tykma only has an outdated pdf for some settings that isn't up to date with their software. That manual is almost 10 years old.

For CO2 lasers, your point is valid though maybe Trotec and Epilog are different and offer a ton of recommended settings for their fibers.

I'm aware of your source. However, SPI has a vast technical library that has a ton of information there. If your supplier isn't up to speed on that stuff, then they probably aren't a good supplier (at least as far as the way I rate suppliers).

EZCAD is, as far as I understand, a pirated knock off of a western software program. They clearly didn't write the code. If they did, then they'd show that they have people fluent in English behind the scenes. If they did, you wouldn't see things like "rorate" instead of "rotate" and examples like that, that never get fixed. Someone in the western world wrote the original program, and my guess is that the people who wrote it, and offer it to manufacturers to do with their sources, know their stuff inside and out.

Fiber lasers have been around a long time. This isn't a new thing. There are many, many companies that have been doing it for a long time and really know their products. I have yet to see one them mentioned on this forum because the majority of people are looking to get a fiber laser for $6500.

Like I said, you get what you pay for. And I'm not saying anything negatively about it, just stating my opinion, as someone who's owned a fiber laser for about 3 years now and have been dealing with the EZCAD and the likes since then.

I got a call from a friend asking me if I could come look at their lasers. Two galvo fibers. I went and they were super high dollar machines. $90,000 each. I went through all the software and saw how it was working and how the flow worked, and without question, that software was superior to EZCAD. So options are out there, just not in the $10000 or less range.

[Jacob John]

Sorry I didn't see this post, Scott. My fiber is an American made system with an SPI source so I don't know if SPI specifically would share that info, though it would great if they did. Tykma does offer a manual that anyone can download with recommeded settings for a good bit of materials, but it needs to be updated. They have really good customer support, but they don't freely offer settings. You can request their help and they will help, but what I want is their comprehensive settings! :D

The CAD that they offer is not a Chinese knockoff, it's their version. I guess I'm not explaining it correctly, but I'm guessing its source code is CAD with their programming on top of it. No misspelled words or anything like that at all. It's a very user friendly piece of software. And my fiber isn't one of the cheapies, it's a US made machine with US support. I do know what you mean though.

As to the topic, I engraved another piece of SS last night and I used ZEP to scrub it, washed it with water, left it out without drying it (intentionally) and sure enough it's got rust spots. It has to be that a combo of a cleaner/degreaser along with a magic eraser cause something in the metal to be revealed and start rusting. I'm pretty safe in saying that now after marking some pieces and not cleaning other than water (no rust).

EDIT: Oh and I forgot to add the real key piece of evidence to support my theory. Areas that were not lasered have small rust spots. That means part of the cleaning process is removing the protective layer from the SS.

[Kev Williams]

I engraved another piece of SS last night and I used ZEP to scrub it...There's a lot of ZEP's on HD's shelves, but IF you're talking the purple stuff, which is a Castrol SuperClean knockoff, IT's likely the reason for the rust, one of it's main cleaning/degreasing agents is sodium hydroxide, aka Lye...

[Dominic Notaro]

Best check for stainless steel is with a magnetic. High grade stainless won't attract a magnetic and won't rust. If it attracts a magnetic it will rust have to put on a protective coating to provent it from rusting.

[Scott Shepherd]

Best check for stainless steel is with a magnetic. High grade stainless won't attract a magnetic and won't rust. If it attracts a magnetic it will rust have to put on a protective coating to provent it from rusting.


I'd disagree with just about all of that. There is no such thing as "high grade stainless". Certainly the 400 series (magnetic) is considered anything but low grade and used to make a lot of very high end products. You can make most all stainless steels rust. They are prone to rust when oxygen is taking away from them. When freshly scratched, stainless is open to rusting until it "heals" itself with the protective skin it has on it.

Stainless isn't rust free, it's rust resistant. Two totally different things.

[Jacob John]

Since the thread was bumped, the SS I engraved and have left in my dishwasher for a week now shows no signs of rust at all (not ZEP cleaned).

The ZEP 505 cleaned pieces are rusting like crazy. So I think it's definitely the ZEP though here's a curious question. Why is it recommended for those powder coated tumblers after engraving? I don't have any issues with those.