Rust in Stainless Steel Sink?

Has anyone ever had issues with rust appear in stainless steel sinks as a result of photo chemistry? I recently began processing b/w at home, and the utility sink I am using is developing strange rust spots. I don't know if these are due to chemistry or something else. Using XTOL, Ilfostop, Ilford Rapid Fixer, and Photo-Flo.

Stainless steel does indeed rust if you treat it harshly enough. It's still mostly iron! I also use a cheap stainless steel sink in my darkroom and I can confirm that it has some iffy spots by now. Photochemistry is pretty hard on stainless steel, especially if you don't clean it up immediately and thoroughly.

It will depend on the grade. Photo grade can take continuous contact with photo chemicals for decades without change. We used the same set of SS trays the entire 45 years I was associated with the university darkroom...and they were in use a decade or so before I got there...darkroom was only closed from midnight to 8am, 7 days a week (and sometimes never closed). Never a hint of rust. Occasionally chemicals (Dev, Stop, Fix) would evaporated dry in them if someone blew it before a long break.

With current crop of SS material, meaning last 10+ years at least, is no longer of quality. While there are different grades at related costs, for specific purposes where it really counts (like surgical tools or food processing industry), most of the rest is not as good as it used to be. However, rust spots are not unusual in consumer grade SS and often can be cleaned up with products like Metal Brite.

As already said there are various alloys of SS, which also vary in chemical resistance. Furthermore thermal load on SS during working on (as welding) may harm the resistant character of its surface, so that the surface has to be chemically treated afterwards at these locations to regain its characteristic.

The most aggresive bath concernig SS was in the Cibachrome/Ilfochrome process.


Also there is the chance of iron being mechanically deposited on a SS surface, what also may lead to a rusty surface.

I often have a little rust residue in stainless steel sink, but this is only when I am negligent changing filter for well water. Rust wipes right off. As noted above, there are grades of stainless steel. In order to cut manufacturing costs, use lower quality steel from China.

"Lower quality" steel is or was produced overall the world. As I tried to indicate above, but likely I did not make it clear, steel has various properties. The most important are mechanical and chemical. Reducing one of these two may mean making it even super quality in that respect.
As cost is factor, or tooling too. that alloy is used that is sufficient for the respective use. In our case that could mean an alloy good enough for nearly all darkroom work is not sufficient long time with Cibachrome for instance.

Yes, both developer which is very basic and stop which is acidic will attack sinks. I replaced a sink strainer once and sadly left my Nova tank to drip into the sink through the drainage tubing; Maybe a drip every 30 seconds. The new sink strainer assembly lasted one week before it rusted through completely and separated from the sink under neath the cupboard.
Flush with plain water after usage!

Many years ago, I used to get strange rust spots and little circular discoloration spots in the Arkay stainless steel sink. I always suspected the water--maybe had some iron content--but I had it tested several times over the years and it was fine. The remedy was not pleasant! I don't remember what exactly I used, but it was a VERY strong acid that required careful technique to keep yourself safe. Never had any issue with my Arkay stainless steel trays, though.

Thanks for the replies. Yes--the rust does clean off pretty easily, I'm just trying to identify the source (and am hoping that it's not the photo chems). I do a pretty good job cleaning up the sink during and after use. I suspect the quality of the SS is inferior, and that the source of the rust is something else (e.g. residual metals from cleaning cast-iron stove grates). We live in the city, so seems unlikely that there is iron/rust in the water.

AgX said:

"Lower quality" steel is or was produced overall the world. As I tried to indicate above, but likely I did not make it clear, steel has various properties. The most important are mechanical and chemical. Reducing one of these two may mean making it even super quality in that respect.
As cost is factor, or tooling too. that alloy is used that is sufficient for the respective use. In our case that could mean an alloy good enough for nearly all darkroom work is not sufficient long time with Cibachrome for instance.

Click to expand...

All true, except that for lower designed quality SS there is still manufacturing and quality control that can be "adjusted" so criteria of a particular alloy are met, yet not exactly. China used be known for selling inferior end product, including steel, of any kind. While this is not as clear these days it still exists. In shipbuilding for example, what is now a rather common to use a Chinese steel at any yard worldwide, the steel quality has always been not up to the expected par, although this is less of an issue today vs. say 10 + years ago.

But alloy's chemical content is one thing, and how they are manufactured another, so you can have a technically same steel content wise, yet it does not perform as expected. This is especially true with higher grade products where for example annealing is critical to get final plate up to specs, and that's when things typically would go wrong (call it shortcuts in production).

Same applies to SS where it is not just about content ratios of different components (and quality of each), but the impurities that make the difference. So one buys a specific grade of SS, then sees things happen that should never have, like pinholes developing shortly after being put into use. And yes China is historically guilty of introducing products to the global markets nobody thought before was a marketable product. Sadly, China has found followers just about everywhere, so inferior product is no longer in their fixed domain. Meanwhile, China has addressed a lot of issues, and given right QC and specific end customer, they are now capable of high grade production, if they so choose. Automation and digital production control has helped a lot too.

johnrousseau said:

Thanks for the replies. Yes--the rust does clean off pretty easily, I'm just trying to identify the source (and am hoping that it's not the photo chems). I do a pretty good job cleaning up the sink during and after use. I suspect the quality of the SS is inferior, and that the source of the rust is something else (e.g. residual metals from cleaning cast-iron stove grates). We live in the city, so seems unlikely that there is iron/rust in the water.

Click to expand...

Since it cleans off easily, it may likely not be the stainless the sink is made from, but rather discoloration from whatever is being put into it, a different matter altogether.

Many stainless steels will later rust if cleaned with "steel wool".

If you use steel wool, be sure to use stainless steel wool.

If you use ordinary steel wool small bits of the wool will get trapped in the grains of the stainless steel of the sink …. and then those bits of ordinary steel will rust.

There are several different types of stainless steel, but they CAN rust. It depends on their alloy composition. They all contain a small amount of iron, which can oxidize and form rust. The best darkroom products are made of Type 316L stainless, which is ductile enough for forming into shape without cracking, and has a reduced carbon content (“L” stands for low carbon) for products that require welding, such as the corners of a sink. But it’s important that the welding rod that’s used in welding the corners also has a low carbon content in order to maintain the corrosion (rust) resistance; this bypasses the need for annealing the finished product. My Leedal ss sinks were bought new 17 yrs ago and with proper care per their instructions still glisten and are rust-free. After a few printing sessions I clean/polish with a product called “Stainless Steel Magic” which leaves a protective film that, repels water and other stuff. For duckboards, I’ve always used corrugated fiberglass roofing material bought at Home Depot that are easily cut to length to fit the sinks - and they’re inexpensive. At the end of a session, I spray them and the sinks with water, then dry the sinks and stand the duckboards on end in the sinks with towels underneath them to air dry.

Incidentally, if a magnet sticks to the stainless, it’s not 316L.

I’ve attached the pdfs from Leedal for cleaning/care of the sinks. Good reading.

Steve Goldstein said:

Many stainless steels will later rust if cleaned with "steel wool".

Click to expand...

All stainless steels will corrode when cleaned with steel wool. The beauty of stainless steel is best maintained with a feldspar cleanser. Eastman Kodak always recommended Bon Ami brand of powdered cleanser. Never use Comet or any cleaner with chlorine.
Nikor and other (Arkay etc.) are 316 stainless steel. 300 series stainless is high in nickel, which helps when drawing the steel (like making a Nikor tank.)

400 series stainless is more common today, a magnet will stick. 400 series works fine for certain applications, very low in nickel, hard, used in cutlery.

A term 18-8 is used to refer to 18% Cr, 8% Ni. SS needs to maintain a protective layer of Chromium Oxide. To refresh and deep clean stainless, traditionally a final rinse with nitric acid was used to "passivate" stainless steel by restoring the Chrome Oxide. Citric acid is used more and more today for passivation.

You can pit a stainless sink by leaving a plastic container that traps water, and most importantly some iron particles, on the sink.

It's simple galvanic corrosion. Look up a table in a materials handbook ,galvanic series of metals.

Bottom line no steel wool, no chlorine, occasionally passivate with nitric or citric acid (never muriatic or HCL) , Zud or Bon Ami no additives old fashioned cleanser, and green Scotch Brite.

We used the green scrubbing sponges (Scotch Brite?) and elbow grease. The sink got that, plus the Comet cleanser (not SS).

freecitizen said:

If you use steel wool, be sure to use stainless steel wool.

If you use ordinary steel wool small bits of the wool will get trapped in the grains of the stainless steel of the sink …. and then those bits of ordinary steel will rust.

Click to expand...

Never use the steel Brillo pads to clean your SS sink (or trays),