Metallurgical Question About Stainless Steel Corrosion

[A. Jacobs]

I was researching stainless steel grades on wikipedia and I ended up reading about the different kinds of corrosion associated with stainless.

This may sound like an absurd question, but it is a legitimate one. I figured I would post this and see if there are any steel experts on this forum because I myself am certainly not.

My question is this:
Is an austentic stainless steel, such as 904L, prone to rouging under normal freshwater conditions? I have read on several websites that rouging occurs in an ULTRA PURE WATER environment.The passive layer on the surface of stainless steels can breakdown by the interaction of ultra pure water, which is devoid of ionic species, leading to rouging, or rust blooms. The ionic pull of the water is strong enough to strip the protective chromium oxide off the steel surface. This results in the stainless steel having to re-passivate by reforming another layer of chromium oxide film, which incorporates the rouge causing discoloration. During the brief time it takes to repassivate, a thin layer of the stainless steel dissolves, or corrodes.

Another question I have is: What exactly is ultra pure water that lacks ions?
This is a concern of mine because I clean my watches by submerging them in a container of bottled spring water for about an hour every couple of weeks.
I do this because I don't like using hard tap water.

Does the passive layer of the stainless steel get pulled off of the surface of my watches when they are submerged in purified spring water for an hour or so? Or am I completely confused about what ion free ultra pure water is?
What I have read suggests that stainless is more likely to suffer from this form of corrosion in "ultra pure water" than in seawater with high chloride content.

Lastly is this: Can stainless steel re-passivate while submerged in water, whether it be seawater or "ultra pure" water?
Any help on this matter is greatly appreciated

[Incurable]

Based on what you're saying, I'd stay away from de-ionized water. I am by no way a metallurgist but... for my car, only distilled or de-ionized water is appropriate for my cooling system. Other waters will react w/the aluminum and cause corrosion/electrolysis problems. You can buy either distilled or de-ionized water at the market in gallon jugs. Are 'ultra pure' and 'de-ionized' the same? Sound close if not close enough...

[A. Jacobs]

Originally Posted by Incurable

Based on what you're saying, I'd stay away from de-ionized water. I am by no way a metallurgist but... for my car, only distilled or de-ionized water is appropriate for my cooling system. Other waters will react w/the aluminum and cause corrosion/electrolysis problems. You can buy either distilled or de-ionized water at the market in gallon jugs. Is 'ultra pure' and 'de-ionized' the same? Sound close if not close enough...

Pat,
I'm not sure what ultra pure water is. I was hoping someone here would be able to shed some light on this subject.
When you really think about this question I have posted, you start to realize how absurd it sounds as far as getting an underwater watch wet in the wrong kind of water.

[Kris]

Originally Posted by Incurable

Based on what you're saying, I'd stay away from de-ionized water. I am by no way a metallurgist but... for my car, only distilled or de-ionized water is appropriate for my cooling system. Other waters will react w/the aluminum and cause corrosion/electrolysis problems. You can buy either distilled or de-ionized water at the market in gallon jugs. Is 'ultra pure' and 'de-ionized' the same? Sound close if not close enough...

Besides promoting corrosion, hard-water calcify's and starts to "scale" when heated and cooled at extreme temperatures. Chances are your radiator would get plugged up with all the calcium build-up in between the fins and water paths first before any corrosion would start.

An aluminium radiator will tend not to corrode or won't corrode at all, but would still have scaling build-up, hence, it's still advised to use soft-water in your cooling system even if the rad is alum.

Sorry, I still can't answer the question about the reaction with 904L steel though

[Incurable]

From what I've been able to garnish (google), ultra pure water is water purified to the utmost possible level, including de-ionization (both conductive and non-conductive) for scientific purposes. I highly doubt this would be a 'real world' concern when it comes to exposing your Rolex to water. Spring water may be purified to some extend but I don't think it even comes close to meeting the standards of 'ultra pure water'. I'll leave the specifics to those who know a whole bunch more than I.

BTW, by corrosion, I guess I really meant galvanic corrosion.

[A. Jacobs]

Originally Posted by Incurable

From what I've been able to garnish (google), ultra pure water is water purified to the utmost possible level, including de-ionization (both conductive and non-conductive) for scientific purposes. I highly doubt this would be a 'real world' concern when it comes to exposing your Rolex to water. Spring water may be purified to some extend but I don't think it even comes close to meeting the standards of 'ultra pure water'. I'll leave the specifics to those who know a whole bunch more than I.

BTW, by corrosion, I guess I really meant galvanic corrosion.

Pat,
Thanks for the input. I too have been researching this topic on google since yesterday afternoon.

[Lol-x]

I have just spoken to a metallurgist with a PH.D. in physics.

From my brief discussion "ultra pure water" is something much purer than rain or spring water. It is water that has had significant amounts of salts and gases removed. It appears to be a type of water that may only be found if it is produced in a laboratory.

Ultra pure water is so pure that it contains less than 1 microsieman per centimeter at 25 degrees, where microsieman is a measure of conductivity.
If you had 904L stainless and it was heated to say 60 degrees you may see some staining over a period of weeks, however at room temperature there would probably be no visible effect.

So your watches will be fine in distilled or spring water.

[nko51]

904L stainless does not rust, it's the iron in the water that turns to rust.
60 year old cars in junk yards have a heavy build up of surface rust, why because once upon a time in America they blended 5% nickel into the steel, now who knows.

[GerardoG]

I wash my watched with distilled water before storing them back @ safe, no problems so far.