Salt and stainless steel

[paulraphael]

I've read that you need to be careful with even high grade stainless steels and salt ... like don't salt the water until it's already simmering, so the salt goes right into solution rather than sitting on the bottom of the pan.

Any thoughts on this?

I roast mostly with clad metal pans, both with 18-10 stainless interiors. I don't want to pit them, and I'm wondering if salting the food in them before putting them into a 500 degree oven is an invitation to pitting.

I've noticed a small pit on the stainless interior of my favorite copper saucepan. No idea how it got there, but if possible I'd like to avoid getting any more.

[ray goud]

I've read that you need to be careful with even high grade stainless steels and salt ... like don't salt the water until it's already simmering, so the salt goes right into solution rather than sitting on the bottom of the pan.

Any thoughts on this?

I roast mostly with clad metal pans, both with 18-10 stainless interiors. I don't want to pit them, and I'm wondering if salting the food in them before putting them into a 500 degree oven is an invitation to pitting.

I've noticed a small pit on the stainless interior of my favorite copper saucepan. No idea how it got there, but if possible I'd like to avoid getting any more.

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Yes, it's a good idea not to allow salt crystals to sit, undissolved, in SS. If they do, the chlorine ions released during dissolving will be in a MUCH higher concentration than normal, in one tiny spot. Chlorine is the mortal enemy of stainless. Chlorine ions are one of the few things able to penetrate the passivated surface of the metal. Passivation is a protective oxide layer on the stainless, formed both by normal exposure to the environment (but very slowly and unevenly), and also by conscientious manufacturers who wish the user to get the maximum life of their products. Deliberate passivation is much thicker and more even.

Dissolving the salt in water (or whatever) greatly reduces the concentration of the ions, whether chlorine or sodium, at any spot on the metal, to the degree that the passivation is not affected.

(I used to make surgical equipment of stainless steel.)

Ray

[paulraphael]

Thanks, Ray.

If you do get a pit, is the metal their more vulnerable than the rest of the surface? I'd be bummed if it started to grow.

In the mean time, I guess I'll stop tossing salt onto vegetables that I'm roasting in a stainless pan.

[phatj]

Hm. I've always thrown salt into my stainless stockpots prior to adding water, and I never gave it a thought before now. The inside bottoms of the pots are a little discolored, maybe, but not pitted that I've noticed.

[budrichard]

I've read that you need to be careful with even high grade stainless steels and salt ... like don't salt the water until it's already simmering, so the salt goes right into solution rather than sitting on the bottom of the pan.

Any thoughts on this?

I roast mostly with clad metal pans, both with 18-10 stainless interiors. I don't want to pit them, and I'm wondering if salting the food in them before putting them into a 500 degree oven is an invitation to pitting.

I've noticed a small pit on the stainless interior of my favorite copper saucepan. No idea how it got there, but if possible I'd like to avoid getting any more.

←

Stainless Steel is what the name implies, it doesn't stain because of the alloying elements. Some stainless will rust but this is under the conditions of high humidity like if you put an item away damp and wait a long time. Personally, I don't worry at all about the stainless coatings on all my Falk cookware and have never found a pit. Certainly you can salt your food before putting your pans in the oven. Most of what you read about metalurgy on these Forums is from non-degreed individuals. -Dick

[Octaveman]

The only thing I do is wait for the water for pasta to come to a rolling boil before adding a little salt.

[Marlene]

If you're using kosher salt, and stir it when it hits the water while it's heating up, it should dissolve pretty quickly. I've never had a problem with my stainless steel pots and I salt my water all the time.

[ray goud]

I've read that you need to be careful with even high grade stainless steels and salt ... like don't salt the water until it's already simmering, so the salt goes right into solution rather than sitting on the bottom of the pan.

Any thoughts on this?

I roast mostly with clad metal pans, both with 18-10 stainless interiors. I don't want to pit them, and I'm wondering if salting the food in them before putting them into a 500 degree oven is an invitation to pitting.

I've noticed a small pit on the stainless interior of my favorite copper saucepan. No idea how it got there, but if possible I'd like to avoid getting any more.

←

Stainless Steel is what the name implies, it doesn't stain because of the alloying elements. Some stainless will rust but this is under the conditions of high humidity like if you put an item away damp and wait a long time. Personally, I don't worry at all about the stainless coatings on all my Falk cookware and have never found a pit. Certainly you can salt your food before putting your pans in the oven. Most of what you read about metalurgy on these Forums is from non-degreed individuals. -Dick

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Non-degreed does not mean inexperienced or unlearned.

Stainless steel stains less, that's where the name comes from. If it was stain free, it would be called stainfree or stainproof. I can tell you the exact procedure for making a stainless surface passivated. I have passivated thousands of stainless objects, and have seen hundreds which had their passive surface damaged through neglect or misuse. Any damage in the passive surface, from a nick or even a scratch/smear from an iron-bearing object will defeat the passive nature and potentially cause corrosion. The alloying elements tend to improve the corrosion protection as they increase in their percentage, which is mostly imparted courtesy of the chromium in the mix. The most corrosion resistant alloy is 316L, which is almost exclusively used in surgical devices.

Paulraphael was talking about leaving salt crystals intact on his pan. Yes, that spot with the pit will be more vulnerable to more corrosion. I don't know where you might get nitric acid to re-passivate the stainless, but it probably doesn't matter because you must treat it first with other acids, and that's quite dangerous outside of a controlled environment.

Salting the water greatly reduces the concentration of the chlorine ions and is of no practical concern. General use in the kitchen is usually not dangerous to stainless pans. To be sure you aren't being destructive, use a SS scrub pad instead of the soap-bearing (and rust-prone) regular steel scrub pads, when you need to.

[budrichard]

"I can tell you the exact procedure for making a stainless surface passivated. I have passivated thousands of stainless objects, and have seen hundreds which had their passive surface damaged through neglect or misuse."

I for one would be very interested in how one 'passivates' a stainless steel pan or one lined with stainless steel? -Dick

Edited April 18, 2007 by budrichard (log)

[phatj]

"I can tell you the exact procedure for making a stainless surface passivated. I have passivated thousands of stainless objects, and have seen hundreds which had their passive surface damaged through neglect or misuse."

I for one would be very interested in how one 'passivates' a stainless steel pan or one lined with stainless steel? -Dick

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Per Wikipedia, passivation is the natural formation of an air- and water-proof chromium oxide layer on the surface of stainless steels.

[ray goud]

"I can tell you the exact procedure for making a stainless surface passivated. I have passivated thousands of stainless objects, and have seen hundreds which had their passive surface damaged through neglect or misuse."

I for one would be very interested in how one 'passivates' a stainless steel pan or one lined with stainless steel? -Dick

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Please note that this is an industrial process and not to be undertaken without proper safeguards for personal safety.

First the object must be cleaned of all foreign substances (oil, grease, polishing compounds, slag, stains, etc.) by immersion in a heated industrial cleaner (Oakite 40, etc.), for as long as required to reach a cleaned surface. Rinsing to remove the loosened and converted materials, and the cleaner, must be done next, several times. "Pickling" in a (dangerous) bath of heated acids (a 20% solution of hydrochloric acid and 20% solution of sulphuric acid) is next, for about twenty minutes with agitation at about 140 degrees F. Rinsing is next, then neutralizing the acid residues by immersing the SS object in a potassium hydroxide solution, then rinse again copiously. The "pickling" removes all iron molecules from the SS surface, whether they got there through manufacture or as part of the SS alloy, and cannot be skipped. What are left are chromium and nickel atoms. Next is actual passivation by immersion in a 140 degree 40% solution of nitric acid for another twenty minutes, with agitation. This forms the "oxide" layer. Rinse copiously. Neutralization is again done with the potassium hydroxide, then copious rinsing is the final step.

FYI -Wikipedia is correct in that passivation CAN occur naturally. But, it is unreliable and extremely thin and fragile. Only a deliberate passivation done chemically can be expected to be useful. Another reaction which CAN occur naturally is anodizing of aluminum, but it is much too unreliable when done by Mother Nature, and responsible manufacturers do it deliberately to protect their (aluminum) products.

An interesting side note is that industrial buffing/polishing of SS objects can give a passivated-like effect because the buffing/polishing compound smears the chromium/nickel atoms over the iron ones and protects the surface, somewhat. But it is not as good as passivation.

Ray

[budrichard]

Passivation has nothing to do with the original question! It is basically a process to be performed after manufacture.

The ability of stainless steels to withstand corrosion is due to the alloying elements dispersed throughout the matrix. Bringing up the subject has only clouded the issue for other readers. Stainless steels in use don't have to be re-passivated and the use of salt or most corrosive agents will not cause a short term effect. Certainly, one could line the bottom of a stainless steel pot/pan with salt and there would be no effects for a long time. The use of salt in cooking has NO effect on the stainless lining. The introduction of this procedure in this thread is an example of my previous statement whcih was apprently taken exception with and a procedure was mentioned in an attempt to show a knowledge level.

I would have no problem lining the bottom of one of my Falk pots with sodium chloride for a couple of days.

Salt and the way it is used is a non-issue in the use of stainless steel lined pots/pans.EOT-Dick

[paulraphael]

Salt and the way it is used is a non-issue in the use of stainless steel lined pots/pans.EOT-Dick

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I'm not convinced by this, based on experience and on what I've been reading. I've seen the occasional pit in good quality stainless that's never been abused. And every article I've found on 18/10 stainless alloys (and its cousins) warns against exposure to sodium chloride in high concentrations.

Passivation is an issue because chlorine bleach and sodium chloride remove it.

[MattJohnson]

Please note that this is an industrial process and not to be undertaken without proper safeguards for personal safety.

First the object must be cleaned of all foreign substances (oil, grease, polishing compounds, slag, stains, etc.) by immersion in a heated  industrial cleaner (Oakite 40, etc.), for as long as required to reach a cleaned surface. Rinsing to remove the loosened and converted materials, and the cleaner, must be done next, several times. "Pickling" in a (dangerous) bath of heated acids (a 20% solution of hydrochloric acid and 20% solution of sulphuric acid) is next, for about twenty minutes with agitation at about 140 degrees F. Rinsing is next, then neutralizing the acid residues by immersing the SS object in a potassium hydroxide solution, then rinse again copiously. The "pickling" removes all iron molecules from the SS surface, whether they got there through manufacture or as part of the SS alloy, and cannot be skipped. What are left are chromium and nickel atoms. Next is actual passivation by immersion in a 140 degree 40% solution of nitric acid for another twenty minutes, with agitation. This forms the "oxide" layer. Rinse copiously. Neutralization is again done with the potassium hydroxide, then copious rinsing is the final step.

FYI -Wikipedia is correct in that passivation CAN occur naturally. But, it is unreliable and extremely thin and fragile. Only a deliberate passivation done chemically can be expected to be useful. Another reaction which CAN occur naturally is anodizing of aluminum, but it is much too unreliable when done by Mother Nature, and responsible manufacturers do it deliberately to protect their (aluminum) products.

An interesting side note is that industrial buffing/polishing of SS objects can give a passivated-like effect because the buffing/polishing compound smears the chromium/nickel atoms over the iron ones and protects the surface, somewhat. But it is not as good as passivation.

Ray

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Maybe I'll give this a go this weekend!

[ray goud]

Please note that this is an industrial process and not to be undertaken without proper safeguards for personal safety.

First the object must be cleaned of all foreign substances (oil, grease, polishing compounds, slag, stains, etc.) by immersion in a heated  industrial cleaner (Oakite 40, etc.), for as long as required to reach a cleaned surface. Rinsing to remove the loosened and converted materials, and the cleaner, must be done next, several times. "Pickling" in a (dangerous) bath of heated acids (a 20% solution of hydrochloric acid and 20% solution of sulphuric acid) is next, for about twenty minutes with agitation at about 140 degrees F. Rinsing is next, then neutralizing the acid residues by immersing the SS object in a potassium hydroxide solution, then rinse again copiously. The "pickling" removes all iron molecules from the SS surface, whether they got there through manufacture or as part of the SS alloy, and cannot be skipped. What are left are chromium and nickel atoms. Next is actual passivation by immersion in a 140 degree 40% solution of nitric acid for another twenty minutes, with agitation. This forms the "oxide" layer. Rinse copiously. Neutralization is again done with the potassium hydroxide, then copious rinsing is the final step.

FYI -Wikipedia is correct in that passivation CAN occur naturally. But, it is unreliable and extremely thin and fragile. Only a deliberate passivation done chemically can be expected to be useful. Another reaction which CAN occur naturally is anodizing of aluminum, but it is much too unreliable when done by Mother Nature, and responsible manufacturers do it deliberately to protect their (aluminum) products.

An interesting side note is that industrial buffing/polishing of SS objects can give a passivated-like effect because the buffing/polishing compound smears the chromium/nickel atoms over the iron ones and protects the surface, somewhat. But it is not as good as passivation.

Ray

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Maybe I'll give this a go this weekend!

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I must caution you to be very careful!!! The acid fumes are extremely dangerous!! Don't even try it unless you have complete ability to evacuate the fumes. Do you have means to protect against acid splashing? Do you have experience in mixing and diluting acids? The base is equally as dangerous as the acids. And why are you going to try it, anyway?

[ray goud]

Passivation has nothing to do with the original question! It is basically a process to be performed after manufacture.

The ability of stainless steels to withstand corrosion is due to the alloying elements dispersed throughout the matrix. Bringing up the subject has only clouded the issue for other readers. Stainless steels in use don't have to be re-passivated and the use of salt or most corrosive agents will not cause a short term effect. Certainly, one could line the bottom of a stainless steel pot/pan with salt and there would be no effects for a long time. The use of salt in cooking has NO effect on the stainless lining. The introduction of this procedure in this thread is an example of my previous statement whcih was apprently taken exception with and a procedure was mentioned in an attempt to show a knowledge level.

I would have no problem lining the bottom of one of my Falk pots with sodium chloride for a couple of days.

Salt and the way it is used is a non-issue in the use of stainless steel lined pots/pans.EOT-Dick

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WRONG

[paulraphael]

there's a recipe for passivation with citric acid and edta (tetrasoidium salt) here:

http://www.thefabricator.com/TubePipeProdu...icle.cfm?ID=888

these are both lurking in my darkroom boxes somewhere. seems like a safer procedure.

what i'm curiuos about is this: passivation is supposed to occur spontaneously with 18-10 steel in the presence of oxygen. does chloride corrosion somehow stop this process from occuring (after the salt and water are washed away)? if not, then it seems like chemical passivation would be unecessary.

[ray goud]

there's a recipe for passivation with citric acid and edta (tetrasoidium salt) here:

http://www.thefabricator.com/TubePipeProdu...icle.cfm?ID=888

these are both lurking in my darkroom boxes somewhere. seems like a safer procedure.

what i'm curiuos about is this: passivation is supposed to occur spontaneously with 18-10 steel in the presence of oxygen. does chloride corrosion somehow stop this process from occuring (after the salt and water are washed away)? if not, then it seems like chemical passivation would be unecessary.

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Again, "natural" environmental oxidation of a stainless steel surface is unreliable in the extreme. If it wasn't, there would be no need to passivate surgical instruments made of SS. The exact same situation exists for aluminum; natural oxidation causes an aluminum oxide layer to instantly form, but it is very fragile and unreliable. So the manufacturer uses an electically-induced anodic process to form a thick oxide layer. I mention this because more people are familiar with "anodized aluminum" than they are with passivated stainless. I am frequently at a loss as to why the makers never mention the passivation process. I try not to think that some might not use the process, just as I hope that lead is not in childrens' toys.

[paulraphael]

Ray,

what are the similarities/differences in the alloys used in surgical instruments and 18-10 steel?

And what do you think of the citric acid/edta process? if I have a pan that already has a salt pit or two, would it make sense to try something like this? Would there be any risk of damage (to pan, self, or planet)?

[MattJohnson]

Please note that this is an industrial process and not to be undertaken without proper safeguards for personal safety.

First the object must be cleaned of all foreign substances (oil, grease, polishing compounds, slag, stains, etc.) by immersion in a heated  industrial cleaner (Oakite 40, etc.), for as long as required to reach a cleaned surface. Rinsing to remove the loosened and converted materials, and the cleaner, must be done next, several times. "Pickling" in a (dangerous) bath of heated acids (a 20% solution of hydrochloric acid and 20% solution of sulphuric acid) is next, for about twenty minutes with agitation at about 140 degrees F. Rinsing is next, then neutralizing the acid residues by immersing the SS object in a potassium hydroxide solution, then rinse again copiously. The "pickling" removes all iron molecules from the SS surface, whether they got there through manufacture or as part of the SS alloy, and cannot be skipped. What are left are chromium and nickel atoms. Next is actual passivation by immersion in a 140 degree 40% solution of nitric acid for another twenty minutes, with agitation. This forms the "oxide" layer. Rinse copiously. Neutralization is again done with the potassium hydroxide, then copious rinsing is the final step.

FYI -Wikipedia is correct in that passivation CAN occur naturally. But, it is unreliable and extremely thin and fragile. Only a deliberate passivation done chemically can be expected to be useful. Another reaction which CAN occur naturally is anodizing of aluminum, but it is much too unreliable when done by Mother Nature, and responsible manufacturers do it deliberately to protect their (aluminum) products.

An interesting side note is that industrial buffing/polishing of SS objects can give a passivated-like effect because the buffing/polishing compound smears the chromium/nickel atoms over the iron ones and protects the surface, somewhat. But it is not as good as passivation.

Ray

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Maybe I'll give this a go this weekend!

←

I must caution you to be very careful!!! The acid fumes are extremely dangerous!! Don't even try it unless you have complete ability to evacuate the fumes. Do you have means to protect against acid splashing? Do you have experience in mixing and diluting acids? The base is equally as dangerous as the acids. And why are you going to try it, anyway?

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I meant it as sarcasm. there wasn't a sarcastic enough emoticon i guess. Theres no way I'd ever try that! I'd rather have pitted stainless steel than risk all the harm I could do to myself with that process.

[ray goud]

Ray,

what are the similarities/differences in the alloys used in surgical instruments and 18-10 steel?

And what do you think of the citric acid/edta process? if I have a pan that already has a salt pit or two, would it make sense to try something like this? Would there be any risk of damage (to pan, self, or planet)?

←

18-10 stainless steel is only a general term. It means that the maker could have used a number of alloys which had a chromium/nickel content in the range of 18 % and 10 %, respectively. What is more important is the AISI type designation, and surgical instruments are mostly made from type 304, type 304L, type 316, and type 316L varieties. That AISI range I just listed increases in corrosion resistance from lower to higher. In general, more chromium and more nickel are better. The types with suffix "L" mean there is less carbon in the mix, leading to more corrosion resistance. SS used for non-surgical cutlery is an entirely different kettle of fish.

[ray goud]

Ray,

what are the similarities/differences in the alloys used in surgical instruments and 18-10 steel?

And what do you think of the citric acid/edta process? if I have a pan that already has a salt pit or two, would it make sense to try something like this? Would there be any risk of damage (to pan, self, or planet)?

←

18-10 stainless steel is only a general term. It means that the maker could have used a number of alloys which had a chromium/nickel content in the range of 18 % and 10 %, respectively. What is more important is the AISI type designation, and surgical instruments are mostly made from type 304, type 304L, type 316, and type 316L varieties. That AISI range I just listed increases in corrosion resistance from lower to higher. In general, more chromium and more nickel are better. The types with suffix "L" mean there is less carbon in the mix, leading to more corrosion resistance. SS used for non-surgical cutlery is an entirely different kettle of fish.

Sorry, but I forgot the second part of your question:

I would ignore the existing pits and live with them. I would not attempt passivation in a home environment.

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