Stainless steel corrosion, safe?

[Dem93]

Hey everyone, I hope the question is not off topic.

A few days ago I made a saline solution (45g salt and 180ml of tap water) in a stainless steel pan. This solution was boiled to dissolve the salt and used to add a specific amount of salt to a beer I made, a german style that is traditionally made with salty water. While I was dosing the salt in each bottle I noticed that the solution had turned sligh yellowish, but at first I assumed it was just some salt impurity. However, a few hours after bottling I came back to wash the pan and realized the salt had started to corrode the bottom, and at that point there was some stuff floating and visible areas of corrosion. Now, since I dosed 2-3ml of this solution in each bottle (not all of them though), is this of any health concern? Is it just iron?

I used a magnet and it was attracted by the pan, so I guess it is not AISI 312 but rather some ferritic type of stainless steel (it's a cheap pan, single wall thin metal).

Thanks to everyone, and please remove if off topic

 

[exchemist]

25 minutes ago, Dem93 said:

Hey everyone, I hope the question is not off topic.

A few days ago I made a saline solution (45g salt and 180ml of tap water) in a stainless steel pan. This solution was boiled to dissolve the salt and used to add a specific amount of salt to a beer I made, a german style that is traditionally made with salty water. While I was dosing the salt in each bottle I noticed that the solution had turned sligh yellowish, but at first I assumed it was just some salt impurity. However, a few hours after bottling I came back to wash the pan and realized the salt had started to corrode the bottom, and at that point there was some stuff floating and visible areas of corrosion. Now, since I dosed 2-3ml of this solution in each bottle (not all of them though), is this of any health concern? Is it just iron?

I used a magnet and it was attracted by the pan, so I guess it is not AISI 312 but rather some ferritic type of stainless steel (it's a cheap pan, single wall thin metal).

Thanks to everyone, and please remove if off topic

 

A yellowish tinge would be consistent with iron, certainly. I would not expect any health concerns. Iron itself is not a problem and I would have thought the makers of cooking pans would avoid any alloy components that might give health issues if they were to leach out through corrosion.  The main other constituent of stainless steel is Cr. It seems to be Cr +6 that is hazardous, but the product of any corrosion due to salt (NaCl) will be lower oxidation states that are apparently not a problem. I found this link which may provide some reassurance:

https://bssa.org.uk/bssa_articles/does-the-chromium-in-stainless-steel-contain-chrome-6-cr6-and-is-this-a-potential-health-hazard/

[studiot]

1 hour ago, Dem93 said:

I used a magnet and it was attracted by the pan, so I guess it is not AISI 312 but rather some ferritic type of stainless steel (it's a cheap pan, single wall thin metal).

Thanks to everyone, and please remove if off topic

Welcome Dem.

Don't be worried about your question it's perfectly respectable question asked in a most reasonable way.
I only wish lots of others would take the same amount of trouble to pose their questions so clearly.

+1

In response I would say that the magnetic effect shos that the steel contains (nearly) no nickel which could make it a very poor stainless, particularly if the chrome content is also low.

Here is a good writeup of saucepan stainless steels.

Does the magnetic bit extend to the sides as well as the bottom ?

https://www.rebeccawood.com/health/cookware/a-buyers-guide-to-stainless-steel-cookware/

[John Cuthber]

I wouldn't like to have to rule out Cr(VI) as the cause of the yellow colour.

How important is the beer?

[exchemist]

7 minutes ago, John Cuthber said:

I wouldn't like to have to rule out Cr(VI) as the cause of the yellow colour.

How important is the beer?

Yeah but how are you going to get Cr (0) up to Cr(+6) without a strong oxidising agent? Salt water and a bit of atmospheric oxygen is never going to do that, surely, is it? 

[John Cuthber]

Air is a good enough oxidant. I can imagine either magnesium carbonate or sodium ferrocyanide acting as a catalyst.

 

 

[Sensei]

@Dem93

I would try to use distilled water instead of tap water, the next time you will be preparing and boiling saline solution in your stainless steel pan, to see if it makes any difference. Don't change anything in your procedure except replace tap water by distilled water.

Water can be fluoridated and/or chlorinated in some countries:

https://en.wikipedia.org/wiki/Water_fluoridation_by_country

https://en.wikipedia.org/wiki/Water_chlorination

additionally it may contain unexpected elements ("water hardness"), such as Ca²⁺, Mg²⁺

https://en.wikipedia.org/wiki/Hard_water

 

Additionally, in some countries salt is iodized:

https://en.wikipedia.org/wiki/Iodised_salt

Sea salt contains much more elements than just NaCl:

https://en.wikipedia.org/wiki/Sea_salt

15% are impurities.

 

Edited May 29, 2021 by Sensei

[exchemist]

1 hour ago, John Cuthber said:

Air is a good enough oxidant. I can imagine either magnesium carbonate or sodium ferrocyanide acting as a catalyst.

 

 

Well we can rule out the latter in this context, but some MgCO₃ could be present in hard water I suppose. Does that mean you discount the reassurance given in the link in my first post on this thread? 

[Dem93]

Thanks to everyone for your answers, as always things are more complicated than they seem! 
 

5 hours ago, studiot said:

Does the magnetic bit extend to the sides as well as the bottom ?

https://www.rebeccawood.com/health/cookware/a-buyers-guide-to-stainless-steel-cookware/

Thank you for your kind welcoming!
Yes, it is a single layer of steel
 

 

4 hours ago, John Cuthber said:

I wouldn't like to have to rule out Cr(VI) as the cause of the yellow colour.

How important is the beer?

Luckily I didn't add it to all the bottles, but I'd say to a third of them.
However as I said at the time of bottling this colour change\reaction wasn't that obvious, it was only when I cleaned it hours later. To play it safe I could dump them and change my procedure next time (using glass I guess) even though that would be a shame  

2 hours ago, Sensei said:

@Dem93

I would try to use distilled water instead of tap water, the next time you will be preparing and boiling saline solution in your stainless steel pan, to see if it makes any difference. Don't change anything in your procedure except replace tap water by distilled water.

Water can be fluoridated and/or chlorinated in some countries:

 

Unfortunately in Italy where I'm from it seems almost impossible to find drinkable distilled water. The only type you can find is the one used for ironing or for such appliances and it specifically says it's not for consumption. I've been looking into it because I'm also passionate about tea and coffee and many people are experimenting with the so called "water recipes", starting from distilled and adding minerals in specific ampunts to create a good water profile.

And yes, my water has chlorine, but the smell seems to go away from the bottle in a little over a day, the water I used was decanted for a while, not straight from the tap, so I would say very little was left

6 hours ago, exchemist said:

A yellowish tinge would be consistent with iron, certainly. I would not expect any health concerns. Iron itself is not a problem and I would have thought the makers of cooking pans would avoid any alloy components that might give health issues if they were to leach out through corrosion.  The main other constituent of stainless steel is Cr. It seems to be Cr +6 that is hazardous, but the product of any corrosion due to salt (NaCl) will be lower oxidation states that are apparently not a problem. I found this link which may provide some reassurance:

https://bssa.org.uk/bssa_articles/does-the-chromium-in-stainless-steel-contain-chrome-6-cr6-and-is-this-a-potential-health-hazard/

Thanks, this is interesting information!

 

[John Cuthber]

17 hours ago, exchemist said:

Well we can rule out the latter in this context,

How?

[exchemist]

2 hours ago, John Cuthber said:

How?

We have a stainless steel cooking pot, some salt and some water. Where would ferricyanide come from? 

[John Cuthber]

18 hours ago, exchemist said:

Where would ferricyanide come from? 

As an anti-caking agent in salt.

It's not the only one used. That's why I also motioned MgCO₃

[exchemist]

35 minutes ago, John Cuthber said:

As an anti-caking agent in salt.

It's not the only one used. That's why I also motioned MgCO₃

Aha, that's interesting. But this must be a universal issue, then, in cooking with stainless steel vessels, since salt is an essential ingredient in cooking almost anything. Why are we not all poisoned?  

[John Cuthber]

 

32 minutes ago, exchemist said:

Why are we not all poisoned?  

On 5/29/2021 at 3:23 PM, Dem93 said:

(45g salt and 180ml of tap water)

Is not a common recipe

[Dem93]

3 hours ago, John Cuthber said:

As an anti-caking agent in salt.

It's not the only one used. That's why I also motioned MgCO₃

I don't think salt sold in Italy has anti-caking agents, it should state it in the ingredients list, but I can't be 100% sure of course. But yeah, I remember many salt brands used it when I lived in the UK, which surprised me because I had never seen it before.

And true, it is a crazy amount of salt in so little water. Next time I'll be making such a concentrated salt solution I'll make sure to use glass. An excuse to buy those fancy lab-grade borosilicate glass beakers/flasks. So I can say it has a purpose other than looking cool  

[exchemist]

4 hours ago, John Cuthber said:

 

Is not a common recipe

That's a fair point, certainly. 

[studiot]

6 hours ago, John Cuthber said:

As an anti-caking agent in salt.

It's not the only one used. That's why I also motioned MgCO₃

This can be true, but there's salt and then again there's salt.

At home, we use sea salt for cooking and other culinary purposes.

Looking at the label it says that the fine sea salt (table grade) contains added sodium hexacyanoferrate (II) as an anti-caking agent.

The coarse granules meant for a grinder do not.

Of course sea salt contains iodates (which are famous for yellow staining) and many other compounds.

We have never experienced this yellow colour with any of our stainles pans - either those from Portugal or the UK.

Rock salt comes in similar grades, but does not include the range of additional minerals that sea salt does.

Some manufaturers artificially add iodine to rock salt to emulate the composition of sea salt.

[MigL]

6 hours ago, Dem93 said:

I don't think salt sold in Italy has anti-caking agents, it should state it in the ingredients list

Why don't you post the ingredients list of the salt you used, so we can possibly eliminate the salt as the source of the discoloration ?

Better yet, why not be a good Italian, and stick to 'vino', rather than craft beers.
I recommend a nice, and very drinkable, Aglianico from the Irpinia ( Campania ) region.

[Oliver D.]

On 5/31/2021 at 7:38 AM, John Cuthber said:

 

Is not a common recipe

Would they still react with a lower concentration? At least theoretically?

[John Cuthber]

7 hours ago, Oliver D. said:

Would they still react with a lower concentration? At least theoretically?

What do you mean by "react"?