6 Stains on Stainless Steel

Stains on Stainless Steel….

And how to remove them!

Struggling with stains on stainless steel cookware?  You’re not alone.  

While it sounds like an oxymoron, the truth is that stainless steel, while one of the hardiest and most durable cookware materials, is not immune to staining.   Here are the 6 most common stains on stainless steel that you can come across and how to get rid of them.  

Stain on Stainless Steel Cookware #1:

White Stains aka Water Stains aka Calcium Deposits

These are those white stains that just won’t scrub away.   Turns out, that white stuff  is calcium.  

Now you  might be wondering, how did Calcium get stuck onto my pans?  Here’s the thing: tap water, even if it is not hard water, tends to contain small amounts of calcium bicarbonate.  When water is boiled or food is cooked in that water, the water breaks down the bicarbonate into calcium carbonate (aka chalk or limescale!).  This is the hazy white stuff that is stuck to the bottom of your pans.  Here’s one of my pans with the all too familiar haze.

White stains on stainless steel Calcium deposit - stains on stainless steel

Calcium carbonate doesn’t dissolve easily in water which is why soap and water will not remove the deposits.   It’s also not soluble in oil, which is why it remains stuck even after cooking with oil in the pan.  

Are the white deposits on stainless steel harmful?

No.  It’s a normal and harmless buildup on your pans and other than discolouring and affecting the aesthetics, is not cause for any concern.   

How to remove white calcium deposits on your stainless steel pans?

Calcium carbonate dissolves in acidic mediums so you need something like vinegar and water or a product like Bar Keepers Friend (which is a mild oxalic acid) which will dissolve away the calcium deposits, leaving you a shiny pan.    

In the case of my pan, I added ⅓ cup water and ⅓ cup white vinegar to the pan and warmed the mixture for a few minutes.

Then, I discarded the liquid, washed and wiped. Viola!  The pan is quite shiny and there is no fine white haze.

shiny stainless steel pan

Stain on Stainless Steel Cookware #2

Pitting

A few days ago my husband left a stainless steel saucepan of water boiling on the stove well past the point of complete evaporation!  The result?  A pan with small discolored dots on the bottom that just won’t come off.  

pitting stains on stainless steel pan pitting stains on stainless steel

I realized that we are now the proud owners of … a pitted pan!

What is pitting?

Pitting is technically not a stain but an erosion of the surface of the metal.  Pitting on stainless steel occurs in the presence of chlorides, like salt.  So clearly, the tap water that was boiling in our pot had some salt dissolved in it which went on to create pitting once all the water was gone.  

I’m going to go into deeper detail for those interested in a more scientific explanation, myself included!  The reason why stainless steel is resistant to corrosion is because it contains chromium.  Chromium reacts with oxygen in the air to form a thin layer of chromium oxide on the surface.  It is this layer of chromium oxide that  makes stainless steel passive and protects the steel from reacting with oxygen and rusting.

Now I’ve been boiling salted water (for pasta, rice etc) for years so I know that salted water normally doesn’t damage stainless steel.  However, when undissolved salt is added to a stainless steel pot (or water boiled dry, as in my case) the chloride in the salt can attack the passive layer of chromium oxide, leaving pockmarks where it removes the oxide.

Can you remove pitting stains?

According to hunker.com, yes, by grinding out the pitted and/or rusted parts and being careful how you use it in the future (ie.avoid prolonged exposure to salty water, vinegar etc) so that it doesn’t pit again.

For most of us who are not willing or able to grind a pan, I would say, no.  Once your stainless steel pan is pitted, it’s pitted.  

Is it safe to use a pitted pan?

Now if you’ve read my my article on stainless steel cookware, or if you’ve spent any time researching stainless steel you would know that it does leach small quantities of nickel and chromium into food. For most of us, the amounts are not significant and by and large, stainless steel is considered a safe material for cookware.  

According to most accounts, a pitted pan is still safe to use and will not lose its function though of course, it won’t look as good as before.  The chromium in the stainless steel would already have formed a new layer of chromium oxide layer over the pits and in theory, your pot is as corrosion resistant as before.

Others, however, warn that a heavily scratched and pitted pot will leach more of these metals and you should dispose of them.  Personally, I am going to toss my pitted stainless steel sauce pan, I don’t want to take the chance.  

So in the end, the choice is really yours.  

 

Stain on Stainless Steel Cookware #3

Rust

Yes, that’s right, rust. Stainless steel by its nature is corrosion resistant.  But not corrosion proof and sometimes it does rust.  If you are wondering what would make stainless steel rust, I’ve talked about it in my article here.

Two questions come to mind:

  1. How to remove rust spots from stainless steel pans; and
  2. Is a rusty pan safe to use?

How to remove rust spots from stainless steel pans

If you see a bit of rust on a stainless steel pan, your first instinct should be to reach for a pad of good old SOS steel wool, right?

WRONG!   

The first thing to do is to avoid using any steel wool, hard metal brushes or abrasive cleaners on your stainless steel pan.  These will make the pan even more susceptible to corrosion.

There are couple of options. If you want to go the natural route, make a thick paste of baking soda with water and cover the rusted portions.  Use a toothbrush, plastic scrubby or soft cloth to  rub the mixture onto the rust.  The rust should come right off.  

Another option is to use Bar Keepers Friend which works just as well.   

Is a rusty pan safe to use?

According to the experts at the  University of Illinois at Urbana-Champaign, bit of rust is not harmful and is quite benign in small quantities. Rust is basically oxidized iron and is only harmful if your body is unable to remove iron effectively.   

Having said that, you don’t want to be consuming large amounts of it, so make sure you follow the above steps to make sure the rust has been cleaned off the pan before you use it again.  

Personally, however, I would avoid using a pan that shows signs of rusting. In my opinion, a pan once rusted is always going to be susceptible to rusting again, even if you remove all the corrosion. Also, I prefer to play it safe.   In this article at prevention.com, toxicologist James H. Woods, PhD, of the department of environmental and occupational health sciences at University of Washington says that while he is not aware of any health issues related to eating food made in rusted pans, why would you take the risk?  He recommends buying new cookware.

So do I.  

 

Stain on Stainless Steel Cookware #4

Heat Tint

If you’re familiar with heat tint, it’s that ugly rainbow-like discolouration on your stainless steel pan caused by excessive heat or by heating a pan too quickly.  It doesn’t affect the performance of the pan nor the foods cooked in the pan.  Just the aesthetics.  To be honest, most of my stainless steel pieces look like they are heat tinted and I can’t say it has really ever bothered me much.

What exactly causes heat tint?

Stainless Steel is an alloy of metals including iron, carbon, chromium and nickel (you can read more about SS here). The chromium in the steel combines with oxygen in the air to form a thin, invisible layer of chromium oxide which makes the material passive and prevents the air from further reacting with the metals.  

Now, when stainless steel is heated, the oxidation increases and the top layer becomes thicker.  As the layer becomes thicker, the wavelength of light that it reflects changes and hence we see a range of colours. As the temperature increases over time, the oxidation increases and the colors change, usually in a range from yellowish to blue.  

How to remove heat tint?

It seems you can use Bar Keepers Friend for just about anything to do with Stainless Steel.  Heat tint can be cleaned with a bit of BFK and some tlc.  Alternatively, a mixture of white vinegar and water also works just fine.    

 

Stain on Stainless Steel #5:

Burnt Food

Ah, this is by far my favorite (not!).  But definitely the one I have the most experience with.  If you’ve even been tempted to just throw out a SS pan with stubborn burnt on food, you’re not alone.  I’ll go as far as to admit that I once might actually have thrown out a perfectly good SS frying pan for that very reason!

The more interesting question, however, is how to clean stainless steel cookware that is burnt.  I find that baking soda works quite well. Cover the base of the pot with water and sprinkle it generously with baking soda.  Let sit for at least 30 minutes.  Scrub it off gently with a plastic scrubber.  For really bad burns, leave it in for longer.  

Another option of course is Bar Keepers Friend.  Here’s an awesome video that shows how effective this wonder cleaner is for removing scorch stains from a pan.  The pan in the video is an enamel pan but the principle remains:

Last but not least:

 

Stain on Stainless Steel #6 :

Black or Grey Residue on New Stainless Steel Cookware

Now this is an odd one and one I haven’t experienced myself.  But I’ve seen a lot of queries about it so it was warranted some deeper research.  

Here’s what quite a few users have experienced: They buy a new set of SS cookware and as expected, wash it with warm soapy water before the first use.  All good so far.  Then comes time to wipe the inside and they find black or grey residue coming off on the paper towel.  

The interesting thing is, the residue is still there after multiple washes and cleanings.  

What is the black residue on new stainless steel cookware?

When SS cookware is made, a mechanical polishing process using very fine abrasives is used to make it shiny.  Sometimes this process leaves a residue that cannot be removed by hand or dishwashing.

How to remove the black residue?

Here’s what KitchenAid recommends: spread a small amount of olive oil on the inside of the pan. Let it sit and then wipe the oil out.  After that, proceed to wash with dish soap and hot water.  

Other recommendations are to gently scrub using a mixture of lemon juice and salt and then wash.  

Some SS cookware comes with instructions to scrub it gently with a 1:1 mix of baking soda and warm water before using the pans.  

 

Some final words of caution:

So there you have it – the most common stains on stainless steel and how to remedy them.  While it seems that some stains on stainless steel cookware are inevitable, here are some final words of caution:

  1. Don’t use oven cleaner on your cookware as it can be abrasive.  
  2. Don’t use chlorine based cleaners like Comet and Ajax as chlorine is corrosive on SS.  Use acid based cleaners like  Bar Keepers Friend or plain white vinegar.
  3. Likewise, don’t bleach your cookware with chlorine bleach.  
  4. Avoid the use of abrasive steel wool. That strips the protective top layer of chromium oxide and makes your pan susceptible to corrosion and rust.  A plastic scrubby is recommended.
  5. When adding salt to boiling water, bring the water to a rolling boil before adding salt and stir well.  This prevents the pan from pitting.

 

Happy Cooking!

 

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