descaling question / bad results?

[dfluke]

I recently purchased a bonavita electric kettle, and of course, after a while using it, it started to become gross on the bottom, so I descaled it. I put in a package of urnex dezcal and put in about 4 cups of water (which is what it can hold, but which also proved to be too much).
So after I cleaned it up, I was left with this blotch in the bottom.

Did I do something wrong? Is this normal? I did stir in the powder a bit before running the cycle but the only thing I can think of is that it sat on the bottom.
The performance of the kettle isn't diminished, it just looks weird.

I've attached a photo.

Anyone have any advice?

[Ray T]

Kind of looks like the urnex  didn't remove all the gunk ?? Doesn't look etched

[tyme]

Is that Stainless or Aluminum?

[Tex]

I've seen stainless steel espresso filter baskets turn completely black after descaling with Dezcal. Since the main descaling agent in Dezcal is citric acid, and I know it doesn't cause blackening, I'd be suspicious of the other ingredients. Try a plain citric acid solution and see if it removes the stain?

Which begs the question; Are you using filtered water to begin with? My whole house is softened with salt and my coffee nook uses a cation potassium system - zero scale problems in my gear!

[MMW]

If it's stainless maybe try warming a little vinegar in it and swirling it around?

[BoldJava]

I've seen stainless steel espresso filter baskets turn completely black after descaling with Dezcal. Since the main descaling agent in Dezcal is citric acid, and I know it doesn't cause blackening, I'd be suspicious of the other ingredients. .  .

From the MSDS:
Material CAS# LD-50-LC50 Mixture: LD50 (oral rat)
Citric Acid 77-92-9 5500 mg/kg
Aluminum Sulfate 10043-01-3 N/A
Sulfamic Acid 5329-14-6 3160 mg/kg

http://www.cw-usa.com/common/images/other/dezcal-msds.pdf

[dfluke]

This is what I have:
http://bona-vita.biz/products/kettle2.asp

It says that it's stainless steel.

I am using a very basic 2 stage under the sink filtration system for the water. It's one they sell at sears, a kenmore brand I believe.  I doubt that it's as good as what a coffee shop would have, but it does pretty well.

I'm just not familiar with chemicals and descaling agents and figured I did something wrong. I tried wiping it out, but that didn't work.
I'll have to purchase some vinegar to try.

[dfluke]

Kind of looks like the urnex  didn't remove all the gunk ?? Doesn't look etched

That spot wasn't there when I started. I had a little ring around the outside portion where the element probably lies under the kettle. That spot was created when I put the dezcal in and turned it on.

[grinderz]

Just a hypothesis, but it sounds like where the stainless steel is close to the element that some metallurgical change occurs. Stainless steel has all kinds of other elements in it besides iron, namely chrome and nickel and sometimes other metals depending on properties desired in the steel. I bet if you looked it up, one of the components in your descaler reacts with some form of chrome or nickel.