How to clean “reddish/ brownish” grime/ deposit marks from the edge of a Zojirushi Water Boiler

Question

I have an older version of one of these: https://www.zojirushi.com/app/product/cvdcc

For taking care of them, the standard procedure is to run them in "cleaning mode" with a full tank of water with a packet of Citric Acid dissolved. That works really well for removing the mineral deposits from inside the tank.

Recently, I noticed that there was rust-looking stuff coming out from the upper lid, so I replaced the upper lid. However, the deposit is still there on the edge where the lid touches the tank.

The standard procedure of descaling them doesn't work here because you are not supposed to fill the water that high in the tank. How can I descale this? I imagined that the lightweight version of a full descaling process would be something like wiping the edge with a paper towel soaked in lemon juice, but that didn't do anything.

This is what it looks like:

(click image to embiggen.)

Answer 1

As citric acid and prob vinegar don't work in this case, I would buy a descaler gel or liquid descaler instead of powder, that you can apply on the spot, to let it soak and wipe off. This does the trick for the lid of my kettle.

As the scale is brownish, I would probably make sure, that it is scale and not rust or a combination. If you are unsure, I would combine acid like lemon juice or vinegar with baking powder. This will create a foaming paste, that you can apply on the spot and should get rid of it. Works also well for oven trays.

Answer 2

I contacted Zojirushi customer support, and got this:

"... We would recommend to clean the staining with a soft toothbrush and toothpaste. ..."

Answer 3

Very likely rust. If it really bothers you , I would remove it mechanically with sand paper like 400 grit wet-or-dry. At greater expense , a commercial cooking supply store likely has cleaners used on commercial equipment.