Sulfamic acid is another of the more commonly used cleaning / descaling
agent that is typically used on ceramics/porcelain and metals.
It is a lot weaker than sulfuric acid but still is an acid. Your coffee
pot should be safe but again, Id not recommend letting it soak overnight
in the stuff. If you have a lot of scale to remove it's best to do a
few shorter runs than one long hard run of descaler.
If I am not mistaken, this stuff is used in the manufacturing of
artificial sweeteners too and in some other medical purposes.