hankbates wrote:Calcium citrate is relatively insoluble and has a tendency to plug small passages.
Calcium acetate is quite soluble and does not have this problem.
rpavlis said that the only problem with using vinegar is its tendency to make the coffee taste like a salad if not thoroughly removed.
Vinegar has the advantage that it's also is a weaker acid than citric, and if you use white vinegar (5% acetic acid) you have a relatively tame and safe concentration. It will take more time but that's an advantage if you are keeping an eye on it when soaking chrome or nickel plated parts. Either will work faster if the bath is hot.
Full strength white vinegar (5%, about 0.8 Molar acetic acid) is quite a bit less acidic than citric at 1 tablespoon per liter, even though the latter is only about a 0.1 Molar solution. Difference in initial pH would be about 2.4 for the vinegar and about 2.1 for the citric. That may not look like much, but because pH is a log scale it means the citric has over twice the concentration of [H⁺] ions. The citric would work faster and be more corrosive, but would dissolve less scale before it was neutralized (you may need to change to fresh descaling solution more often.)
Having said all that, I should mention that Paul Pratt, who has maybe been there and done that more than anyone, says he uses citric to descale disassembled parts, and sometimes tries both sulfamic and citric on tough jobs.¹ Sulfamic is a far stronger acid than citric,², so you would need to be extra cautious - best to use a commercial descaler per instructions for that.¹
per Faema E61 Legend Scale²
Sulfamic 1.1 (almost a strong acid)
Citric (I) 3.1