An alternative to acid pickle is PHdown an swimming pool acid.
Cheap and it works.
PhDown, or similar products used for spas and swimming pools, is
usually sodium bisulphate, and it is indeed a superior product for
use as pickle. Chemically it's the same thing as products like
Sparex pickle, but it's usually purer, and often cheaper as well. It
IS important to understand that this is nevertheless, a sulphuric
acid salt. Not as dangerous as the acid itself of course, but still
quite capable of doing damage to things like clothing and benchtops,
etc. It's safety is the same as the commercial dry acid pickling
compounds sold to jewelers, like Sparex, which are the same
chemical. The advantages of the pool chemical over the commercial
pickles are just the purity of the pool chemical, the price (if lower
where you are), and perhaps availability if it's more easily found in