Well, my one attempt to remove the scale with straight muriatic and a few drops of surfactant failed, but the laundry basin is now a brilliant white
I did however discover that in diluted form it is exceptionally well able to remove petrified fingerprints, much better than white vinegar and Tergitol, and even the enzyme based Sporicidin.
I diluted it to about 5-7% hcl with distilled water, adding a fairly high concentration of Tergitol blend (s3 and s9) to make a powerful cleaning solvent. Sprayed over the dusty record and allowed to soak for 5 mins, then rinsed off without scrubbing or steaming seems to boost the level of clean the subsequent stages produce. Undamaged records are now dead quiet even in the lead in grooves where most fingerprints are found.
This has become my new first step in the wash process. There doesn't seem to be any harm being done to the record, and the results are substantial enough to carry on with it.