I have used for Por-15 with good results. My preference is to descale the tank and then have it acid dipped. Then run the fuel tank clean and follow regular winter procedures.
Peter you are quite right but there are situations where it's is not really practicable, one of mine that I used sealer in is a genuine Manx tank that had become porous on some of the welds, without cutting the entire tank open it would have been impossible, another is a Brough Superior tank which are soldered tin sheet, too far gone to be plated and again the only way to be able to use it other than completely dismember it, and probably have to make a copy, is a sealer.I cannot really understand the need for fuel tank sealant, surely if you have a fuel tank leak you get it fixed, if you have rust or debris in the tank you clean it out as best you can and then put an inline fuel filter on the fuel pipe. I have never treated a Vincent tank with sealant in 55 years, I did once have a Tank weep fuel (long before ethanol) it must have had a poor weld around the steering column recess, once I had got rid of the fumes I had it welded and it never leaked again.
You should be using bicarbonate of soda not soda crystals. Bicarbonate is baking soda.Well I tried it for a day and I have just taken it off. The inside is as black as if it was powder coated I cant belive the corrosion on the + anode(diode?) easy with an old battery charger and a battery in series hardest part is finding Soda crystals plenty of them about but all dressed up in fancy names and prices,drain unblocker, wonder cleaner etc etc and who knows what else they have with them . Amazingly I found the base product as cheap as chips where I never go Tesco!
Now to dry it out and get some Slosh coated inside