Keg Washing with Lye
A distiller friend of mine here in Germany gave me some lye to clean my kegs with and it worked great. It cleaned much better than my previous routine, which is telling since I used quite a diluted solution, 50 grams for 20L, recommended is 350 grams for 20L. For each keg, I pumped the lye solution through at 80C, emptied, then pumped 95C water through for one minute as a rinse.
Is my rinse long enough?
Is it necessary to passivate the kegs after this? (I also read up on the possibility of corrosion, but from what I have gathered that can really only occur at concentrations higher than what I am using.)
Thanks for the help!
Without having a better knowledge of what your "lye" contains in chemicals, and without perhaps knowing what you were using before, a definitive answer is not possible. However, assuming it is sodium hydroxide, or less likely, potassium hydroxide, plus various additives to help the hydroxide to work more effectively and prevent scale build up, then no, you don't need to passivate.
If you are using potassium hydroxide based material, then my understanding is that this is far more expensive than sodium hydroxide based material, and you are highly likely to be wasting money and should switch to a sodium hydroxide based equivalent. I have only ever used KOH for degreasing new equipment, but now simply use stronger NaOH at higher concentrations and higher temperature than for normal CIP - and it seems to work well.
You should never need to passivate, apart possibly when you first get new equipment. Degrease, give a normal clean, passivate then give a normal clean before use for brewing. Kegs, with the exception of some Chinese kegs I have seen don't normally need passivation as the steel quality is good, and, if from US or European suppliers, will probably have been degreased then passivated by the manufacturer.
NaOH does not strip the protective layer of chromium dioxide from the stainless (which is what makes it stainless).