stock pot cleaning question

I have a 40 qt stainless steel stock pot. I used some barkeepers friend and a plastic scrub pad to clean it. I let it air dry for awhile, then wiped with a paper towel to completely dry it. The paper towel had a gray color on it. Is this normal? Do I need to clean it again until there is nothing on a paper towel when drying? Also I already did a full boil with it and the beer tastes a little funky.

 

The gray residue is actually an oxide coating formed by the passivation process when using the BKF during cleaning.

It is completely normal, however I make sure to polish all of the gray residue of with a soft cloth after my kettle is completely dry. I also only do a thorough BKF cleansing after avery 5-6 batches.

Now that you have done a full boil since then (I can't say ifthe flavor you describe is green beer, or from a lack of proper polishing) you should not have any issues considering you cleaned your pot after the last use.

Passivation of stainless steel, and aluminim is essential to keep your pots from corrosion and erosion.