Thought this warranted a advisory. Last year I tested the Evapo-Rust Gel on the interior of bowl. There was missing porcelain where the leg sockets were welded and it was badly rusted. I usually use #0000 steel wool but thought it was worth a try. As careful as I was to only apply to the rusted, bare metal areas, a small amount of Gel got onto the porcelain. After 30 minutes I washed off the Gel and found it had etched or discolored the porcelain around the bare metal areas. Thankfully, it was a very small area and is not really noticeable as this is a "user" kettle.
Unfortunately for this fella, he wasn't so lucky as to "not really noticeable". He posted this photo yesterday on FB Weber GrillGiants.
Sad part was he posted a question about removing rust on the same site about 5 hours earlier. Someone recommended he use Evapo-Rust Gel on that thread. Sadly, I didn't see either post until after the damage had been done. I maybe could have prevented him from damaging his kettle had I been able to advise him of possible porcelain damage. Hence this post, hopefully preventing anyone from using Evapo-Rust Gel on porcelain.