On Sat, 22 Jun 2019 01:16:21 -0700 (PDT)
Lee Nowell wrote:

Hi all

In a previous post about getting rid of rust, some of you suggested
phosphoric acid. Finally getting around to sorting out my BBQ and
looking on eBay seems like there is a wide variety of strengths
available from 30% to 85%. Anyone know what impact the strength has?
Eg does it work quicker / impregnate deeper / etch the metal etc.
Trying to work out what strength to get.

Also are there any advantages in getting a branded rust eater
instead?

I've used acid-based rust remover (phosphoric and hydrochloric) with
variable results in various applications. Then after seeing many
recommendations online I bought some EvapoRust; bloody marvellous stuff
- no risk of dissolving what you're trying to clean, no worry about
splashing acid where you don't want it, no attached residue of converted
rust, just a black powdery precipitate that rinses away to reveal shiny
steel.
For a BBQ I'd probably just attack it with a wire brush on a grinder,
then apply a coat of oil every so often to keep the rust away.