I too use these, of a nefarious origin, means I don't remember. Wear safety glasses or better, goggles - pieces of wire can detach. Worse if you take the guard of the angle grinder.
Take care, stay safe
Jonathan
Angle grinders are lethal and should be treated with considerable respect. I will not say the scare me but the opportunity for an accident is immense. I find that if you wear decent protective gloves the switch is very difficult operate, switching on - off is easier (taking note of Alfie's comment).
A safer option than a stainless brush are lap wheels (?) where the item is made up of overlapping abrasive segments or the impregnated wheels used to remove paint. Both of these options have been mentioned in previous posts. I'd say both of these options have quicker wear than the stainless brush - so if the item is large you will need spares. The wire brush is much quicker but you sacrifice some safety.
Another option for cleaning rust, I might have missed it in previous posts, is to apply heat. I think iron oxide has a different thermal expansion than steel and if you get the item hot the bond between steel and rust is reduced and its easier to clean (scaling?)
If the item is large, like a steel yacht - consider having it processed by a professional company with a grit blaster.
Jonathan
My experience of using Evapo-rust on some old rusty tools was very disappointing.Evapo-Rust is good, but expensive, stuff to actually remove rather than convert the rust but best way is to actually dip the item in it rather than just paint it on
This; pretty much every proprietary rust treatment will ask you to abrade the surface to remove loose rust, typically with a wire brush. With the amount of area you have I'd use a wire brush in an angle grinder otherwise it will take forever. My current favourite is Vactan but there are many available for not much money.You should physically remove as much rust as you can. Chemical treatment to what's left if you must, but it isn't a magic short cut.