Undersealing the R

Ok, thankyou, so with regards to applying it, can it just be brushed/sprayed lightly on and left to do it's job or do you need to neutralise it after a certain period of time?, also does the area to be treated need to be de-greased first?, sorry for all the questions, but i'd rather have good info from someone that knows what they are doing and has had first hand experience with the stuff, thanks.

Wire brush on an angle grinder is used for removing underseal and loose\heavier rust first then i degrease the whole area with thinners, then using a spray bottle suitable for the acid i spray it all over in a light mist and plenty into the seams to soak them, bad areas usually need spraying again but if their that bad it's usually time to get the angle grinder and welder out....

It dries out itself anyway so I don't neutralise it

Awesome, thanks for the info buddy.  

Nae bother