I have used both evaporust and metal rescue and they have their benefits. Normally left them in for 24hrs heavier rust needed 2 or more treatments. The stuff is too expensive and loses its effectiveness, electrolysis is another good option and suited for heavier rust.
Edd China did a video once were he submerged a land rover chassis into evaporust mostly likely a sponsored video since the cost of the liquid would make you go bankrupt.
