I use Eastwood Road Salt Neutralizer and a garden sprayer. Spray the entire undercarriage and suspension with the solution, let it sit for a few minutes, then pressure wash it off. Makes a huge difference if you drive your car in the winter w/salt. Also, late in the fall, ususally as I'm swithching to my winter tires, I'll clean the undercarriage really well, let it dry and then apply Boeshield t-9 to all suspension components, steering knuckles, etc. If you get it on your brake discs, take it off with some brake cleaner. Seems to help with the corrosion.