The ONLY way to protect "coilovers" as you call them is with a corrosion resistant spray WAX.
The fact you are asking this question means that you obviously do not have a lot of experience with "race" suspension on the road. ACF will only get you so far, and require constant re-application. Road salt, dirt, and water are mortal enemies of finely adjustable alloy shocks, and you will find without CONSTANT TLC your lovely new suspension will age faster than a Liverpudlian prostitute addicted to crack.
My experience on the matter is that I would spray the life out of them with a proper wax, which can withstand the abuse they get on the road in all weathers. This will not look as pretty, but if you have just dropped £2-£3k on suspension and insist on running it on the road, its a must IMO. ACF50 is "ok", but you need something more robust than simply an oily microfilm.