I've just refurbished the fuse box for my Firenza. The terminals were seriously corroded after being in storage for many years and unlikely to make a reliable connection when installed.
So I dipped it in a strong solution of citric acid and here is the result.
Nice and shiney and clean. There is no need to dismantle it either as the acid floods the whole box and cleans it thoroughly. This process only took about 5 minutes so is a great service item for a Saturday morning.
I'll also dip the ends of the wiring looms when I get those looked out. There is no need to dismantle them either so it's an easy job too.