I have been having issues with interior lights not working and heater etc, I pulled the fuse box off and all the terminals are very corroded. I haven't disconnected the wires from the car as it looks like some run into my main wiring loom and I'm wondering if it is possible to somehow soak the box in some type of chemical to clean the terminals up. The guy before me had put grease on everthing and it is very messy. I have enough slack in the wires to set something in the car to soak it in but I'm wondering if someone has done this before and what they used. The fuse connectors are very rusty but seem to be OK other than that. wires are solidly connected to the back of the box so I can't just disconnect them. I've also had the generator light on but it's charging as my volt meter indicates 12.7 volts and I have a constant drain on the battery of 12 volts I read on the 2 wires that come off the horn relay & starter battery connection. Lots going on here but my main concern now is the fuse box.

Sorry for tany spelling mistakes and thanks for any help.

 

A dremel tool and the appropriate little attachments can help clean those up.
Putting a little dielectric grease on the mating surfaces can help defer any new corrosion.
I would not soak electrical wiring in any kind of rust remover, as it will migrate up the wires into the insulation where it cannot be washed out. After a short time, the remaining acid will corrode the wires to the point they burn open or start a fire.

 

I use contact cleaner and an acid swabbing brush with the bristles cut really short. Then a pocket knife or xcacto knife and scrape the rust off gently.

 

Dielectric grease should not be used on the contact surfaces themselves, it can actually insulate them. CRC makes a spray fast drying contact cleaner that works well and will not affect the plastic box. You still have to find a way to scrap the fuse connector and the methods above will work. Maybe try a small brass "toothbrush".
I just cleaned mine. I actually removed each fuse holder from the block, as discribed in the manual, but if yours are rusty they may break when you try to get them out. Then you are in a bind as I don't know where you could get replacement fuse terminals. It was not easy to get them out and very tedious. (a real PITA)

 

Remove the fusebox and associated wiring/ dash

EVAPORUST - eats rust, is not an acid.

or perhaps a new repro fusebox/ wiring.

Reinstall

Not a small job, but oh the benefits.

In restoring a '66 442 a while back, I took the back off the fuseblock and fond that two of the wires were rubbing each other, almost to the point of contact. Fixed that too.