Rivnuts?
 

This may sound daff! is it steel ones for steel and ali for ali?
cheers

Agreed. I've used ally ones and already I had 2-3 bolts stuck with the rivnut turning in its place.

ok cheers for that

There a compound you can put in to stop the reaction between metals, we use to use it putting steel helicoils in to ali tank hulls. Can't remember what its called though!

Squirt of WD40 into box section would not hurt either .

do people use ali because they are easier to form then?
tony

Probably because they're cheaper. It is how to build a car on a budget ;)

The ali ones are sh!t though. They're quite soft and it's very easy to damage the threads in them.
I'd only use stainless if I was starting again, or even better use weld-in inserts instead.

Steel rivnuts over m6 are almost impossible to form with a hydraulic tool.

To limit galvanic corrosion you can use something like duralac, but its designed to go between plates rather than on a threaded insert, not sure how well it would withstand rotation whilst its drying.

I used steel zinc plated rivnuts to fit the bodywork. I put a bit of Sikaflex around all of them before crimping. So they also are a bit bounded too and not only crimped (which will make them even more difficult to get loose) and I believe it makes a protection layer/sealing. The excess is easy to clean with alcohol afterwards. It cheap too.

2014-07-08_10-28-13 by Voucht71, on Flickr

Mastinox it's called. We use it in work on Eurofighters

http://www.silmid.com/products/masti...-27-mil-p.aspx