360 undertray bolts - special coating, or hardware store grade?

I lost on of the bolts holding the undertray on. Since it screws into the aluminum frame, do you have to worry about galvanic corrosion, or am I screwing into an coated steel insert?

Thanks!
David

 

I just took mine off last night, to loosen the lower rear A-arms to readjust the camber shims that worked themselves loose. There are 4 screws on the rear cone, and 4 on the rear of the tunnel. There are more of the the bolt type though, that's used everywhere else. They are the ones that bolt into the inserts embedded into the frame, and that's what I've lost. BTW, I got one of those blue Bosch electric lithium srewdriver guns from Lowes, and it works great for removing all the bolts/screws that attach the undertray.