I've just began my project and purchase a orbital sander to sand down the surface rust I want to remove
But don't know what grit to use. I don't want something to heavy nor something that I'll be their forever.
Looking for some good advice from those who been their before. Thanks in advance

 

post some pics.depending on how deep or shallow the rust is will dictate the grit you will use,or if you will need to chemically treat it.

 

For an orbital you will probably want something in the 36-50 range. If you can lock it so it just spins I would say try 60-80. Don't be afraid, if it is cancer you want as much of it gone as you can get.

 

Don't use any harsher that 80 grit or it will be hard to get scratch marks out of the steel.