Gonna have to use needle scaler to get some of the rust off the 4x6 frame angle iron before I wire wheel and paint, then boards go on. Wire wheeling is a nasty job.
DeWalt wire wheels and used flap disks will take that rust and scale and crud off far better than a needle gun in most instances.
The DeWalt wire wheels seem to last a good long bit compared to the others I've used. Another alternative is just open air sandblasting.
