Agreed with Hardgain81. Stick with the compound expercises.
I've had a hard time as well putting on size to my arms. I think it's because they are a small muscle and I use to over train them alot (thinking that would help) However the last 2 months I put on 1/4" to each arm, just by doing compound exercises 3 times a week. And arm targets once a week ( only about 12 sets total ).