The second exercise that i would suggest for strong arms is Shadow Boxing.

Stand erect with both the legs placed apart.
Position your arms in the boxing pose as shown.
Stretch your fist imagining that you are thumping somebody. Now as you take your hand back visualizing that you are saving yourself from the opponent blow curving your knees.
Now for the next blow instantly move your fist imagining punching somebody under the jowl.
Repeat the punches till you get exhausted.