Being as your going to strip and powder coat them anyways, get some muriatic acid (pool acid) and a plastic bucket and put about a gallon of water to a gallon of acid (important to add the water to the bucket THEN the acid.) and soak the nozzle/bucket for about an hour.
This will free the scale from around the stainless pin and it should literally damn near fall out...Just be sure to rinse the parts in plenty of fresh water before you grab hold of it..

Been doing this for 20 years and this is by far the least destructive and least amount of labor this could be done....

It may require a second dunking...If really stubborn, a third....

GT