1 pipe steam radiator sludge

NotSoYeung

hi guys, 

I'm new here, but been a service technician for a few years, got more things to learn.

I have a 11 radiator 1 pipe steam boiler system, I have been incrementally improving upon it, mostly from information here.  Below is what I have installed.

anyway, my current problem is dealing with banging noises.  it's almost like a drum roll banging noises at a few radiators.

Recently, upon removing 3 radiators, ( install flooring under the radiator), I see a large buildup of scale (it feels as solid as the cast iron) inside one radiator.  Presumably this can cause a pocket of water and cause hammering.  is there any chemical I can use to soften this scale/sludge for easier removal?