Clogged Radiator

[L DC]

Hi all!!
 
I'll say the the radiator in one of my QSWs is about 30-40% clogged. Once 1st radiator fan speed comes on, it stays on, with the high speed cycling on and off.
 
It is an all-metal radiator and I took it to a radiator shop about 2 years ago where the top tank was taken off to clean it. The did a half-ass job to say the least.
 
Anyway, before biting the bullet to buy a new one at the cheapest place I could find it at a cost of $274 (AutohausAZ.com), I would like to know if any of you know of some chemical I can pour in it to loosen up all the deposits within it. This I would do out with the radiator removed from the car, which I already have.
 
Thanks in advance and regards,
 
-Louis