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Electropolishing product problems

Hi, I'm Ari from indonesia. I work for company who do electropolishing for stainless steel outdoor furniture. It has been three years we running the ep, but recently we get this problem (please see attached photo).

The ep solution ingredients are sulfuric acid 98 % , 75 % phosphoric acid (3:7) and adding some cromium.During this three years we tapped off the top of the solution and adding new fresh solution one time per year (20 % of total volume).
temperature of the bath 50 C. we put ss frame table with 7 voltage & 2500 ampere. The surface of the ss frame is shinny but only one surface area goes like this picture (normally in the bottom) .it looks like chemical solution left in the surface. I try to clean it but still doesn't work. what's the problem in my ep products? where can I take the ep solution to be check for laboratory test?
please help.....

Ari Pratami
plating shop employee - Surabaya, Indonesia
October 16, 2010