Note before reading: I am not blaming the manufacturer of the product for this. There was nothing wrong with the product as far as I can tell. Just 3+ years of 24/7 use. I even replaced the block with another from EK.
Just thought I would throw this image out for your viewing pleasure. I pulled my 390x out of service because the waterblock started doing this:
It began with edges in the raised area of the block that butt up with the plexi cover. It worked its way across the surface, but not the main flow channels of the block.
Two months back, I pulled my system apart and cleaned everything out. This removed the tarnish that built up on the copper and also on the cooling fins. The video card was oriented with the vid cables on top (90deg board rotation case). So, the worn fins were the lower most fins.
After cleaning with a very mild vinegar solution (about 1 cap to 1/2 gallon of water), soap with hot water and a toothbrush, then flushed with hot water, then distilled, everything was put back together. Over the next month or two, the copper seems to have oxidized rather oddly. I would have expected it to turn green, but I'm not a metallurgist, so I know nothing. instead it seems to have shed copper into the distilled water.
My best guesses: there was no corrosion inhibitor in the distilled water. Perhaps some corrosion built up, shed off other parts like the rads and worked its way into the gpu block. Then corrosion and scratching from those flakes wore away the nickel plating. On a closer look, there is significant thinning in the nickel near the fins along the exit path through the block.
I just find it extremely odd that the primary nickel loss is between the block and plexi cover. There shouldnt be water flow through these areas, but clearly there is. I'm guessing the initial wear widened the path and made it a high pressure flow path which accelerated the process. 5 months ago, there was no noticeable copper areas.
Result was I pulled the card and block, replacing with a 5700xt and new EK block. (added corrosion inhibitor as well) I was worried that copper was leaching into the water and may cause similar wear on other blocks and pump. There was a very slight copper color to the water after 2 months, but that may have been the old tubing and brownish color of the lighting.
So...anyone else have a block do that?
Edit: I probably should also note that I had the water flowing through the jet plate in the wrong direction for 3 years and didn't notice.