YUSHIJIA | Magnetic Wall Mounted Storage Rack Stainless Steel No Drilling Required

Stainless steel 304

I'm about to move into my new house, and before I did, I noticed the knife holder looked dirty (even though no knives had been in it yet). So, I tried cleaning it with a white cleaning paste. The whole thing turned black, and it wasn't just dust. After rinsing the sponge from the cleaning paste, it was still black and wouldn't wash out. When I dried it with a paper towel, it was also black. The black residue that came off when I used the sponge even stained the tiles around the knife holder. Later, I tried dish soap, and it still turned black. The seller's AI chat said it was a normal phenomenon due to some kind of film on the surface. My sink and faucet are brushed stainless steel, and they don't have this issue. Someone told me it's either not 304 stainless steel or the manufacturing process isn't good enough (the passivation process). Now that it's dry, there's a whole black streak in the middle. I don't recommend it.