Brass - is this corrosion or oxidation and why did it happen?
I have bought a new brass Y-split water valve which is plain brass but inside is a more polished one, it was packed nicely and I opened it 2 days ago, washed it off with water for some reason, then did a bit of drying with a kitchen towel, I then placed it in a plastic container, however it was more of placing it ON a plastic container as I did not seal it or anything.
Today (2 days after, not even 48 hours are passed) I checked it, and on one of the side the brass had these violet/bluish spots (which I thought are reddish/brown spots at first - but at better lightning they are more of a violet/bluish - my photos really do not show their actual colors). So what are they and why did it happen? This valve splitter is used for water so I don't know why this happened if water was the problem.
I tried to scratch it off with paper towels, and then a toothpick - but it did not work. I did not use anything besides water - and it looked perfectly fine 48 hours ago. Similar thing happened to a water aerator - had a perfect new one I actually checked it, put it on the water tap and ran like 3 liters of water and then I wanted to fix something so I got it out and boom it had these brown - reddish spots, but not this dense and this is not that color.
IF this in case is corrosion, my question would be is it possible for the corrosion to happen this fast only from water? Will the corrosion spread and how bad would it be to be used for a washing machine in terms of a health hazard or machine damage (besides leakage)? Again note that the color is not as dramatic as this and the pictures make it looks much more deeper than it is in real life, whereas it looks like there are stains just atop - although they can't be removed. 542