Looks like either carbon spots or slag in the alloy. If it's slag you can't remove it, if it's carbon spots, only a quick dip on ezest will work but it's not a guarantee.
You can try soaking it in acetone for a day or two or seven first, and should, but I don't think it will have any appreciable effect. But try it first
Edited by Cascade
05/01/2016 11:17 am