JoyZhong

Hi just want to ask, I've bought Nd ingot also ,but they come in small pieces (5mm-10mm) and was previously immerse in certain kind of mineral oil. so there's a dark surface on the metal, is there any chemical that can wash away this dark surface without hurting Nd metal itself too severely? I've thought about diluted HNO3, but just afraid the Nd will react with it and won't left me anything behind, cause my Nd ingots are quite small.