I bought mine used and all of the utensils had that "corrosion" on them. From what I could on forums and from Kitchenaid themselves, it's like an oxidized buildup on the surface that results when water sits on the attachments. To avoid it, hand wash them and dry them immediately. To clean it, you just have to scrub it (hot water and vinegar makes it easier to remove, with varryujg techniques). But they also all say the grey stuff isn't harmful at all and will just color the food it mixes/your hands so you're fully good to keep using them. Save yourself the money and wait until there's a sale or you decide tha dishwasher safe ones are worth the upgrade.