partly with black oily substance

Basically, the box looks quite passable and China now produces for so umpteenth parts of our everyday -So we have ordered the part. However, after one wash in the dishwasher and closer inspection we noticed that it is partially provided with a black oily substance. Seems to be a production residue. Have the can with vinegar .... cleaned and again washed in the dishwasher - is now clean. Time approx 0.5 hrs.
For this effort, I can not forgive only one star :-(.