Burning refers to a non-adhesive, dark deposition of a galvanically applied layer in which too much current has been applied. The depletion of the cations in the cathode film leads to several reactions.
Burnt-on spots often occur on components at edges and at the point closest to the anode, i.e. always where the highest current density is present. To counteract this, you can either reduce the current (coating time takes longer, if necessary the coating is no longer opaque) or make sure that the metal ions in the cathode film do not become depleted. Possibilities are: