Irregular holes, voids, or imperfections in the surface of metal usually caused by either casting imperfections (e.g., gas formation during casting), the washing away of inclusions of soluble materials or by corrosion. Generally, pits are small; they may be localised (concentrated in select areas) or may be found throughout the sculpture or metal substrate. See example images below:
Pits caused by corrosion in zinc.
Pits caused by corrosion in bronze.
Pits caused by corrosion in wrought iron.
Pits NOT caused by corrosion but by gas formation during casting. These holes or this texture is often referred to as 'gas porosity'.