Step-by-step explanation:
The main difference between surface erosion and bulk degradation is that in surface erosion as the name implies that the material or polymer begins to erode or degrade only from the external surface until it reaches the interior of the material. However, in bulk degradation, the material undergoes complete degradation from within and outside the material.
Surface erosion is best applied in pharmaceuticals in terms of drug delivery into the body, while bulk degradation is best applied in plastics which may degrade in any form.