Durability is a broad term. It can include things things like environmental exposure, chemical resistance, mechnical wear, impact resistance, etc. Often, a coating is good in one parameter but poor on another. For instance, paint stands up well to general enivironmental exposure, such as being left out in the rain, but does not stand up well to impacts, such as chain slap. Chrome on the other hand, stands up very well to the impacts, but does not do nearly as well with environmental exposure. So, when we say chrome is durable, we really have to qualify the durability with a specific type.