From R&A rules Q&A about woods, not sure about wedge:
Q.The face of my driver has developed a crack through the normal course of play. I want to carry on using the club, but does it conform?
A. If the crack is a hairline crack which cannot easily be detected by touch, then it would be regarded as wear rather than damage and, as such, the driver could continue to be used. As soon as the crack becomes more than a hairline crack (e.g. it develops a sharp raised edge, or there is essentially of a hole in the face), it should be regarded as a damaged club which is non-conforming.