ICD-10-CM > S00-T88 > T20-T25 > T20 > T20.4 > T20.49 T20.49 Corrosion of unspecified degree of multiple sites of head, face, and neck Non-Billable/Non-Specific Codes T20.49XA..., initial encounterT20.49XD..., subsequent encounterT20.49XS..., sequela