My steel chimney is black at the top and for several inches
down. I think this is because there is often no wind at this location,
thus smoke is free to shed particulates nearby when it hits
colder air, and they are then attracted (electrically) to the
nearest surface. Of course you may have a masonry
chimney -- you did not say.
HomeOwnersHub.com is a website for homeowners and building and maintenance pros. It is not affiliated with any of the manufacturers or service providers discussed here.
All logos and trade names are the property of their respective owners.