The concern is a surface change without a known leak
Keep the observation separate from a conclusion about perforation or loss of strength. Ask whether the change is in a finish, the underlying metal or material deposited from elsewhere. Product records and a close professional inspection are more useful than a remote color label. A care or coating recommendation should identify the actual material and preparation, not cover an unresolved condition.
Notice next: Photograph the same area in ordinary daylight and locate the product or finish documents, without scraping the surface.