It depends on the product's formulation and function. A metal brightener that operates as a polish or surface preparation — removing tarnish or oxidation through abrasive or mild chemical action — generally falls here. However, passivation treatments, pickling acids, or chemical conversion coatings that alter the metal surface through a chemical reaction are typically classified as chemical preparations under a different heading. The distinction turns on whether the product polishes or chemically transforms the surface.

Beyond customs classification, importers should review the Safety Data Sheet for regulated substances under TSCA, confirm DOT hazard classification if the product contains flammable or corrosive components, and check whether the product's active ingredients appear on any EPA or OSHA regulated substance lists. For food-contact environments, NSF or equivalent certification for the specific metal polish formulation may be required by end-users.