Nickel powders and flakes under 7504 are metallic nickel in particulate form. Nickel compounds — oxides, sulfates, carbonates, and similar chemical forms — are classified in the chapters covering inorganic chemicals. The distinction rests on whether the material is elemental metal or a chemical compound; a certificate of analysis confirming metallic nickel content is the standard supporting document.

Specifications vary sharply by end use: battery-grade nickel powder typically requires very high purity and controlled particle size distribution, while powder-metallurgy grades prioritize flowability and compressibility. Catalyst-grade material may have specific surface-area requirements. These specifications are set by the buyer's technical standards rather than by the tariff schedule, but they affect which supplier can meet the order and at what price.