Every shipment of Atso Tek zinc dust ships with a Certificate of Analysis (CoA) referenced to ISO 3549 (chemistry) and ISO 787/10 (specific gravity). Buyers who only check the line that says "99% zinc" are leaving real risk on the table. Here is what each line on the CoA actually tells you.
The chemistry block
Total Zinc. Total elemental zinc, oxidized + metallic. Catalogue typical: ≥ 99.0%.
Metallic Zinc. The active fraction that protects steel. Typical: ≥ 96.0%. The gap between Total and Metallic is mostly ZnO from surface oxidation.
Pb / Cd. Heavy metal limits. Typical max: 0.05%. Critical for REACH-relevant downstream sales.
Fe. Iron contamination. Typical max: 0.001%. Higher iron means a less pure feed-stock.
As / Cl. Arsenic and chloride trace. Typical max 0.0001% / 0.001%.
Particle size (d0.5). Median by laser diffraction. Verify against the grade you ordered (Superfine 2 to 4 µm, Fine 4 to 5 µm, Fine Flake 4 to 6 µm).
Sieve residue. What is left on a 32, 45 or 90 µm screen. Higher numbers mean coarser tail.
Color. Should read "Bluish gray". A dull or yellow tint usually means oxidation in storage.
Shape. Spherical or Flake, verified by SEM. This must match your application.
Specific gravity. 7.0 to 7.2 per ISO 787/10.
We issue a fresh CoA per lot, not per shipment. If you receive a single CoA covering multiple lots, ask your supplier to break it out. Lot traceability is a lot more useful when you are debugging a batch issue six months later.
