Technical overview
ASTM B6 specifies primary zinc in five grades: LME Grade, Special High Grade, High Grade, Intermediate Grade and Prime Western Grade. Continuous-galvanizing grades are covered separately by ASTM B852.
Galvanic zinc anodes are a distinct product. ASTM B418 Type I anodes, which meet MIL-A-18001K, are used for cathodic protection in seawater and brackish water. Type II anodes are used in soils and other electrolytes.
Grades & standards
Grades are distinct materials — properties and uses below apply to the named grade only.
ASTM B6 grades
LME / Special High / High / Intermediate / Prime Western
Composition: Purity and impurity limits per grade — confirm against ASTM B6
- Grade defines lead, iron, cadmium and other impurity limits
Listed specifications: ASTM B6 · ASTM B852 (galvanizing grades)
ASTM B418 Type I / Type II
Galvanic zinc anodes
Composition: Type I meets MIL-A-18001K composition
- Type I: seawater and brackish water
- Type II: soils and other electrolytes
Listed specifications: ASTM B418 · MIL-A-18001K
Forms
Typical industry forms for this material. They are not a stock list — form, size and availability are confirmed per enquiry.
- Ingot / slab
- Anodes (cast or wrought)
- Wire (e.g. for thermal spray — confirm)
- Rod
Applications & industries
- Hot-dip and continuous galvanizing
- Cathodic protection of hulls, piping and structures (anodes)
- Alloy production (brass, die-casting alloys)
- Thermal-spray metallizing (confirm grade)
Selection notes & limitations
- Anode composition is controlled for electrochemical performance; ingot grades are not interchangeable with anode alloys.
What to specify when requesting a quote
- 1ASTM B6 grade or anode type (B418 Type I/II)
- 2Anode shape, weight and insert/strap details (for anodes)
- 3Grade and the standard it must conform to (ASTM, EN, IS, UNS or your drawing)
- 4Form and dimensions — thickness or diameter, width, length and tolerances
- 5Approximate quantity, and whether the requirement is one-off or recurring
- 6Intended application, so the grade can be cross-checked before quoting
- 7Documents required — e.g. mill test certificate, chemical analysis, certificate of conformity
- 8Delivery city / site and the date you need material by
Documents buyers may request
Mill test certificate
e.g. EN 10204 type 3.1 inspection certificate, where the producing mill issues one
Chemical analysis report
heat / lot composition against the specified grade
Certificate of conformity
confirming the material meets the ordered standard
Heat / lot traceability
heat numbers marked on material and documents
Dimensional inspection report
for cut-to-size or machined material
Safety Data Sheet (SDS)
especially for lead, beryllium-, cadmium- or lead-bearing products
Which documents can be provided depends on the source mill and is confirmed with each quotation.
Frequently asked questions
Which zinc anode for seawater?
ASTM B418 Type I anodes, whose composition meets MIL-A-18001K, are most commonly used in seawater and brackish water.
Sources & technical references
- ASTM B6 — Standard Specification for Zinc — ASTM International. Checked 2026-10-14.Full standard is paywalled — only the public abstract and scope on astm.org were read. Composition tables were not accessed.
- ASTM B418 — Standard Specification for Cast and Wrought Galvanic Zinc Anodes — ASTM International. Checked 2026-10-14.Full standard is paywalled — only the public abstract and scope on astm.org were read. Composition tables were not accessed.
