Zinc anode slab

01

Choose the zinc grade and the specification for the use

ASTM B6 covers zinc metal produced from ore or other material by distillation or electrolysis in five grades — LME grade, special high grade, high grade, intermediate grade and prime western grade — each with limits on lead, iron, cadmium, aluminium, copper, tin and total non-zinc metals. The metal must be free of surface corrosion and adhering foreign matter, and samples are taken from the molten metal during casting and may be cast into shapes for spectrochemical analysis. B6 notes that continuous-galvanizing and controlled-lead grades are covered by other specifications or purchaser documents. [1] The reviewed B6-23 scope excludes zinc produced by sweating or remelting secondary zinc; the public summary is not the complete purchased standard. [1]

The reviewed ASTM B418-16a(2021) summary covers cast and wrought galvanic zinc anodes for protecting more noble metals and alloys in seawater, brackish water and other corrosive environments. It says Type I meets the chemical-composition requirements of MIL-A-18001K; that statement concerns composition, not complete qualification to every military-specification requirement. The summary discusses Type II for other waters, electrolytes, backfills and soils where experience has demonstrated efficient, reliable service. [2]

Editorial note: name the specification and grade or type on the order — for example ASTM B6 with a named grade, or ASTM B418 Type I or Type II — because the two specifications control different impurities for different purposes. [1] [2]

Give the supplier the specification and grade or type, maximum lead, iron, cadmium, aluminium, copper and tin, slab dimensions and weight, lug or hook design, core or insert if any, surface condition, sampling and analysis method, certificate, packing and quantity.

02

Set size, lugs, sampling and trade paperwork

The USGS Mineral Commodity Summaries 2025 zinc sheet reproduces tariff nomenclature dated 31 December 2024: unwrought, unalloyed zinc is divided at 99.99% zinc, with 7901.11.0000 for the higher-purity category. This historical trade classification is separate from an anode service specification. It does not determine whether a particular finished anode is classified as unwrought zinc or establish a current duty rate; obtain shipment-specific classification separately. [3]

USGS reports that galvanized steel was the leading use of refined zinc in the United States and that 2020–23 refined zinc imports came from Canada (59%), Mexico (16%), the Republic of Korea (7%), Peru (7%) and others (11%). [3]

Editorial note: slab dimensions, weight and lug design are not set by B6; agree them on a drawing, together with how the sample for the certificate is taken (from the melt, per B6, or from the finished slab). [1]

03

Require separate evidence for plating zinc and galvanic-anode alloy

Match the supplier’s heat analysis and drawing to the named use. A high-purity zinc statement alone does not establish the alloy chemistry required for a galvanic-anode type; the B418 summary identifies intentional alloy constituents as well as limits. For a plating bath, agree the applicable zinc grade and the bath-specific impurity limits. [1] [2]

04

Check zinc anode chemistry and capacity for cathodic protection

Deepwater’s zinc column is labelled MIL-A-18001-K. It lists Al 0.1–0.5%, Cd 0.025–0.07%, Fe ≤0.005%, Cu ≤0.005%, Pb ≤0.006% and other elements ≤0.10% each, with zinc the remainder. The electrochemical table identifies −1.05 V against Ag/AgCl specifically as the open-circuit potential and gives 780 A·h/kg as nominal current capacity. Its zinc closed-circuit potential entry is N/A. These are source-specific values, not a measured certificate for another supplier’s slab. [4]

Editorial calculation: assuming a constant 1 A mean demand for 365 days at 24 hours/day and an applicable nominal capacity of 780 A·h/kg, charge demand is 8,760 A·h and charge-equivalent mass is 8,760 ÷ 780 ≈ 11.2 kg. This ideal calculation does not include a design utilisation factor, connection/current-distribution constraints or a separate self-corrosion/design allowance. It is not manufacturer-published installed mass, measured consumption or a guaranteed service life. Establish the design basis and capacity test conditions before sizing the installed anode. [4]

Name the actual service and the contracted standard/type. B6 describes slab-zinc metal grades; B418 describes galvanic anodes and says Type I meets MIL-A-18001K chemical-composition requirements. The two public summaries do not establish a universal rule that every plating/refining bath must use B6, or that a zinc-purity label qualifies a B418 anode. [1] [2]

05

Tie chemistry, cast shape and connection to the service

06

Record the actual slab and batch analysis beside the bath conditions

07

Send the grade, use and slab data together

Paste it into your enquiry below or into an email to a maker, then replace every bracket.

Use: [electrolytic bath; cathodic protection]
Spec/grade: [ASTM B6 grade; ASTM B418 type]
Impurities: [Pb; Fe; Cd; Al; Cu; Sn]
Slab: [L × W × T; kg; lugs]
Sampling: [melt; slab]
Certificate: [analysis; HTS line]
Quantity: [t; pieces]

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