Chris Collins

Tools · fabrication

Anodizing and electroplating calculator

Anodizing and electroplating numbers: current from current density and the part's area, anodizing time by the 720 rule and a Faraday estimate, Type II / III ranges, dye and seal notes; plating mass, thickness and time by Faraday's law for copper, nickel, zinc, tin, silver and gold; surface area from simple shapes or an STL — with the safety notes, and no cyanide.

Added

How to use it

How to use it

Pick metric (µm, A/dm², cm²) or imperial (mil, ASF, in²) at the top; the tool remembers it.

  • Anodizing — choose Type II (sulfuric, decorative and dyeable) or Type III (hard), the coating thickness, the current density and the area. You get the current to set on the supply, the time by the 720 rule — minutes = 720 × thickness in mils ÷ current density in A/ft² (1 mil at 12 ASF is an hour) — and a Faraday estimate from the charge passed: 6 electrons per Al₂O₃, a porous oxide of about 2.4 g/cm³ and a coating efficiency of about 75 % (some oxide dissolves as it grows); with these the two agree within a few per cent. Typical voltages, temperatures and thicknesses for each type, and how to dye and seal, are under the numbers.

  • Electroplating — choose the metal (acid copper, Watts nickel, acid zinc, acid tin, non-cyanide silver, sulfite gold), the thickness and current density; the efficiency starts at a typical value for that bath. You get the current, the time, the mass deposited and the growth rate per hour, by Faraday’s law m = I·t·M ÷ (n·F) × η (F = 96 485 C/mol; M, n and the density for each metal are listed).

  • Surface area — a plate, rod, tube, disc or washer, block or ball from its sizes, or the area of an STL (read in millimetres, in your browser). Use this area sends it to the other two tabs.

  • Safety — read it before you mix anything.

Worked checks the tests use: 2.00 A for 30 min deposits 1.185 g of copper and 1.50 A for 1 h 6.04 g of silver (textbook Faraday examples); Watts nickel at 1 A/dm² for an hour at 95 % grows about 11.7 µm (the shop rule "12 µm per A·h/dm²"); 1 mil at 12 ASF takes 60 min by the 720 rule.

Sources: Faraday’s law and CODATA 2018 for F; IUPAC atomic weights; MIL-A-8625F for the anodizing types (the ranges shown are common practice, not the standard’s limits); the 720 rule as used throughout the anodizing trade (e.g. Caswell’s and Products Finishing’s guides). Bath efficiencies and current-density ranges are typical figures — your supplier’s sheet wins.

Limits

  • All of it is rules of thumb for small, well-agitated tanks at the usual concentration and temperature. Real thickness varies over the part: edges plate thick, recesses thin (throwing power), and anodic coatings are thinner where agitation or contact is poor.

  • The anodizing estimates assume 15–20 % sulfuric acid at about 20 °C (Type II) or near 0 °C (Type III); alloys with copper or silicon (2xxx, cast alloys) anodize slower and darker.

  • Plating mass is the metal deposited; hydrogen takes the rest of the current (1 − η).

  • No cyanide, chromic-acid or hexavalent-chromium processes, by design.

Related: chemistry (Faraday’s law and electrode potentials), parametric parts, speeds and feeds, 2.5D CAM.

Linking to an example

Share link copies a URL with the numbers on every tab; the tab is in the hash (#anodize, #plate, #area, #safety).

Parameter Meaning

units

metric or imperial

type, thick, j, area

Anodizing type II or III; thickness µm; current density A/dm²; area cm²

metal, pth, pj, peff

Plating metal Cu, Ni, Zn, Sn, Ag, Au; thickness µm; current density A/dm²; efficiency %

shape, w, h, t, d, id, L

Area shape plate, rod, tube, disc, box, sphere and its sizes in mm

example

A preset (below)

Presets: Type II, 25 µm at 12 ASF · 10 µm of Watts nickel · area of a rod.

Runs entirely in your browser; nothing you type leaves this page.