Electrochemical Equivalents and Plating Efficiency Reference Table
Every plating calculation starts with the same handful of constants. This reference collects atomic weight, valence, density, electrochemical equivalent and typical efficiency for the metals shops plate, so you can feed them into time, thickness and cost estimates.
| Metal | Typical bath | Atomic weight (g/mol) | Valence (n) | Density (g/cm3) | Electrochemical equivalent (g/Ah at 100%) | um per hour per A/dm2 at 100% | Typical cathode efficiency |
|---|---|---|---|---|---|---|---|
Copper | Acid sulfate | 63.55 | 2 | 8.96 | 1.1856 | 13.232 | 95 to 100% |
Copper | Alkaline cyanide (strike) | 63.55 | 1 | 8.96 | 2.3712 | 26.4641 | 30 to 60% |
Nickel | Watts / sulfamate | 58.69 | 2 | 8.9 | 1.0949 | 12.3025 | 93 to 98% |
Zinc | Acid chloride | 65.38 | 2 | 7.14 | 1.2197 | 17.0831 | 92 to 98% |
Zinc | Alkaline non-cyanide | 65.38 | 2 | 7.14 | 1.2197 | 17.0831 | 50 to 80% |
Zinc | Cyanide | 65.38 | 2 | 7.14 | 1.2197 | 17.0831 | 60 to 90% |
Cadmium | Cyanide | 112.41 | 2 | 8.65 | 2.0971 | 24.2442 | 85 to 95% |
Tin | Acid sulfate | 118.71 | 2 | 7.31 | 2.2147 | 30.2963 | 90 to 100% |
Chromium | Hexavalent hard chrome | 52 | 6 | 7.19 | 0.3234 | 4.4975 | 10 to 15% |
Silver | Cyanide | 107.87 | 1 | 10.49 | 4.0248 | 38.3684 | 95 to 100% |
Gold | Cyanide (acid or neutral also used) | 196.97 | 1 | 19.32 | 7.3494 | 38.0401 | 30 to 90%, varies widely |
Iron | Ferrous chloride / sulfate | 55.85 | 2 | 7.87 | 1.0419 | 13.2394 | 90 to 98% |
Lead | Fluoborate | 207.2 | 2 | 11.34 | 3.8655 | 34.0875 | 95 to 100% |
Palladium | Ammoniacal / chloride | 106.42 | 2 | 12.02 | 1.9854 | 16.5173 | 90 to 100% |
Rhodium | Sulfate / phosphate | 102.91 | 3 | 12.41 | 1.2799 | 10.3137 | 30 to 70% |
Platinum | Phosphate / sulfate | 195.08 | 4 | 21.45 | 1.8197 | 8.4835 | 10 to 50% |
Electrochemical equivalent is atomic weight divided by (valence x 26.801 Ah/mol) and the last two numeric columns are computed from the first three. Efficiency ranges are typical literature values for guidance; actual efficiency depends on bath composition, temperature, current density and condition, so use your own measured value. Alloy and electroless deposits are not covered.
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How to use the table
Search for the metal or bath, then read atomic weight, valence and density into the Faraday plating calculator. The electrochemical equivalent column gives grams per ampere-hour at 100 percent efficiency, and the rate column gives micrometers of deposit per hour for each A/dm2, also at 100 percent. Multiply by your current density and measured efficiency to get real deposition rate. Export the table to Excel to use in your own estimating sheets.
- Use valence that matches the bath chemistry, not just the metal
- Multiply by cathode efficiency before using rates
- Check density against your own deposit measurements
- Search by metal or bath name
Where the numbers come from
Atomic weights and densities are standard handbook values for the pure metal. Valence is the number of electrons per deposited atom for the bath type: copper is 2 in acid sulfate but 1 from cuprous cyanide, and chromium is 6 in hexavalent baths. One mole of electrons equals 96,485 coulombs, which is 26.801 ampere-hours. The electrochemical equivalent is atomic weight / (n x 26.801).
Reading efficiency ranges
Efficiency is the fraction of current that deposits metal rather than evolving hydrogen. Acid copper, nickel, tin and acid zinc are close to 100 percent, so Faraday calculations are accurate. Hard chrome sits around 10 to 15 percent, so time estimates must include efficiency or they are off by a factor of seven or more. Alkaline zinc and gold vary with composition and current density, so measure them.
Common mistakes
Frequent errors are using the wrong valence for cyanide copper or gold, applying 100 percent efficiency to chrome, and treating alloys such as zinc-nickel as pure zinc. Deposit density can also be lower than handbook values, particularly for bright or porous deposits. Calibrate against measured thickness on a coupon.
Frequently Asked Questions
What is the electrochemical equivalent of nickel?
For divalent nickel it is 58.69 / (2 x 26.801), or about 1.095 grams per ampere-hour at 100 percent efficiency. At 95 percent efficiency the effective deposit is about 1.04 g per Ah.
Why is the valence of copper different between baths?
Acid copper sulfate contains Cu(II), which takes two electrons per atom, while copper cyanide baths deposit from Cu(I) with one electron per atom. The same current deposits twice as much copper from the acid bath, ignoring efficiency.
What is the Faraday constant in ampere-hours?
One Faraday is 96,485 coulombs per mole of electrons, equal to 26.801 ampere-hours. It is the number used to convert between current and moles of metal deposited.
Are the efficiency numbers guaranteed?
No. They are typical ranges. Real efficiency depends on bath composition, temperature, current density, agitation and bath age. Measure it with a coulometer or by weighing a test panel for production calculations.
If you maintain process data for plating baths in spreadsheets or an ERP, we can help build a private assistant that returns the right constants and estimates directly from your routings.
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