Electroplating charge can estimate deposited metal mass and an equivalent average coating thickness, provided the reaction, current efficiency, density and plated area are defined. That calculation helps explain how the process inputs affect the estimate. It cannot tell you the minimum thickness at a gland’s thread root, the continuity of a recessed coating or the finished assembly’s corrosion performance.
The useful sequence is charge, deposited mass, then volume divided by area. Once you understand those steps, a calculated average and a local measurement become complementary quantities instead of competing answers.
Define the reaction and the surface receiving the deposit
Start with the metal being deposited and the electrochemical reaction. For nickel deposited from nickel(II) ions, two electrons are involved per nickel atom. Pine Research’s nickel electrodeposition experiment sets out that reaction, the Faraday-law mass relationship and the effect of competing reactions on efficiency.
The electrical boundary also needs a clear definition. Current supplied to a rack of several parts is not automatically current delivered to one gland. Exposed conductive fixtures or other components may receive deposit too. A mass calculation for the entire connected load needs the corresponding plated area; a one-part calculation needs a justified allocation of charge to that part.
Plated area means the actual exposed surface included in the model. It is not the silhouette of the part in a photograph or the area of its bounding rectangle. Threads, shoulders, bores and recesses contribute surface area when they are exposed to deposition. Masked areas and contact locations need explicit treatment.
For a complex gland, I would use the controlled geometry and plating arrangement to establish an area estimate, then record its uncertainty. An undocumented area can dominate the thickness error even when current and time are recorded accurately.
Convert current and time into charge
For constant current in amperes over time in seconds:
The charge is in coulombs. Thirty minutes is 1,800 seconds, so a constant 2 A gives 3,600 C. If the record is in ampere-hours, multiply by 3,600 to obtain coulombs.
For changing current, use the integrated charge:
I prefer the appropriate charge record over a nominal power-supply setting when the current ramps, pauses or changes with the load. A stated average current is useful only if it represents the relevant interval and electrical boundary. Current is not voltage: multiplying a voltage setting by time does not give deposition charge.
Pulse-reverse or mixed-reaction processes need their own treatment of deposition and dissolution. A simple positive-current model should not be extended to them by adding all current magnitudes together.
Calculate deposited mass using a justified efficiency
For the simple single-metal cathodic model:
Here is deposited mass in grams, is the metal’s molar mass in g/mol, is electrons per deposited atom, and is current efficiency as a fraction. The NIST CODATA constants table gives the Faraday constant as approximately 96,485.33212 C/mol.
In this model, efficiency represents the portion of charge that produces the intended metal deposit. Other cathodic reactions can consume charge. Use a value supported for the specified bath, operating conditions and load; a handbook example or an efficient power supply does not establish the deposition efficiency.
For our hypothetical nickel calculation, take:
| Input | Example value | Basis |
|---|---|---|
| Charge delivered to the modeled work | 3,600 C | 2 A for 30 min |
| Molar mass | 58.69 g/mol | Rounded nickel input |
| Electron number | 2 | Nickel(II) reduction |
| Current efficiency | 95% | Assumed process input for this example |
| Deposit density | 8.90 g/cm³ | Assumed density for this calculation |
| Exposed plated area | 100 cm² | Assumed modeled area |
The calculated deposited mass is about 1.040 g. The 95% value is a declared example assumption, not a claim about any Bepto production bath. Where efficiency changes during the run, it must represent the charge-weighted yield or the process should be evaluated by suitable time intervals.
A measured before-and-after mass can help check an overall deposition estimate when the measurement method controls other mass changes. It still cannot locate a thin patch. Cleaning losses, retained liquid or unaccounted deposits make an uncontrolled weight difference misleading.
Convert deposited mass into an average thickness
With density in g/cm³ and exposed area in cm², the equivalent average thickness in micrometres is:
The factor converts centimetres to micrometres. For the stated example, 1.040 g divided by 8.90 g/cm³ and 100 cm² gives about 11.69 µm. This is the deposited volume spread uniformly over the modeled surface area, using a thin-coating approximation.
We can check the result by reading it alongside its inputs. Doubling the area while holding deposited mass and density fixed halves the calculated average. Using efficiency as 95 instead of 0.95 in a handwritten formula would multiply the result by 100; the calculator’s efficiency field expects percent. Check the field units instead of copying the formula’s fractional value into that field.
The calculation does not assign material to individual surfaces. A larger average can coexist with an inadequately covered recess. Nor does the result establish coating composition, porosity, adhesion or any specified minimum.
Distinguish coverage from thickness distribution
Covering power concerns whether the plating system can cover the surface; throwing power concerns how evenly deposit is distributed across differently situated surfaces. The distinction is explained in the Bureau of Standards’ original study, Throwing Power in Chromium Plating, especially its definitions and covering-power discussion. That study’s numerical chromium-bath results are not nickel process settings.
On a gland, an exposed edge and a recessed thread surface occupy different positions in the electrical and solution-flow geometry. Racking, anode position, shielding and surface access can therefore matter. First ask whether a difficult surface receives continuous deposit, and then whether its local thickness meets the specified requirement. Those are different questions.
Consider a separate hypothetical example: two equal-area patches have thicknesses of 2 µm and 10 µm. Their area-weighted mean is 6 µm. A uniform 6 µm layer over both patches would have the same deposited volume, yet a very different minimum. This is arithmetic, not a measured gland coating profile.
Match local measurements to the finished surfaces
Identify the significant surfaces on the drawing before selecting measurement locations: accessible flats, shoulders, sealing seats and relevant thread regions. A reading on an easy flat should remain labeled as that flat’s result.
ISO 3497’s published scope explains that X-ray methods fundamentally determine coating mass per area; density allows conversion to linear thickness. On a small curved gland, the measurement setup must also accommodate the selected location, spot and coating system. A local reading does not automatically describe the full part.
A prepared cross-section can examine a selected layer at its cut location, while a surface method may sample another area. Compare results only after checking those locations and method assumptions. ISO 2177:2003 describes coulometric thickness measurement by controlled anodic dissolution of conductive coatings. That is a measurement procedure, distinct from estimating production deposition using the plating-current log.
The local plating-thickness and corrosion guide develops measurement and acceptance in more detail. Keep adhesion, coverage, local thickness and corrosion exposure as separate results. Also check finished threads and sealing faces against their functional dimensions after coating; an arithmetic thickness estimate cannot approve fit or service life.
Conclusion
Charge and current efficiency estimate how much metal the modeled work receives; dividing its volume by the defined plated area gives the average thickness. The example’s 11.69 µm is useful only with its stated reaction, efficiency, area and density. Changing any of those inputs changes what the number means.
For a finished cable gland, carry that process estimate forward to a location-based measurement plan. Coverage and thickness distribution explain why a plausible average can coexist with a thin or uncovered region, and why local evidence remains necessary when a drawing specifies a minimum.
FAQ
Does twice the plating time always give twice the thickness?
The simple model predicts twice the average if current, current efficiency, density and plated area remain unchanged. Actual process conditions may change during the run, and local distribution can differ across the part. I would use the charge record and relevant process evidence before extending that proportionality to a specific gland surface.
Can I use the total rack current for one gland?
Only with a justified allocation of that charge to the gland. Other parts and exposed conductive fixtures may also receive current and deposit. Keep the electrical boundary aligned with the area used in the calculation. Total rack charge divided by one gland’s area would usually describe the wrong physical model.
What is the difference between covering power and throwing power?
Covering power addresses the ability to deposit across the surface, including difficult regions. Throwing power addresses the distribution of deposit thickness across differently situated regions. A surface can be covered yet thinner than required. I assess coverage and local thickness separately rather than treat either term as a general coating-quality score.
Does a calculated average establish the minimum plating thickness?
No. The same deposited volume can be distributed evenly or concentrated in some areas while others remain thin. An equivalent average has no location information. Use a suitable measurement plan for the significant surfaces and compare its local results with the drawing or coating specification’s stated acceptance criteria.
Sources and technical references
- Pine Research — Exploring Faraday’s Law Using Inexpensive Screen-Printed Electrodes, accessed 2026-10-22.
- NIST — 2022 CODATA fundamental physical constants, complete listing, accessed 2026-10-22.
- Bureau of Standards — Throwing Power in Chromium Plating, RP131, accessed 2026-10-22.
- SIS — SS-EN ISO 3497: X-ray spectrometric coating-thickness methods, accessed 2026-10-22.
- SIS — SS-EN ISO 2177:2004 (ISO 2177:2003): Coulometric coating-thickness measurement by anodic dissolution, accessed 2026-10-23.