Electroplating and Anodizing Tank Current and Time

Faraday's law of electrolysis says the mass deposited is exactly proportional to the charge passed, with the constant of proportionality being the metal's equivalent weight over the Faraday constant. Nothing about the bath chemistry, the additives, or the operator changes that -- what they change is CURRENT EFFICIENCY, the fraction of the current that deposits metal rather than evolving hydrogen. Nickel baths run near 95%; decorative chromium baths run in the teens, which is why chrome plating is so slow and so power-hungry, and running the same geometry in a 15% bath drops the deposition rate by more than six times before any other difference is counted. The useful reading is that CURRENT DENSITY, not total current, sets the rate: a part twice as large needs twice the current to plate in the same time, and a rectifier that cannot deliver it simply plates slower -- doubling the rack area without doubling the rectifier halves the current density and doubles the time. Current density also has upper and lower limits set by the bath, too low and coverage is poor, too high and the deposit burns, so the practical rate is bounded by chemistry rather than by the power supply. Nickel at 40 A per sq ft over 20 sq ft of part at 95% efficiency draws 800 A and lays a mil down in about 30 minutes, which matches shop experience closely, because Faraday's law is not an approximation. The sacrificial-anode life calculation here runs the same law in the other direction, on metal being consumed rather than deposited. AVERAGE thickness only, which is the number Faraday's law gives and not the number an inspector measures. Real deposits are not uniform: current concentrates at edges and points and starves in recesses, so a rack that averages a mil may be well over on a corner and well under in a bore, and throwing power, anode placement, robbers, and shields are the whole craft of fixing that. It does not address bath composition, temperature, agitation, filtration, pretreatment and cleaning -- which decide adhesion -- hydrogen embrittlement and the bake that relieves it, rectifier ripple, or waste treatment. Plating baths are hazardous chemistry with serious ventilation, PPE, and disposal requirements. The bath supplier's data, the plating specification, and the applicable environmental and safety regulations govern.

total current = current density x area; mass rate g/s = I x atomic weight / (valence x 96,485) x current efficiency; volume rate = mass rate / density; thickness rate = volume rate / area in cm2; time = target thickness / thickness rate.

Faraday's law of electrolysis, mass rate = current x atomic weight / (valence x 96,485 C/mol) x current efficiency, by name, with deposit thickness following from the metal's density and the part's surface area. AVERAGE thickness only. The bath supplier's data, the plating specification, and the applicable environmental and safety regulations govern.

Faraday's law and the Faraday constant are public physics; the metal's atomic weight, valence, and density are published constants and the current efficiency is entered by the user.

Estimate. AHJ and licensed professional govern.

Field names used by the API: current_density_asf, part_area_sqft, atomic_weight, valence, metal_density_gcc, current_efficiency, target_thickness_in, total_current_a, mass_rate_g_s, volume_rate_cm3_s, area_cm2, plating_time_s, plating_time_min

• Faraday's law is exact mass is exactly proportional to charge; only the current efficiency variesFaraday's law of electrolysis
• Current density sets the rate not total current -- a larger rack on the same rectifier simply plates slowerplating practice
• Average, not local edges run heavy and recesses thin; throwing power and shielding govern uniformityplating practice