What is electroplating?
The deposition of a metal layer onto a part by electric current. This page answers what it is, where it differs from hot-dip galvanizing, what the real risks are and how the price is built.
Electroplating is the name of the family; electrodeposition is the name of what happens. The part goes into a bath as the cathode, the metal of the layer comes dissolved in that bath, and the electric current deposits it on the surface. What comes out the other side is not a "part painted silver": it is a coating with a specified thickness, a defined alloy and a measured result.
That measurement is what separates the category from a cosmetic finish. An electroplated part can be checked afterwards: thickness in micrometers, alloy composition in percent, corrosion resistance in test hours. The customer who specifies does not buy the bath — they buy the number it produces.
Hot-dip galvanizing is not electroplating.
They are two different processes with similar names, and whoever orders one and receives the other finds out at assembly.
Hot-dip galvanizing
A thick layer, tens of micrometers, that follows the shape of the part and varies with it. It suits exposed structure, where a mass of zinc is what you want and tolerance is not the issue. It is not what Sapucaia does.
Electroplating
Current deposits the layer, and the thickness is specified, applied and measured. It is what lets you meet a standard class, keep the thread within tolerance and combine a metal with an organic finish on top.
Five steps, and what each one decides.
Surface preparation
Degreasing, pickling and activation. The layer does not adhere to a dirty surface or to oxide: what fails in the field almost always failed here. When the part needs an anchor profile, blasting comes in; when it needs a conversion base, phosphate comes in.
The bath, and the current
The part becomes the cathode. The bath composition and the current density determine the alloy deposited — in zinc-nickel, the 12 to 16% nickel range is what the standard sets and what the laboratory checks, lot by lot, in bath analysis.
Passivation or finish
On the pure metallic layer goes the conversion coat, which is what the standard designation calls the type. Where the system carries an organic finish — PTFE Sapucaia or Xylan® —, the top is different, and the function changes: a chemical barrier to the medium and predictable friction in the joint.
Thermal relief, when the material needs it
High-strength steel goes to the oven to release the hydrogen absorbed in the bath. It is a recorded step, not an optional finish — and the standard and class come from the customer’s specification.
Measurement, and what it proves
Thickness and alloy composition by X-ray fluorescence, with traceable standards calibrated by an ISO/IEC 17025 accredited laboratory. It is what turns "it was zinc plated" into a number your end customer can check.
Which coating, then.
"Electroplating" is the category. What goes on the drawing is the designation — and each one has its own standard, class and thickness, with the test result and the source of the data on the process page.
Alkaline zinc
ASTM B633 and ISO 2081. It covers what indoor environments and light industrial atmospheres ask for, at a fraction of the cost of an alloy.
Zinc-nickel
An alloy with 12 to 16% nickel, under ASTM B841 — in the class, type and grade the order determines.
NanoGalv®
Nanostructured zinc-nickel to ASTM B1025-25, exclusive licence in Brazil. It is the layer that changes the order of magnitude.
Process index
Cadmium, phosphate, blasting, hydrogen embrittlement relief and the fluoropolymer finishes, each with its data sheet.
The incomplete designation.
Ordering "zinc plated" — with no class, no type and no standard edition — hands the decision to whoever applies it. On the finished part the result looks the same; in the field, it is not. Alkaline zinc with black passivation and black zinc-nickel have the same color finish and differ by nearly an order of magnitude in resistance.
And the standard edition is part of the specification: subsea equipment bolts failed in the field because the applicator followed an old edition of ASTM B633, which did not yet require the hydrogen relief the next edition began to require. The supplier was legitimate, certified and audited.
The math is public.
Electroplating is charged by processed load, not per part. What goes into the calculation is the weight or area of the part, how much fits in one bath cycle, the coating specified and the thickness required. The load equation and the constants by material are published — showing the math is worth more than saying it exists.
What people usually ask.
What is electroplating?
Electroplating is the deposition of a metal layer onto a part by means of electric current, inside an electrolytic bath. The part goes in as the cathode, the metal of the layer comes dissolved in the bath, and the current deposits it atom by atom on the surface. The technical name of what happens is electrodeposition. Thickness is controlled in micrometers and measured afterwards — at Sapucaia, by X-ray fluorescence.
What is the difference between galvanizing and electroplating?
Hot-dip galvanizing dips the part in molten zinc, with no electric current: the layer comes out thick, tens of micrometers, and the thickness varies with the shape of the part. Electroplating deposits by current, so the layer is thin, uniform and specifiable — which matters when the part has a thread, an assembly tolerance or a standard that fixes the class. Sapucaia does electrodeposition, not hot-dip galvanizing.
What are the risks of electroplating?
Three, and all have a known treatment. The first is hydrogen embrittlement: high-strength steel absorbs hydrogen in the bath and can crack later, once assembled — which is why thermal relief is a mandatory step, to the standard and class the specification determines. The second is a layer out of tolerance: thickness above plan jams threads and changes the fit. The third is the incomplete designation — ordering "zinc plated" with no class, no type and no standard edition leaves the decision to whoever applies it, and that is how subsea equipment bolts failed in the field.
How much does electroplating cost?
The price is per processed load, not per part. It comes from the weight or area of the part, the quantity that fits in one bath cycle, the coating specified and the thickness required. The load equation and the constants by material are published on the How we operate page — the math can be checked. To quote, our sales team needs the part’s technical drawing and the coating standard: with both it returns system, class and thickness, and not just a number.