Zinc-nickel plating.
Electrodeposited zinc-nickel alloy, 12 to 16% nickel, to ASTM B841 — class, type and grade as your order specifies. The alloy is measured, not assumed.
Zinc-nickel is the workhorse of offshore bolting. The alloy is sacrificial, like zinc, but the nickel slows the sacrifice down by roughly an order of magnitude — which is why bolting specifications that once accepted plain zinc now call for zinc-nickel by name.
The designation comes from your side, not ours. We deliver the class, the type and the grade your order specifies, within ASTM B841 — including grade 10, the minimum 10 µm that offshore bolting specifications typically require. What we add is the measurement that proves it.
The three things that decide whether it lasts.
The alloy — 12 to 16% nickel
The range ISO 4042:2022 fixes. Outside it the coating either loses corrosion resistance or turns brittle, and neither shows on the finished part. Measured by X-ray fluorescence during the process, lot by lot.
The thickness — and the tolerance it has to live in
Coating thickness is specified, applied and measured. Too little and the class is not met; too much and the thread goes out of tolerance. On a fastener those are equally expensive failures, and only one of them is visible before assembly.
Hydrogen, when the material calls for it
ASTM B849 before, ASTM B850 after, to the standard and class your specification determines. Heat treatment is a step with a record, not an optional finish — high-strength steel that absorbs hydrogen in the bath cracks later, already installed.
Same material, different structure.
When ASTM B841 grade 10 is not enough for the service, the next step is not a thicker coat. It is nanostructured zinc-nickel — the same alloy deposited in alternating nanoscale layers, specified under ASTM B1025-25. We apply it as NanoGalv®, under exclusive licence in Brazil.
The part, the thread and the drawing do not change. Only the line it runs on.
Applied in Guarulhos, São Paulo, Brazil, under ISO 9001:2015. Coating thickness and alloy measured in our own laboratory by X-ray fluorescence, with standards traceable to an ISO/IEC 17025 accredited laboratory. vendas@sapucaia.com
What specifiers ask.
What class and grade do you apply?
Whichever your order calls for, within ASTM B841. Class, type and grade come from the specification your end client wrote, not from a menu on our side — including grade 10, which is the minimum 10 µm that offshore bolting specifications typically require. Send the drawing and the standard and our sales team returns the complete designation.
Why does the nickel content matter so much?
12 to 16% nickel is the range ISO 4042:2022 fixes. Below it the coating loses much of its corrosion resistance; above it the deposit turns brittle and adhesion suffers. The difficult part is that none of this is visible: colour, gloss and thickness look identical either way. That is why the alloy is measured by X-ray fluorescence during the process — a thickness reading alone tells you nothing about the alloy, and it is the alloy that corrodes.
I specified ASTM B841 grade 10. What if I need more resistance?
It is the same zinc-nickel, deposited — what changes is the structure of the layer, not the material. Nanostructured zinc-nickel, under the ASTM B1025-25 specification, is what we apply as NanoGalv®: from 10 µm the Modumetal test in ASTM B117 records over 10,000 h to red rust. The part, the thread and the drawing do not change — only the line it runs on.
Do the parts need hydrogen embrittlement relief?
High-strength steel absorbs hydrogen in the electrolytic bath and can crack later, already installed. When the material calls for it, heat treatment is a mandatory step with a record — ASTM B849 for stress relief before, ASTM B850 for hydrogen embrittlement relief after, to the standard and class your specification determines. It is not an optional finishing item.
Which passivation colours are available?
Trivalent white, black or clear, with no loss of protection. Colour is a matter of visual identification and of your client specification, not a performance indicator — protection comes from the alloy, the thickness and the sealant.