Zinc-Nickel vs. Cadmium Plating: Which Should You Specify?
How does corrosion protection compare?
Both coatings protect steel sacrificially — they corrode preferentially, so the substrate is protected even at scratches and cut edges. Chromated cadmium per AMS-QQ-P-416 Type II must show no white corrosion after 96 hours of neutral salt spray, with red-rust protection scaling with thickness class. High-alloy zinc-nickel (12–16% Ni) per AMS 2417 with a trivalent passivate is typically specified at 500 hours without red rust, and good deposits test out to 720–1,000 hours. On raw salt-spray numbers, zinc-nickel wins, and it also holds up better at elevated temperatures, where cadmium’s protection falls off above roughly 450°F.
What about hydrogen embrittlement?
Cadmium plating is an embrittling process. AMS-QQ-P-416 requires steels at HRC 40 and above to be baked at 375°F for 23 hours, starting within 4 hours of plating — a hard constraint on lead time and a permanent risk item on landing gear-class hardware. Alkaline zinc-nickel is a low-hydrogen-embrittlement (LHE) process, one of the main reasons aerospace qualified it as the cadmium replacement. High-strength parts still get a relief bake per ASTM B850, but the intrinsic hydrogen load is lower.
Where do RoHS and environmental rules come down?
Cadmium is a toxic heavy metal, restricted under RoHS, ELV, and REACH; it survives only under aerospace/defense and certain electrical exemptions. Zinc-nickel with trivalent passivate is fully RoHS compliant. If your product has any commercial or export exposure, zinc-nickel is the safe long-term callout; cadmium locks you into exemption-dependent supply.
Is zinc-nickel a true drop-in replacement for cadmium?
Mostly, with known gaps. Zinc-nickel matches or beats cadmium on corrosion, temperature, and embrittlement risk. Where it falls short: cadmium’s natural lubricity gives more consistent torque-tension behavior on threaded fasteners (zinc-nickel usually needs a supplementary lubricant or topcoat to match), and cadmium’s galvanic compatibility with aluminum is slightly better, though high-alloy zinc-nickel is close. Solderability also favors cadmium. “Drop-in” is true for most brackets, housings, and structural hardware; fasteners and electrical contacts deserve an engineering look rather than a global find-and-replace.
When is cadmium still the right call?
Three cases. First, legacy drawings: if the part is qualified with cadmium and requalification is impractical, you run cadmium. Second, threaded fasteners where torque-tension consistency is flight-critical and the joint was engineered around cadmium’s friction behavior. Third, connectors and electrical hardware where cadmium’s low, stable contact resistance and solderability are baked into the design. Outside those, new designs should specify zinc-nickel.
How do costs compare?
Per-part plating costs are broadly comparable; zinc-nickel chemistry costs more to operate, while cadmium carries heavier waste-treatment, compliance, and (for HRC 40+ steel) 23-hour bake overhead. The bigger cost driver is availability: cadmium capacity keeps shrinking as shops exit the chemistry, which shows up as longer lead times and freight to distant suppliers. That scarcity, not the rack price, is what usually hurts.
Side-by-side comparison
| Attribute | Zinc-Nickel (AMS 2417 / ASTM B841) |
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| Salt spray (chromated) | 500+ hrs to red rust typical |
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| Sacrificial protection | Yes |
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| Hydrogen embrittlement risk | Low (LHE alkaline chemistry); bake per B850 on high-strength steel |
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| RoHS/ELV/REACH | Compliant (trivalent passivate) |
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| Elevated temperature | Good to ~500°F |
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| Fastener lubricity / torque-tension | Needs topcoat/lube to match |
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| Galvanic fit with aluminum | Good (high-alloy) |
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| Availability | Growing |
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Frequently Asked Questions
Can I replace cadmium with zinc-nickel on an existing drawing?
Only with an approved drawing change or customer disposition — the finisher must plate what the drawing calls. Many primes have published cadmium-to-zinc-nickel substitution paths (typically to AMS 2417); your customer’s engineering authority decides, not the plater.
Which is cheaper, zinc-nickel or cadmium?
Rack prices are comparable; total cost usually favors zinc-nickel once cadmium’s bake time, compliance burden, and shrinking supplier base are counted. For high-strength steel, cadmium’s mandatory 23-hour bake alone adds a day to every lot.
Does anyone in Texas plate both?
Very few shops run both chemistries — Gleco Plating does: zinc-nickel at both Texas plants (Rowlett and McAllen) and cadmium at our McAllen plant, under an AS9100D / ISO 9001:2015 quality system with ITAR registration and DFARS compliance. That means legacy cadmium work and new zinc-nickel work ship from one supplier on one PO.
Get both finishes from one Texas supplier
Gleco Plating runs zinc-nickel (low- and high-alloy, to AMS 2417 and ASTM B841) and cadmium (to AMS-QQ-P-416) side by side, with in-house chemists controlling both lines. If you are supporting legacy cadmium drawings while transitioning new designs to zinc-nickel, send both to one accountable supplier. Request a quote or send us your finish callout and we will confirm the spec, class, and bake requirements before you cut the PO.
