Electroplating Specifications.
Electroplating specifications define the technical requirements, quality standards, thickness ranges, and performance criteria for plated coatings across industries. These specs guide manufacturers and electroplating suppliers in delivering consistent, reliable metal finishes that meet engineering, durability, and compliance needs.
- SAE AMS 2404
- SAE AMS 2413
- SAE AMS 2422
- SAE AMS 2425
- SAE AMS 2460
- SAE AMS 2465
- SAE AMS 2470
- SAE AMS 2481
- SAE AMS 2485
- SAE AMS 2490
- SAE AMS 2495
- SAE AMS 2500
- SAE AMS 2510
- SAE AMS 2520
- SAE AMS 2530
- SAE AMS 2540
- SAE AMS 2550
- SAE AMS 2560
- SAE AMS 2570
- SAE AMS 2580
- SAE AMS 2590
- SAE AMS 2600
- SAE AMS G 2418
- SAE AMS P 81728
- SAE AMS QQ N 290
- BMW GS90010
- Columbia Chemical GMW 4700 ZNNI Type B
- Cummins 74052
- Ford WSS M1P87 B5
- GM GMW4700
- Honda HES D2003 MFZN NI1 K
- Hyundai Kia MS611 15
- Jaguar Land Rover STJLR 50 5058
- Mazda MES CG310
- Mercedes DBL 8451
- Stellantis PS 50045
- Stellantis PS 50065
- Tesla TM 0009F M 10
- Toyota TSH6530G
- Toyota TSH6532G
- Volkswagen TL 244
- Volkswagen VW 4301
- Volkswagen VW 4320
- Volvo STD 121 0003
Military Cadmium Standard: Active military specification for cadmium plating protecting high-strength steel from corrosion despite environmental concerns.
Summary
MIL-DTL-14538 is the current military specification for cadmium electroplating on steel and aluminum alloys. It replaces older MIL-C-8837 and QQ-P-416 covering sacrificial corrosion protection for military hardware and aerospace fasteners. Cadmium's banned for most commercial uses due to toxicity but military allows it because nothing else protects high-strength steel fasteners as well in salt fog environments. The spec defines thickness classes, finish types, and hydrogen embrittlement relief requirements. Restricted to defense and aerospace applications where cadmium's superior performance justifies environmental headaches.
Coatings
MIL-DTL-14538 covers cadmium electroplating providing sacrificial corrosion protection for military fasteners and aerospace components. Toxic but technically superior for high-strength steel in harsh environments.
- Cadmium (not in database - military/aerospace only coating)
Requirements Overview
MIL-DTL-14538 organizes cadmium plating by type (substrate material), class (thickness), and finish (chromate treatment). Type I is steel, Type II is aluminum alloys. Classes define minimum thickness from 5 to 25 microns. Finish O is olive drab chromate, Finish C is clear. Supplementary requirements cover hydrogen embrittlement relief and testing. The spec's strict about thickness uniformity since military fasteners can't tolerate dimensional variations affecting thread fit.
Type I
Cadmium on steel and steel alloys. Most common application covering military fasteners, landing gear components, and weapons systems hardware. Sacrificial protection preventing steel corrosion in salt spray and harsh field environments.
Type II
Cadmium on aluminum and aluminum alloys. Less common than Type I but used where galvanic protection needed for aluminum structures. Naval aircraft and shipboard electronics applications requiring aluminum corrosion protection.
Class 1
5 microns (0.0002 inch) minimum. Lightest coating for mild environments or when dimensional tolerances tight. Interior aircraft components or electronics hardware with limited corrosion exposure and strict size requirements.
Class 2
8 microns (0.0003 inch) minimum. Standard thickness for most military fasteners and general hardware. Balanced corrosion protection without excessive dimensional buildup. Most specified class for aerospace applications balancing performance with fit.
Class 3
12 microns (0.00047 inch) minimum. Heavy-duty protection for severe marine or industrial environments. Shipboard hardware, offshore platforms, and exposed aircraft surfaces requiring maximum sacrificial protection from salt spray.
Class 4
25 microns (0.001 inch) minimum. Thickest coating for extreme corrosion protection when dimensional increase acceptable. Large structural components, landing gear, or hardware with generous tolerances needing extended service life.
Finish O
Olive drab (greenish-brown) chromate conversion coating over cadmium. Standard military finish providing additional corrosion resistance and signature reduction. Most commonly specified for visible hardware and tactical equipment requiring camouflage appearance.
Finish C
Clear (colorless) chromate conversion coating. Used when appearance matters or electrical conductivity important. Electronics hardware, precision instruments, or applications where olive drab finish interferes with assembly or inspection operations.
Supplementary
Hydrogen embrittlement relief baking mandatory for high-strength steel (over 180 ksi tensile). Low embrittlement cadmium process options, torque-prevailing feature preservation, or additional testing for critical applications requiring enhanced quality controls.
Military Cadmium Selection: Choosing coating thickness and finish for defense applications where cadmium's performance justifies environmental concerns.
Requirements Selection
Class 2 with Finish O is default military fastener specification providing 1000+ hours salt spray protection. Class 3 for severe marine exposure on ships and offshore platforms. Class 1 when dimensional tolerance critical for precision mechanisms. Hydrogen embrittlement relief absolutely mandatory for high-strength fasteners (grade 8 and higher) preventing catastrophic failure. Clear finish (Finish C) specified for electrical contact surfaces or when olive drab interferes with inspection. Modern military increasingly explores cadmium alternatives but still uses MIL-DTL-14538 where proven performance required.
Underplate Layer Stacks
Cadmium plates directly onto steel without underplate since adhesion excellent and sacrificial protection mechanism requires electrical contact between cadmium and steel. Aluminum substrates sometimes use zinc immersion pretreatment before cadmium improving adhesion. No copper or nickel underplates used since they'd interfere with galvanic protection mechanism. Chromate conversion coating always applied after cadmium providing supplementary corrosion barrier and surface passivation preventing white corrosion product formation.
- Direct on Steel: No underplate needed
Cadmium electroplates directly onto clean steel surface without intermediate layers. Excellent adhesion and electrical contact necessary for sacrificial protection. Adding underplates would interfere with galvanic mechanism where cadmium corrodes preferentially protecting steel substrate underneath.
- Chromate Topcoat: Essential final treatment
Olive drab or clear chromate conversion coating always applied after cadmium plating. Provides additional corrosion barrier, prevents white corrosion formation, and improves paint adhesion. Chromate treatment is specification requirement not optional supplement. Defines finish appearance and enhances protection significantly.
- Aluminum Pretreatment: Type II activation
Aluminum substrates receive zincate immersion treatment before cadmium plating improving adhesion on difficult-to-plate alloys. Thin zinc layer provides nucleation sites for cadmium deposit. Required for Type II specifications on aluminum preventing adhesion failure from native oxide barrier.
Cadmium Specification Errors: Critical mistakes in military cadmium plating causing fastener failures or environmental compliance problems.
Common Mistakes
Most critical error is skipping hydrogen embrittlement baking on high-strength fasteners causing delayed brittle fracture. Specifying cadmium for commercial products violates environmental regulations since it's restricted to defense and aerospace applications. Using insufficient thickness (Class 1) for marine environments leads to rapid corrosion failure. Missing that chromate treatment is mandatory part of specification not optional topcoat. Trying to substitute zinc or other alternatives without proper testing since military qualified cadmium for good reasons.
Skipping Hydrogen Embrittlement Relief
Catastrophic mistake for high-strength fasteners (over 180 ksi tensile strength). Hydrogen from plating process causes delayed brittle fracture under stress. MIL-DTL-14538 requires post-plate baking within 4 hours at specific temperature and time. Missing this supplementary requirement causes field failures killing aircraft and personnel. No exceptions for high-strength hardware.
Commercial Application Attempts
Cadmium is restricted to defense and aerospace applications under environmental regulations. Specifying MIL-DTL-14538 for commercial products violates cadmium usage restrictions in most jurisdictions. European RoHS, California Prop 65, and EPA regulations prohibit cadmium in consumer goods. Military and aerospace exemptions don't extend to commercial products regardless of specification reference.
Insufficient Thickness for Environment
Class 1 or 2 cadmium inadequate for shipboard or offshore applications. Marine salt spray demands Class 3 minimum for reliable service life. Underspecifying thickness to save weight or cost results in premature corrosion failure. Salt spray testing proves thickness requirements aren't negotiable for severe environments. Match class to actual exposure severity.
Treating Chromate as Optional
Chromate conversion coating (Finish O or C) is mandatory specification requirement not optional topcoat. Cadmium without chromate treatment fails specification and shows poor corrosion resistance compared to properly finished parts. White corrosion forms rapidly on bare cadmium. Chromate passivation essential for meeting salt spray requirements and achieving specification compliance.
Casual Substitution Attempts
Military specified cadmium after extensive testing proving superior performance for high-strength fasteners in salt fog. Substituting zinc, zinc-nickel, or aluminum coatings without proper qualification testing and military approval violates specifications. Alternative coatings improving but cadmium remains standard for critical aerospace fasteners where field failure unacceptable.
Conclusion
MIL-DTL-14538 is active military specification for cadmium electroplating on steel and aluminum providing superior sacrificial corrosion protection for defense and aerospace applications. Despite environmental concerns and toxicity, cadmium remains standard for high-strength military fasteners because nothing else delivers equivalent salt spray protection without risk of hydrogen embrittlement or galvanic compatibility issues. The spec's comprehensive covering thickness classes, chromate finishes, and mandatory hydrogen embrittlement relief. Restricted to military and aerospace applications where performance justifies environmental headaches. Commercial alternatives improving but cadmium still king for critical fastener applications.
Next Steps
Verify application qualifies for military cadmium exemption before specifying MIL-DTL-14538. Mandatory hydrogen embrittlement baking for all high-strength fasteners (grade 8 and above) without exception. Specify Class 2 minimum for general aerospace hardware, Class 3 for marine environments. Include Finish O (olive drab) unless clear chromate specifically required. Work with qualified military plating shops maintaining approval since commercial finishers can't process cadmium legally. Explore approved alternatives for new designs as military gradually reduces cadmium dependence.