How does coating thickness affect arc anodizing pricing?
Increasing arc-anodizing thickness can raise price by extending line occupancy, changing electrical and cooling demand, reducing usable load density, adding dimensional finishing, and increasing verification work. The increase is not governed by a universal linear or exponential formula. MAO/PEO growth depends on substrate, electrolyte, electrical program, geometry, bath condition and the coating architecture being controlled. A supplier must model the requested range on the actual part before converting thickness into price.
Thickness is not the same as functional performance
A thicker ceramic layer does not automatically provide proportionally better wear, corrosion or dielectric behavior. Wear also depends on phase structure, roughness, pores, substrate support, counterface, load and lubrication. Corrosion may depend on connected porosity, edges, substrate defects and the final sealer or topcoat. Dielectric failure is often local, so average thickness can miss a pore, rack contact or sharp edge.
Begin with the failure mode and test. Then identify whether thickness is a design input, a process-control characteristic or the final acceptance criterion. This prevents a drawing from purchasing additional coating that does not improve the required function.
A narrow range can cost more than a higher nominal target
Price is influenced by both nominal thickness and allowed variation. A tight band across open faces, recesses, edges and machined transitions may require more development, mapping, conservative processing or post-finishing. A broader range at nonfunctional zones can provide manufacturing room without weakening the component requirement.
Define zones separately. A wear land may need controlled thickness and roughness after grinding, while an internal noncontact surface may accept broader variation. Exclude permitted rack contacts from coating criteria. The processor should confirm which surfaces can be measured reliably with the selected method.
Growth behavior is route-specific
As MAO/PEO develops, discharge behavior and growth rate can change, but the pattern is not identical across alloys or equipment. A high-pressure aluminum casting with silicon-rich phases and pores may not follow the same window as wrought aluminum. Magnesium and titanium require their own systems. Even two processors can use different proprietary routes to meet the same finished requirement.
For this reason, a price estimate should not use a generic minutes-per-micrometer rule. Ask the supplier whether the target sits inside an established production window, at its edge or outside it. A target outside the approved window may trigger development rather than a simple cycle extension.
Where thickness changes cost
| Cost path | Possible thickness effect | Buyer control |
|---|---|---|
| Core processing | Different line occupancy, electrical program or cooling burden | Use the minimum supported architecture and qualified range |
| Load design | Spacing or area limit may change for the selected route | Confirm pieces per rack and full-load assumption |
| Dimensions | Growth and variation affect fits, threads and sealing lands | Mark whether dimensions apply before or after the final stack |
| Finishing | Grinding, polishing or selective removal may be needed | Specify only functional roughness and removal zones |
| Verification | More locations, sections or calibration work may be required | Define method, sample plan and qualification versus routine tests |
Measurement method belongs in the price request
Rough, porous or compositionally complex coatings can challenge some nondestructive thickness methods. Calibration must match the substrate and coating system. Cross-sectional measurement is destructive and sensitive to specimen preparation and location. The drawing should name or reference the method and show the measurement zones.
If cross-sections are required per lot, the quote must include sacrificial parts or witness samples, preparation and reporting. If destructive mapping is only for qualification, keep it out of routine unit pricing and replace it with an approved production control. Measurement burden can otherwise become larger than the incremental coating burden.
Dimensional planning prevents hidden thickness cost
State whether a finished dimension is required after MAO, after sealing, or after grinding. Threads and precision bores may be masked, machined beforehand with allowance, or locally finished afterward. Each route has different fixture, inspection and rework implications.
Coordinate the coating drawing with CNC machining. Do not apply one assumed growth factor to every surface. Validate specified fits on production-intent parts, including coating variation and any final finishing process.
Use functional trials to choose the economical range
Run representative samples at candidate architectures, then test the actual function. For wear, hold counterface and conditions constant. For corrosion, test the final sealed or topcoated stack and rate the specified failure. For dielectric use, test relevant electrode geometry and locations. Compare results with dimensions, roughness and process stability.
The selected range should be the one that repeatedly passes with adequate manufacturing margin, not the highest value the supplier can produce. Ask for separate development and production pricing if the range has not been qualified. The arc-anodizing classification framework can keep architecture and test scope aligned while suppliers quote different process settings.
Control thickness changes after approval
A later drawing change to nominal thickness, tolerance band or measurement location can affect fixture loading, dimensions, post-finishing and inspection even if the coating name stays the same. Route the change through both the processor and the part designer. Identify whether existing qualification still covers the revised range or whether targeted sections and functional tests must be repeated.
Retain approved reference parts and records from the production-intent trial. They help distinguish normal architecture variation from a material, surface-preparation or process shift. With that baseline, the supplier can quote a thickness change from evidence rather than treating it as a simple multiplier or reopening the entire program without justification.
