Measuring Anodic Coating Thickness
Why Precision Matters
For manufacturers and engineers working with critical components in aerospace, defense, medical, or automotive industries, precision in anodic coating thickness can mean the difference between passing inspection and facing a costly recall.
Whether you're working with Type II anodizing for cosmetic finishes or hard anodizing for wear resistance, knowing the coating thickness (and ensuring it meets exact specs) is essential for quality, compliance, and durability.
Why Coating Thickness Accuracy Is So Important
Guesswork doesn’t fly in high-stakes manufacturing. A part with the wrong anodizing thickness can suffer from premature wear, poor corrosion resistance, or even dimensional issues that affect how components fit together. Here's why it matters:
- Performance: A coating that’s too thin may fail under stress or in harsh environments. Too thick? It might crack or interfere with part tolerances.
- Compliance: Aerospace and defense parts must meet strict anodizing specs like Mil-A-8625, AMS-2471, or AMS-2468. Thickness is a core requirement.
- Durability: Anodizing helps aluminum resist corrosion and wear, but only if the coating is applied at the correct thickness.
- Repeatability: Quality assurance depends on consistency. If your anodizing thickness varies too much, it throws off production runs and can create downstream problems.
In short, accurate measurement is essential.
How Is Anodizing Thickness Measured?
There are a few proven ways to measure aluminum anodizing thickness. The right method depends on the type of anodizing and the part being inspected.
1. Eddy Current Testing
This is one of the most common non-destructive methods used in the industry. It works best on non-conductive coatings over conductive substrates, perfect for anodized aluminum.
- Pros: Quick, accurate, and non-destructive
- Cons: May struggle with very thin coatings or irregular surfaces
2. Microscopic Cross-Sectioning
In this method, a small sample of the part is cut, mounted in resin, and examined under a microscope to directly measure the coating layer.
- Pros: Very accurate
- Cons: Destructive and time-consuming; not ideal for high-volume testing
3. Weighing Before and After
Known as the gravimetric method, this involves weighing the part before anodizing, stripping the coating chemically, then weighing again to determine thickness.
- Pros: Simple, good for lab use
- Cons: Also destructive, less practical in production settings
What’s the Right Thickness for Your Part?
Anodizing isn’t one-size-fits-all. The required coating thickness depends heavily on the application and environment. Here's a quick look at typical thickness ranges:
| Anodizing Type | Typical Thickness Range |
|---|---|
| Type II (Conventional) | 0.0002" – 0.001" (5 – 25 µm) |
| Hard Anodizing (Type III) | 0.001" – 0.004" (25 – 100 µm) |
If you're working with tight tolerances or specific design criteria, an anodize thickness chart can help guide your decisions. Just remember, coating thickness includes both internal (penetration) and external (build-up) layers. Only about 50% of the coating adds to the part's dimensions.
Standards You Can’t Ignore
In regulated industries like aerospace and defense, anodizing thickness must comply with national and international standards. A few of the most recognized:
- MIL-A-8625: The gold standard for military applications
- MIL-STD-171: Focuses on corrosion resistance and surface finish
- AMS-2471 / AMS-2468: Aerospace standards from SAE International
At LMC (Light Metals Coloring), we meet or exceed these specifications with every anodizing run. Our in-house quality systems and NADCAP-accredited chemical processing ensure you're getting results that match the drawing every time.
What’s at Stake if You Get It Wrong?
Let’s say your coating thickness is just a few microns off. That might not sound like a big deal, but in aerospace, that small error can mean:
- Seal failure
- Friction and wear issues
- Corrosion exposure
- Assembly fit problems
- Rework or scrap costs
Precision matters. Every time.
Keep Your Quality on Track
Precision in anodizing thickness is a necessity. Whether you're aiming to meet military standards or extend the lifespan of your components, accurate measurement is the foundation of consistent, high-quality results.
Need help getting it right? Contact LMC today. We’ll work with you to ensure your coatings meet all your technical, dimensional, and compliance needs.
Learn more about our anodizing services and certifications.
