Ano
Article · Finishes
What Is Clear Anodized Aluminum?
Clear anodized aluminum is an anodic coating with no dye added, called Class 1 on a MIL-A-8625 drawing. It leaves the metal looking like itself, a little brighter and a little more matte, with real corrosion and wear protection over it.
What Clear Actually Means
Clear is not a color that gets applied. It is the absence of one. The anodic coating is naturally transparent, so a part that skips the dye step shows the aluminum underneath through a protective ceramic layer.
On a MIL-A-8625 drawing this is Class 1, non-dyed. The finished part reads as a slightly brighter, slightly more matte version of the metal that went in, because the etch step early in the process gives the surface a soft uniform texture.
What It Is Good At
Corrosion protection, without changing how the part looks. That combination is why clear is specified so heavily on machined parts that live inside equipment, where nobody needs them to be black but everybody needs them not to corrode.
It also adds very little dimension. A typical Class 1 Type II coating sits in the ten-thousandths of an inch, which most parts absorb without any drawing change at all.
And it hides nothing, which is occasionally the point. On a part where you want to see the machining, clear protects it without covering it.
Where It Disappoints People
Clear is faithful. Machining marks, tool chatter, scratches from handling and uneven bead blasting all remain visible, and the etch tends to reveal them slightly more rather than less. If the surface underneath is inconsistent, a clear finish will show it.
It also varies with alloy more visibly than dyed finishes do, because there is no dye to even things out. Parts cut from different alloys, or different heats, can read differently side by side. Black is far more forgiving on both counts, which is worth knowing before choosing.
Clear or Black, and How to Choose
Clear is the right answer when you want the part to look like metal, when appearance is secondary to protection, or when you specifically want the machining visible. It is also marginally simpler to run, since it skips the dye step entirely.
Black is the right answer whenever consistency matters more than showing the material. Dye evens out variation between alloys, heats and surface finishes, so a black assembly built from mixed material will look far more uniform than the same assembly in clear. Black also hides handling marks acquired later in service.
The mistake we see most is choosing clear on a cosmetic assembly built from parts of different origins, then being disappointed that they do not match. Clear shows you exactly what you gave it, which is a virtue on a single part and a liability across a set. See Type II Anodizing for the process and the alloys guide for what different materials do.
Common Questions
Is Clear Anodizing the Same as Type II Class 1?
On a MIL-A-8625 drawing, yes. Class 1 means non-dyed, and Type II is the standard sulfuric process. A Type III Hard Coat can also be run non-dyed, though a dense Hard Coat comes out dark gray naturally rather than clear.
Does Clear Anodizing Change the Color of Aluminum?
Slightly. The etch gives a soft uniform matte texture, so the part usually looks a little brighter and less shiny than it did going in. It is not a color change so much as a texture change.
How Thick Is a Clear Anodized Coating?
Typically in the ten-thousandths of an inch for a Class 1 Type II coating, so about half of that grows outward per surface. Most parts absorb it without a drawing change; close-tolerance features still need the allowance.
Will Clear Anodizing Hide Machining Marks?
No, and it tends to make them slightly more visible. Anodizing is faithful to the surface underneath. If appearance matters, the surface preparation before finishing matters as much as the finishing.
Is Clear Anodizing Cheaper Than Color?
It is generally the simplest to run since it skips the dye step, though the difference is rarely the deciding factor. We quote from the print and the count rather than from a per-color rate, so send the drawing for a real cost.
Keep Reading
Have a Part That Needs Finishing?
Send the print and the count. Standard turnaround is 3 to 5 days from our dock in Paoli, Indiana.