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How to make aluminum surface finish more scratch resistant?

How to make aluminum surface finish more scratch resistant?

How to make aluminum surface finish more scratch resistant?

(OP)
In a product I'm developing, the housing is to be made of aluminum. For the prototype, I had them sandblast and anodize it. While it looks beautiful (like the back of a Iphone), the surface is very easy to scratch.

I thought anodizing is supposed to make it more scratch resistant. Then again, I'm not an expert on anodizing and I've heard there are different types. For my prototype, I didn't use any color because I like the natural metallic look. But I've seen anodized aluminum with a black or colored finish that seems to hold up better to scratches.

I'm thinking rather than a sandblasted finish, how about a brushed finish. I would think scratches are less noticeable on a brushed metal finish (camouflages better) , what do you think?

thx

RE: How to make aluminum surface finish more scratch resistant?

Talk to the anodize vendor about the alum finish before anodize. A thin anodize can scratch. Try a thicker anodize.
A brush finish may show through.

Chris, CSWA
SolidWorks 14
ctopher's home
SolidWorks Legion

RE: How to make aluminum surface finish more scratch resistant?

Sulfuric Acid Anodize.

RE: How to make aluminum surface finish more scratch resistant?

Anodize is really a micro-cracked ceramic, but the default is vanishingly thin, and the substrate is still soft aluminum. Leaving the part in the anodizing process longer gives a thicker, more durable finish, but of course the time and electricity costs the anodizer money, so you have to pay more.

Always specify a dyed/colored anodize, or you will suffer recurring problems with UN-anodized parts being confused with clear-anodized parts. This, I know.



Mike Halloran
Pembroke Pines, FL, USA

RE: How to make aluminum surface finish more scratch resistant?

GRade and temper are important too.

What are you using?

RE: How to make aluminum surface finish more scratch resistant?

(OP)
They used 6061 aluminum. I wonder if using a harder aluminum alloy would also help?

On balance, I think a thicker anodize is probably the best option.

RE: How to make aluminum surface finish more scratch resistant?

Harder alloys like 2024 and 7075 do not anodize as well as 6061, and so it is unlikely that this will improve your situation. A thicker anodized layer should be your first course of action.

RE: How to make aluminum surface finish more scratch resistant?

Keep in mind that the hard anodize produces a less porous coating which makes dying more difficult. The key for good color is uniform porosity.

RE: How to make aluminum surface finish more scratch resistant?

As you noted, applying a brushed finish to the aluminum surface prior to anodizing will help "hide" scratches. You might also try using a PTFE infused hard anodize coating.

If you can afford the cost, you can use black electroless nickel plating, which is very hard and durable.

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