How to make aluminum surface finish more scratch resistant?

[funtech]

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

 

[ctopher]

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

 

[Occupant]

Sulfuric Acid Anodize.

 

[KENAT]

So called hard anodize will be fairly scratch resistant, but you're typically limited to dull black finish.

Posting guidelines faq731-376

http://eng-tips.com/market.cfm?

(probably not aimed specifically at you)
What is Engineering anyway: faq1088-1484​

 

[MikeHalloran]

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

 

[MintJulep]

GRade and temper are important too.

What are you using?

 

[funtech]

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.

 

[TVP]

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.

 

[Compositepro]

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.

 

[tbuelna]

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.