Anodized Aluminum Surface Defects - Stains, raised surfaces, imperfections

[Phil Fields]

Hello!
I have a question concerning anodized aluminum. Historically I have not had quality issues concerning the anodized aluminum parts that we purchase (made to company print). Recently we have been experiencing stains, raised surfaces, surfaces imperfections, etc.
Is there a standard/preferred surface preparation that should be performed prior to the anodize process?

Thank you,
Phil

[ScottK]

In Reply to Parent Post by Phil Fields

Hello!
I have a question concerning anodized aluminum. Historically I have not had quality issues concerning the anodized aluminum parts that we purchase (made to company print). Recently we have been experiencing stains, raised surfaces, surfaces imperfections, etc.
Is there a standard/preferred surface preparation that should be performed prior to the anodize process?

Thank you,
Phil

I'm not an expert at anodizing, but have put a lot of time into dealing with anodizing issues over the last few months...

Sounds like your anodizer might be using a dirty bath and contaminent is getting in. Or perhaps he's not cleaning the parts properly prior to hitting the anodizing tub. We send our parts with a left over coating of cutting oil that the anodizer cleans them off in an ultrasonic bath.

We typically see "staining" in parts where condensation may sit after the dye bath. It appears as discolored spots.
We've also seen surface imperfections from dirt that didn't get cleaned off the part.
I'm not sure by what you mean by "raised surfaces"...

[Phil Fields]

Scott,
Thanks for the reply. The raised surfaces, I think is caused by dust/dirt that is be anodized over. My opinion is that the processor is not cleaning properly. Before I try to work with the supplier I need to educate myself a little bit to direct the supplier in the right direction.

Phil

[ScottK]

In Reply to Parent Post by Phil Fields

Scott,
Thanks for the reply. The raised surfaces, I think is caused by dust/dirt that is be anodized over. My opinion is that the processor is not cleaning properly. Before I try to work with the supplier I need to educate myself a little bit to direct the supplier in the right direction.

Phil

you know - another thing we get on occasion is "burning" around where the contacts touch the part. This has caused pits in the aluminum.
Many of our parts are held on "trees" with something like tweezers in reverse.

Out of curiosity - is your anodizer consistent with color between and within batches? That's a problem area for us.

[Phil Fields]

In Reply to Parent Post by ScottK

you know - another thing we get on occasion is "burning" around where the contacts touch the part. This has caused pits in the aluminum.
Many of our parts are held on "trees" with something like tweezers in reverse.

Out of curiosity - is your anodizer consistent with color between and within batches? That's a problem area for us.

Scott,
Color is consistent, we have only had a few issues with a shade difference.

Phil

[andygr]

They have process line problems in more than one area based on what you describe.
There are specs such as Mil 8625 that cover process control and testing.

[ScottK]

In Reply to Parent Post by andygr

There are specs such as Mil 8625 that cover process control and testing.

True - but there's a lot of anodizers/platers, at least in this area, that quite literally work out of their garages.
The reponse from them is "Mil what now?"

[andygr]

In Reply to Parent Post by ScottK

True - but there's a lot of anodizers/platers, at least in this area, that quite literally work out of their garages.
The reponse from them is "Mil what now?"

Which is why you see the things that were mentioned from these types of opperations. As we all know it comes down to cost vrs quality. You just need to figure out what the balance is for your application.