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When Sections are blasted for anodizing is brightening process necessary?

March 16, 2011

Dear Sir,
I am doing anodizing. Recently someone suggested we go for mechanical etching. For that purpose we are planning to buy a shot blasting machine, where aluminium will be blasted with certain media to get it good matte finish. But some are telling me that I should go for brightening process after the blasting while some people say that brightening process won't matter a lot. I am really confused. I really can't increase brightening process in my line. So my questions are as follows:-
1) Is it very necessary to do brightening after blasting of sections?
2) What will happen if I don't do brightening?
3) I have been told that even hot etching with caustic will solve the purpose and it won't matter a lot. Is it true?
4) Brightening process contains nasty chemicals at high rate which are difficult and costly to handle so we can't go for brightening process.

Thanking you all in anticipation your replies are really valuable. Please guide me through this problem

Bhagyashree Karnawat
Plating shop - Pune Maharashtra India

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Hi Bhagyashree,

It really comes down to what your customers want. Do they want a bright or matte finish? If it is the former then you will need to have a bright surface to anodise, so don't blast or use caustic solutions. If it is the latter then you can use various methods to dull down the surface including blasting or a caustic treatment.

Brian Terry
Aerospace - Yeovil, Somerset, UK
March 17, 2011

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Hi Brian,
Thanks a lot for your reply. My customer wants satin matte finish. For that purpose I am doing blasting to dull it down. My main problem is that whether shall I do brightening after blasting or should I just anodize it. I am in this state of confusion. Actually due to caustic etching many times we get shade variation in the output as we are unable to monitor the concentration of caustic for that reason we are diverting to blasting.
Waiting for more replies

Bhagyashree Karnwat
- Pune Maharashtra India
March 18, 2011

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Hi, Bhagyashree.

I think the point that Brian was making is that you can't take a loose and vague description of the desired appearance of an item, like "satin matte", and parlay that into a detailed process sequence that will produce what the customer wants without knowing what the customer wants :-)

One person will look at your "etch only" parts and say "that's not what I meant; where's the satin?", while another will look at your "etched and brightened" parts and say "I asked for matte, not for bright". You are not going to solve this issue without sending sample parts to your customer for his agreement as to what the finish should look like Good luck.

Regards,

Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
March 17, 2011

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Thanks Ted,
I think you are right. I want to ask one more thing actually we are going for airless shot blasting machine. I have heard that we can't use glass beads on airless type blast machine. Is it true? What type of media you suggest for airless type blast machine. I really appreciate your follow up over the matter.

Bhagyashree Karnwat
- Pune Maharashtra India
March 19, 2011

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Hi, Bhagyashree. Sorry, I don't know whether glass beads are compatible with airless blasting.

Regards,

Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
March , 2011

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Thanks Ted. I will have to do exercise over this. If you come across solution please let me know.
Regards.

Bhagyashree Karnawat
- Pune Maharashtra India
March 22, 2011