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Blue pitting on the downward surface After Electropolish

2005

Dear All:
We are conducting a new technics to ECP (Electropolish) our Aluminium parts.But we had found some blue pitting on the downward surface after ECP .Our electrolyte is mixed with phosphoric acid ,sulfuric acid and citric acid ⇦ this on eBay or Amazon [affil links] ,the working temperature is 90~100.
If anybody know what had happened, please give me some suggestions. Will thanks and appreciate for your opinions.

Richard
- ShenZhen,China

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Richard,
Have you analyzed the solution for aluminium maybe you have a high contents of aluminium in the solution.

Regards

Anders Sundman
4th Generation Surface Engineering
Consultant - Arvika,
Sweden
2005

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Dear Anders:
Thanks for your attention firstly.We had tested the content of Aluminium, it is 12 g/l.Normally,we should renew 1/3 solution when the content achieve 20 g/l. Do you agree with it? Another case, whether we should consider the effect of current density or not? Waiting for your further proposal.


Best regards,and thanks!

Richard
- ShenZhen, China
2005

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Richard.
If I remember right you should not have more than 10 g per litre of aluminium in your solution.

Regards

Anders Sundman
4th Generation Surface Engineering
Consultant - Arvika,
Sweden
2005

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Dear Anders:
We had done like what you had said. The performance become better. But our cost raised and efficiency debased. Because our average output per-day is 60K. If do like that,we will renew the solution half of the day. Do you know is there any better way? Will appreciate for your further proposal.

Richard
- ShenZhen, China
2005

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First of two simultaneous responses --

Richard,
I think the only way is to renew the half of solution.

Good Luck

Anders Sundman
4th Generation Surface Engineering
Consultant - Arvika,
Sweden
2005

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Second of two simultaneous responses --

Not an expert by any means but could the electrolyte agitation be increased.

Gary Levesque
- Hyannis, Massachusetts
2005

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First of two simultaneous responses --

Hi Gary.
Good input--yes it should help. But I believed from the beginning that he has that in the solution.

Regards,

Anders Sundman
4th Generation Surface Engineering
Consultant - Arvika,
Sweden
2005

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Second of two simultaneous responses --

Anders:
Thanks for your further concern. In initial stages, we had renew our solution frequently to stabilize performance of the electrolyte. But recently we had found cycle-life would be prolonged if we reduced the dosage of sulfuric acid and no blue pitting was found on the downward surface. Can you tell me what had happen? And what did the sulfuric acid act as in this electrolyte system?Very appreciate and look forward to your further guidance!


Best regards,and thanks!

Richard
- SenZhen, China
2005

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2005

I think the phosphorous acid will build complex with the aluminium easier than sulfuric acid there for will phosphorus acid be too old and contamination before sulfuric acid in the solution. Bough sulfuric and phosphorus acid will help in the solution to polish the aluminium.

Regards,

Anders Sundman
4th Generation Surface Engineering
Consultant - Arvika,
Sweden

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2005

Dear Anders:
I sorry that I have a little confusion for the "Bough sulfuric".Can you tell me what is it?Will look forward to your reply.Thanks!

Best regards,and thanks!
Richard

Richard
- ShenZhen, China

We believe that this was a typographical error and Anders meant to say "Both sulfuric and phosphoric acid will help . . ." Hopefully he'll see your message and clarify this.

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Ok,
I mean both sulfuric acid and phosphoric acid works together in the electro polish solution but phoshoric acid have the tendency to build a complex with aluminium contamination. Therefore works your solution better if you only fill up the solution with new phosphoric acid. But you must also made a analyze for the sulfuric acid. I'm also believe at the sulfuric acid will give the electrolyte a electric conducting current. I hope you understand me and. You can read more about electro polishing in AMS volume 5 book.

Regards,

Anders Sundman
4th Generation Surface Engineering
Consultant - Arvika,
Sweden
2005

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2005

Dear Anders:
Thanks for your kindly guidance.Normally when we fill up phosphoric acid,in the mean time ,we also add sulfuric acid into the solution,but we didn't analyze the concentration of H3PO4 and H2SO4,we only do testing for the citric acid .Did we make a mistake?How do you think when we fill up the solution whether we need to add corresponding citric acid or not?And do you have better way to analyze the H3PO4 and H2SO4 in this solution?Any suggestion will be much appreciated!

Best regards!

Richard
- ShenZhen, China