Best Passivation Method?
Best Passivation Method?
(OP)
Here I have at my work place the passivation process.
It would work for most of the time with new solution but only last for a month or so and parts would start failing and the phosphoric acid would need to be change.
For more complicated parts (bigger and more edges/holes made from NC), it would fail very often even with new solution.
Wondering what would be the problem.
Here is general process
Electro Polish with current through 5 mins
Rinse
Phopsphoric Acid 5 mins
Rinse
Type 2 Passivate 30 mins
Rinse
Dichromate Treatment 30 mins
Rinse
Hot Water Seal 1 mins
Spin Dry
It would work for most of the time with new solution but only last for a month or so and parts would start failing and the phosphoric acid would need to be change.
For more complicated parts (bigger and more edges/holes made from NC), it would fail very often even with new solution.
Wondering what would be the problem.
Here is general process
Electro Polish with current through 5 mins
Rinse
Phopsphoric Acid 5 mins
Rinse
Type 2 Passivate 30 mins
Rinse
Dichromate Treatment 30 mins
Rinse
Hot Water Seal 1 mins
Spin Dry





RE: Best Passivation Method?
In the description of the process you do not mention any cleaning step. What cutting fluids are used and are they removed prior to the electropolish and passivation. Also what material are you working with.
Mark Hutton
RE: Best Passivation Method?
The only cleaning processes are Electro polish with current through part to remove excess oil; and soak in phosphoric acid to let it react and clean the rest of the part.
However problem we have is the process could be running well today and tomorrow parts will fail with same procedure. (FYI the chemical solution remain the same for both day with same % of acid).
RE: Best Passivation Method?
RE: Best Passivation Method?
RE: Best Passivation Method?
How soon after processing are you testing?
Give the parts overnight before you test.
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Plymouth Tube
RE: Best Passivation Method?
However we are never sure what happen when things started failing again.
Generally we test right away in salt spray chamber.
What is the reason behind testing after a night?
Thanks