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coral-like structure growing on aluminum diecasted part - what causes it

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Andon

Automotive
May 23, 2019
2
Hello Community,

I am currently performing some field tests of aluminum (AlSi10Mg) diecasted parts, which after assembly become water pump, which ,of course, is usually always floating in not salty water.
After few weeks in a nearby lake I saw it grew many coral-like structures. I can't explain to myself why is this happening, I certainly didn't have this in the past, the water quality didn't change at all.
I am suspecting our supplier changed something regarding the surface treatment.

Any advice what might be the nature of this phenomenon will be very hepful.

Thank you!

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