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Fungus Formation on Cast Aluminum

2004

Sir,

We are manufacturers of Oil Pump for Two wheelers. We have come across Fungus(White rust?) formation.The occurance level is less than 0.1 %. We use Pressure Die Cast Aluminium Body.The details are

1.Raw material-ADC 12
2.Process Sequence:

Pressure Die Casting
Shot Blasting(0.4 mm steel wire shots)
Machining(Water Soluble Oil)
Water Cleaning(Alkali Solution at 80 degree Centrigrade-Hextron M01)
Hot Air Cleaning

After Assy:
1.Flushing in turpentine ⇦this on eBay or Amazon [affil links] oil
2.Rust preventive Oil is applied

  

Can you explain the Phenomena or which chemical agent is the culprit.

Regards,

D.B.Prabhu ram
Sr Engineer - Coimbatore, Tamil Nadu, India

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Dear Sir,

I think you have to check the Alkaline cleaner, apart from the water in oil emulsion. Because, Aluminium being amphoteric will get attacked in both acids and alkali. Mild cleaners containing carbonates shall be used for alkaline cleaning and in preparation of emulsion use soft or DM water.

Shankara Narayanan N
- Bangalore, Karnataka, India
2004