Metal finishing Q&As since 1989

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Synthetic Oil Reacting with Galvanizing

2004

I am researching a problem for a mechanical engineering company, who believe they are having problems with compressor oil reacting with hot dipped galvanizing. The engineer described it very technically as a "snot" like substance, but I was unable to see the sample myself. I have found some information regarding the saponification of the oil due to the alkaline state of the galvanizing, but the information was limited. It does however seem to fit the description of the effect on the oil. The oil is at about 100 degrees, and would most probably contain some water. I was hoping someone here may have heard of this problem. The oil used is synthetic compressor oil.

Regards,

Troy

p.s. They are also considering running coolant through this same section of material, consisting mostly of water and rust inhibiting products.

Troy Holdsworth
student - Perth, Western Australia

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2004

Dear Troy,

The problem is most likely caused by an organic acid resulting from the breakdown of the compressor oil in contact with water. The acid reacts with the galvanizing to form a metal/organic compound. If you research "greases" you will find that these compounds are used as a component in greases and you will find out more about their chemistry.

The solutions are to either change the oil frequently or find an oil which is stable in contact with water.

Regards,

John Carlotto
E. Providence, Rhode Island