Oil Foaming

Sorry for the Shouting down of your question UsmanS. It is a good question for this ENGINEERING forum.

How foaming of oil occurs?

In old oils in use, Foaming generally starts because of a reaction between water and the steel parts that creates ferric hydroxide. This ferric hydroxide being basic, then reacts with various acidic components in the oil (The sulfur and phosphorous additives are acidic) and upon reaction with ferric hydoxide, create reaction products Various metalic salts)which form Foam.

It is not the water itself, but the water having attacked the steel that creates the foaming. It is the reaction products! Taking new oil and water, will not get you foam.

Once you know that it is the metal salts that cause the foam, you now have a way to chemically determine when to replace the oil...

And since we now know the role of water in the creation of the foaming problem, we can formulate additives (Specifically dehydrating agents) to tie up the water to prevent it from acting on the steel or ferrous parts in the gear drive, etc..Depending on the make up oil, anhydrous sulphates of potassium or sodium, or calcium oxide or annhydrous calcium chloride being inorganic will tie up the water, but being ionic, will not dissolve in oil. if particle size is fine enough, they will disperse keeping the water /metallic salts in a form not capable of promoting foaming. (there are other ways besides these)

What will be the effect on foaming of mixing of two oils?

Pretty broad question, but I will attempt to use my above reasoning to guide you to a conclusion.

1) if the oils are brand new, probably no foam;

2) If the oil(s) are old, and have had water contamination, and were used in a gearbox or device with steel parts, then depending on age of oil and the level of ferric hydroxide, foaming might occur.

3 As others have pointed out, you are now free to do a trial, and also by the way know several things to look for in the oil in order to understand what contributes to foaming.

Hope this helps, and do let us know how things work out.

Milo