Water in Petroleum products and other bituminous materials

This  method  is  intended for  use  in the  determination of water in bituminous  products  which  would  include  asphaltic  residua  used as  exposed gear  lubricants. A sample  of  the  product in  question is  diluted  with  a solvent  and  distilled  the  water  being  caught  in a  graduated  trap. Water in gear oils should only be present as a contaminant. A qualitative test  for  moisture  in gear  lubricants  consists of  holding  a  sample  in  a  beaker or  can  on a  hot  plate  and  when  the  temperature  reaches  about  212 degree F, observing  if  foaming  takes place.

Tests  for Other Characteristics of Lubricating Oils. Before  lubricating  oils  are  selected for  use  in  compounding  specific  types  of gear lubricants,  other  characteristics may  need  to  be  considered. For example, compatibility with   the other ingredients of a composition is very important. This and other qualities will be mentioned as need arises.

Demulsibility of gear oils

Lubricating oils vary in their tendency to emulsify with water; therefore, if emulsification of gear oils is likely to be a problem, the base oil should be investigated. Any polar compounds remaining in the oil after refining, such as sulfonates, petroleum acids, and even asphaltic bodies, may help to stabilize emulsions. Well refined oils of low viscosity  will  have  the  least  tendency  to  from  permanent  emulsions  with  water.

High interfacial tension will tend to cause emulsions to break. Many oil field emulsions are broken by causing the emulsion to revert from water in oil type to oil in water type. However, the best solution for this type of trouble is to choose oil additive combinations which do not promote emulsification.

Corrosive wear

Corrosive   wear  in  the  presence of a gear  lubricant may  be  due to the  environment if air, water , or electrolytes  are  present. If gear cases are not tight and high humidity prevails, rusting may occur, not only on idle gears above the oil line, but also on the walls of the gear case. If necessary, rust preventive compounds can be added to gear oils to counteract the action of moisture. Such additives may be polar compounds, often containing long chains, which will be adsorbed at the metal oil interface to form hydrophobic films. Prevention of corrosion due to electrolytes may be more difficult than prevention of rusting. However, if the contaminant is salt, the same types of additives as mentioned above will aid in corrosion prevention. If water soluble acids entering the gear case cannot be prevented, ordinary gear oils will not serve to prevent corrosion. In this case it may be necessary to use gears of different composition. Stainless steel will resist most acids and some electrolytes. High silica irons, while somewhat brittle, also have this faculty.

The corrosive wear most apt to occur in gear operations is that due to chemical additives, known as EP agents. The secret of a satisfactory EP gear oil is to obtain controlled  corrosion so that welding  of  the  metal  surfaces  will not take place  and  yet  asperities will  be  reduced. In  the  case of most EP gear oil  compositions  corrosive  wear  should  not  be excessive and  is actually  beneficial in  that it extends the life of the gears under extreme operating  conditions