Moisture Corrosion Characteristics of Universal Gear Lubricants

A full  scale axle  gear  unit is used  for this test. Before the test , the  parts  are cleaned as follows: immerse   in a 1 per cent solution of Sodium Hydroxide  for  1 hour. Rinse  the  parts with water  until free  of caustic. Dry  the parts  by  rinsing  with  methanol, followed by  air-blowing to  remove  the  methanol. After  the assembly, 28 ml of  distilled  water  is put in the axle housing followed by  filling with  the gear lubricant to the  level plug. The  propeller  shaft is  rotated  at a speed of 2,400 rpm  for  4 hours while  the  oil  is maintained  at a temperature  of 180 degree F. At the  end of the  4 hour period, the  drive is stopped and  the  axle  test  unit  is placed on the  storage  rack  without  draining  the  lubricant. There  it  is allowed to remain for a  10 day period at room  temperature.

At the  end of the 10 day period, the lubricant is  drained and  the  axle  disassembled  for  inspection. The  rating  of the  lubricant shall  be based  upon  visual  inspection for  rusting  of the  gears, the  pinion-gear  bearing,  the  differential-carrier  bearings and  the  differential-gear  thrust surfaces.     

Emulsion Tendencies of Lubricating Oils

Federal Test Method 3021.5 is intended for use in the determination of the emulsifying tendencies of lubricating oils. The test  consists  of  placing  40 ml each  of the  test  oil  and  of  either  distilled  water or  a one  per cent  salt solution in  a 100 ml graduated cylinder.  The  cylinder  is  then  placed in  a  bath  regulated to  either 130 0r  180 degree F and  the  contents  stirred with  a paddle  at  1500 rpm  for  5  minutes. Following this, while  still  maintaining  the  cylinder at  the  test  temperature , the time  required for  the  emulsion to  break  is  noted.

In  the  case  of  circulating  oils where  the  lubricant may  become  contaminated with   water, a firm emulsion  would  interfere  with  both  circulation and  lubrication. Therefore, under such  conditions  of  operation,  oils  which  show  little  tendency  to  emulsify  are  desirable.