Sulfated Residue, Lead, Iron and Copper in Lubricating Oils

In this  methods, the sample  is completely  oxidized  by wet  ashing  with  concentrated  sulfuric acid, concentrated  nitric  acid and  hydrogen  peroxide, or  if  only iron and copper  are  to be  determined, by dry  ashing. To determine sulfated  residue, the  solution obtained by  wet  ashing  is  transferred  to a weighed  dish, evaporated  to  dryness, ignited at 775 degree C, cooled and  weighed. In determining lead, iron and  copper, the  solution resulting  from  the  wet  ashing is  mixed with  alcohol and  filtered  to give  a  precipitate  of  primarily  and  sulfate. This  precipitate  is  boiled  with  sodium carbonate and  then  precipitated  with  hydrogen  sulfide.

Iron  and  copper are  determined on  separate  aliquots  of the  filtrate  from  wet  ashing. The  iron is  separated  as the  hydroxide and  determined colorimetrically  as the  orange  ferrous  orthophenanthroline  complex,  while  copper  is  determined  colorimetrically  as the  yellow diethyldithiocarbamate  complex

Gear Materials of the Future

The lubricants required in the future  for gear  service  will  probably be  tailored to the  mating  surfaces which are to  be  protected  against wear. Not only will improved ferrous alloys and other metals be used, but also there will be more nonmetallic gears in service. Whether these will be primarily plastic gears or simply improvements on such forms as laminated gears remain to be seen. Probably plastic gear use will increase, particularly in small mechanisms and where loads are light and there is no wide temperature variation.

Investigations are being made  to determine what  combinations of  mating  gears will  show  the  least  wear  when  no  lubricant is provided. This is a fertile field and the supplier of lubricants should keep advised of the advances.

Nonferrous Gears and Their Lubrication

While the tendency is to think only of gears made of ferrous metals, we find in Dudley^16 the statement: “A wide variety of bronzes, aluminum alloys, zinc alloys, and nonmetallic plastics and laminates are used to make gears.”

Fortunately, well refined mineral oils have little action on most of the combinations. We say  combinations  because in  many  cases the nonferrous  gear is driven by a  steel pinion, but when the loads are light and the  gears are small, both members  may be of the nonferrous  material.

Nonreactive oils should be used with nonferrous gears unless specific recommendations state otherwise. This is illustrated in the case of worm gears where the gear is normally made of bronze. The  general  recommendation for  such units is a mineral  oil  containing  tallow, although  often  such  oils  contain  lead  soaps  and  occasionally certain EP agents.

Synthetic fluids, both diesters and “Ucon fluids, have been used as lubricants with nonferrous or ferrous and nonferrous combinations of gears. Where a problem of lubricating  an  unusual combination of  gear  materials is  encountered, the manufacturer of  the gear set should  be  able to  make a safe  recommendation. However, lacking a  suggestion, a well  refined  lubricating  oil  with no reactive additives  present  can  generally be used with safety in the  case of  nonferrous  gear sets.

Minimum action of gear oils on components of mechanisms

Well refined mineral lubricating oils have little if any action on most metals, particularly ferrous metals. It is only upon prolonged use at elevated temperatures that such oils may from compounds which will act upon metals. Since such oil changes can be retarded or almost completely arrested by the use of oxidation inhibitors and also metal deactivators or pacifiers can be included, there should be little concern about the action of straight mineral oils upon the metal components with which they come in contact.

What we are concerned with here is the action on parts made from other materials, such as paper, plastics, rubber, etc. Seals are likely to be made from rubber, either artificial or natural, and any deterioration of the compositions due to the lubricant should be at a minimum. Many seals consist of compounded materials, such as “neoprene,” and it is found that oils high in aniline points, as are most high V.I. oils, will have little effect on this compound.

Automatic transmission mechanisms may be found to contain paper and “Nylon” parts. In future devices which will require transmission fluids, a greater variety of components may be used. The safest course when supplying oils for contact with unusual materials is to have the fluids pretested to determine their suitability.