Cochin laboratory

SILVER STRIP CORROSION (IP 227)

Corrosiveness toward silver is becoming increasingly important, and a test method has been developed that is closely similar to the copper corrosion test. Even though DEFSTAN is not recommending the silver strip corrosion test , for CEMILAC type approval it is included in our specification.

TRACE METALS

(Trace metals such as iron, nickel, vanadium, calcium, titanium, magnesium, sodium, cobalt, copper, tin, and zinc occur in crude oils. Vanadium and nickel are bound in organic complexes)

When fuels are combusted, metals present in the fuels can form low forming compounds corrosive to metal parts. Trace metals present in petroleum can deactivate catalysts during processing. Trace metals in turbine fuels can cause corrosion and deposition on turbine components at elevated temperatures. Some diesel fuels have specification limit requirements for trace metals to guard against engine deposits. In addition to the naturally occurring metals in the crude oil and the petroleum products derived from it, certain metals are added as additives to lubricating oils and similar products. These metal additives act as detergents, antioxidants, antiwear agents, etc. In used lubricating oils, several other metals may be present coming from the engine wear in addition to those from the additives. On the other hand, in certain petroleum products even trace amounts of metals may prove deleterious to engine performance. Hence, it is important to have test methods that can determine metals, both at trace levels and at major concentrations. These metals are quantitatively estimated (ppm, ppb or ppt level) by different instruments via different techniques.XRF, Flame AAS, ICP-AAS, ICP-MS, ICP-AES are some of the tools used.
VAPOUR PRESSURE

Vapor pressure is an important physical property of liquid spark-ignition engine fuels. It provides an indication of how a fuel will perform under different operating conditions, such as whether it will cause vapor lock at high ambient temperature or at high altitude, or will provide easy starting at low ambient temperature. Petroleum product specifications generally include vapor pressure limits to ensure products of suitable volatility performance. Vapor pressure of fuels is regulated by various government agencies. Vapor pressure of crude oil at various vapor-liquid ratios is also an important physical property for shipping and storage.