Precious metals are used in the manufacturing of fuel tank level sensors because their resistance to corrosion by water, water soluble salts and acids in fuel systems extends the life of the sensor. However, they are not immune to the effects of elemental sulfur, hydrogen sulfide, and volatile mercaptans that often remain in fuel even after hydroprocessing.

These compounds are corrosive toward silver and silver-containing alloys present in fuel tank level sensors. Over time, by-products of silver corrosion accumulate on the level sensor contact points and prevent accurate measurement of the fuel volume in the tank. In severe cases, the fuel level gauge will continually indicate a full tank even as the fuel volume in the vehicle tank is being depleted, leaving the operator of the vehicle unaware of the actual fuel tank volume. This problem most frequently occurs in more volatile fuels such as gasoline.   
 
Nalco Water provides a silver corrosion inhibitor with dual functionality:

• Scavenges corrosive elemental sulfur present in fuel
• Protects silver from attack by other corrosive compounds such as hydrogen sulfide and mercaptans