There are two major classes of protectives, depending upon the application on the aircraft :

1. For internal preservation of engine/hydraulic system
2. For external airframe applications

For preservation of piston engines, oils are used for preventing the cold corrosion that can occur during storage or shipment due to the trapped products resulting from the combustion of leaded fuel. The methods employed  include :

1. Using a storage oil in the engine oil system, followed by spraying the various parts internally with a wax thickened oil / fuel composition.
2. Using a combined operational cum storage oil to obviate the necessity of depreservation, when putting the engine back in service.

In case of turbine engines, the oils used can be mineral type of low viscosity or corrosion inhibited versions of the synthetic engine oil in use. Similarly, preservative versions of hydraulic fluids are used for the system during storage.

In a unique system adopted in Russia, a standard corrosion inhibitor additive is added to the system oil prior to storage and this product is recommended for internal combustion engines, turbines engines as well as other equipment.

For external protection, the choice of the product to be used depends upon the degree of protection required and the expected ease of removal. Accordingly the range comprises of :

• Non-drying oily film protectives.
• Solvent-deposited protectives, forming coatings of various types and thickness, ranging in consistency from soft to hard. Certain grades also possess dewatering properties.
• Hot-dip protectives forming grease-like films of soft or medium consistency.
• Preservative oils specially designed for the internal protection of engines and certain machines during storage,
• shipment or periods of laying-up.
• Pastes / Compounds.
• Wax based and hard film type for protection during extended storage.