Polar and protective properties of esters

1. A number of esters used as aviation oils and hydraulic fluids have been investigated with respect to polar and electron donor-acceptor properties at an interface with metal. It has been shown that the majority of the esters are high in dielectric permeability and that they decrease the electron work function of metals, being electron donors and being sorbed at the > CO = group. 2. The least polar of the esters is the pentaerythritol ester of C5–C9 acids, which increases the electron work function. The sorption of esters on metal is in the nature of a physical adsorption. Satisfactory protective properties and the capability for rapid removal of an electrolyte from a metal surface are provided by the esters of mmethylcyclohexanol, adipic acid, and 2-ethylhexanol (No. 7), the monodecyl ester of diphenic acid (No. 8), and the didecyl ester of benzylsuccinic acid (No. 9). 3. Esters can be utilized as components of combination corrosion inhibitors, but all of the esters that were investigated are inferior in this respect to fatty acids.