Acid-neutralizing of marine cylinder lubricants: Effects of nonionic surfactants

The neutralization reaction between a concentrated sulfuric acid droplet an d a series of model marine cylinder lubricants (MCLs) formulated with an ov erbased sulfonate and a series of different nonionic surfactants was studie d using a capillary video-microscope technique at room temperature and a ph ase transfer neutralization rate test at several temperatures up to 55 degr ees C. The model MCLs were characterized using dynamic light scattering and transmission electron microscopy. On the basis of the observations, a mech anism is proposed fur the neutralization reaction which involves the initia l formation of a mixed reverse micelle system between the overbased sulfona te and the nonionic surfactant followed by the neutralization reaction at t he aqueous acid/oil interface to form calcium sulfate crystals. The rate of the neutralization reaction is enhanced by the presence of the nonionic su rfactants in the model MCLs and is consistent with the formation of the mix ed micelle systems which makes the basic core (CaCO3/Ca(OH)(2)) of the over based sulfonate more accessible to the aqueous acid due to the increased si ze and flexibility of the overbased sulfonate reverse micelle.