What is one reason emulsion formation in lubrication systems is undesirable?

Emulsion formation in lubrication systems is generally undesirable primarily because it promotes corrosion. When emulsions form, they comprise both water and oil, leading to a heterogeneous mixture. Water is known to cause corrosion in metallic components, as it can facilitate the oxidation of metals. This poses a risk to the integrity and longevity of the lubricated components, potentially leading to failure or increased maintenance needs.

In contrast, while increasing viscosity and reducing oxidation resistance can be concerns associated with emulsions, these effects are secondary to the primary issue of corrosion. The presence of water in the lubrication system can adversely affect the lubricant's performance, notably leading to wear and tear on the machinery. Furthermore, while thermal stability may not benefit from emulsion formation, the other choices highlight effects that, though relevant, are not as critical as corrosion in terms of system failure and maintenance.