Penetrants and penetrating oils are low-viscosity fluids used to free rusted or corroded nuts, bolts, fasteners, shafts, pulleys, and other mechanical parts. Most penetrating fluids contain a low-viscosity solvent or volatile vehicle. Penetrants and penetrating oils that act as cleaners and surface conditioners also remove tar, chewing gum, adhesives, and rust. As their name suggests, these products penetrate the metal’s pores and deposit an oil-film (typically solvent-based) which displaces water and protects the metal from moisture.
There are several basic types of penetrants and penetrating oils. Straight oils are non-emulsifiable products that are used in machining operations in an undiluted form. They are composed of base mineral or petroleum oils and often contain polar lubricants such as fats, vegetable oils and esters, as well as extreme pressure (EP) additives such as chlorine, sulfur and phosphorus. Water-soluble and emulsion fluids have a high dilution or very low concentration and include high water content fluids (HWCF). Soluble oil fluids form an emulsion when mixed with water. These penetrants and penetrating oils are used in a diluted form with concentrations ranging from% to 10%.
Synthetic and semi-synthetic penetrants and penetrating oils are based on synthetic compounds such as silicone, polyglycol, esters, diesters, chlorofluorocarbons (CFCs) and mixtures of synthetic fluids and water. Typically, synthetic fluids have the highest fire resistance and cost. Micro-dispersants are penetrants and penetrating oils that contain a dispersion of solid lubricant particles such as polytetrafluoroethylene (PTFE), graphite, and molybdenum disulfide or boron nitride in a mineral, petroleum, or synthetic oil base. Penetrating fluids that are designated as HWCF fluids are also available.
Selecting penetrants and penetrating oils require an analysis of product specifications and features. Parameters include density or specific gravity, kinematic viscosity, viscosity index, pour point, flash point, operating or use temperature, boiling point, concentration (as used), thermal conductivity, and dielectric strength. With regard to features, some penetrants and penetrating oils are described as aerosols or sprays, anti-knock agents, corrosion inhibitors or rust preventatives, lubricants, biocides, and oxidation inhibitors. Others are listed as extreme pressure (EP) additives, low or non-foaming fluids, shock or vibration dampeners, sludge dispersants, or water displacement lubricants. Specialty penetrants and penetrating oils are also available.