
Grease is a thicker product than oil, which sees practical use as a lubricant.
Grease lubricant usually consists of a synthetic or petroleum-based oil, which is made more viscous by the inclusion of a dedicated thickening agent.
Semi-solid grease lubricants also contain specific additives that help it answer specific applications. Additives are usually designed to either exaggerate or suppress properties found in the grease’s base oil.
In this in-depth guide, we’ll take a deep dive into grease lubricants looking at their composition, applications, types available, buying considerations and more. Read on to update your understanding of these versatile lubricants.
Grease lubricant composition
The typical composition of grease includes around 80 to 95 per cent base oil and between five to 20 per cent thickener, with the additive package making up anywhere between 0 to 10 per cent of the product.
The ingredients of grease each have their own role to play. Thickeners are typically soaps and help the lubrication process, which reduces friction occurring between the metal surfaces of moving parts.
The thickening agent holds the oil in a semi solid state until it’s required to lubricate. Once exposed to temperature change, movement or vibration, the oil in the grease is released to perform its role.
The additive package complements the base oil’s ability to lubricate and enhances its capacity to protect against threats like rust and wear.
Greases have a high viscosity when applied, but when shear and stress is incurred, their thickness levels are reduced and they become more liquid, often having almost the same viscosity as the base oil. This process is known as thixotropy, which is a specific characteristic of grease lubricants that separates them from other products like petroleum jelly.
Grease lubricant application
Grease lubricants are used to defend mechanical equipment and components from water ingress and protect against rust (iron oxide). Greases also reduce friction encountered during mechanical operations.
These built-for-purpose lubricants are a high viscosity, making them a better option for applications when a liquid lubricant like an oil can’t stay in position. For this reason, oil and grease are not always interchangeable solutions.
Grease lubricants can act as an effective sealant, thanks to its excellent water resistance. It sees common use in the automotive sector for lubricating and protecting gears, wheel bearing and vehicle chassis.
When machinery is only used intermittently, like seasonal farming equipment, and remains in storage for extended periods, grease lubricants are applied to protect them during downtime.
Greases are also used with equipment and machinery operated under shock loads and higher pressures and temperatures, as it provides a cushioning film that is far thicker than an oil film. Additives in grease formulas can widen their temperature range or help them cope with extreme pressure and loads.
Quality grease lubricants can also help when machine parts are hard to access. With frequent lubrication impossible, greases are a more effective solution, as they can serve components for longer. As a result, they are often applied via a grease gun to “sealed-for-life” equipment, like vehicle gearboxes and electrical motors.
When components become worn, a grease lubricant can help. It can create and maintain a thick films over clearances that have been worsened by wear, and can often extend the service life of worn components that were oil lubricated previously. Thick grease lubricant films are also deployed to act as insulation against noise.
Grease lubricant types
A wide range of grease lubricants are available to order that have their own unique advantages.
Synthetic-based grease lubricants see frequent use with bearings and other rotating machinery components. They are highly tolerant to extreme operating environments and temperatures, considered too hostile for alternatives with mineral oil base. They are considered the best type of grease to resist oxidation.
Mineral oil-based grease lubricants provide high levels of mechanical stability and have good anti-corrosion attributes. This grease type is suited for automotive industry applications, water pumps and electric motors, and is often selected for its affordability.
Multi-purpose grease lubricants are a mainstay of the automotive sector.
Greases usually made using calcium sulphonate offer high resistance to water. These lubricants are not engineered for use in environments experiencing high heat levels.
Aluminium grease lubricants supply high temperature tolerance, good shear stability and outstanding resistance to water ingress. They are often used in food production machinery and can be applied on a full range of fastenings and components.
Lithium grease is described as a white grease for general purpose. Common applications include home and garden use like bearings and the hinges of doors and gates. This versatile grease has high viscosity levels and can work effectively under pressure for extended periods. It features a higher melting point than greases with a calcium base, and is suited to metal-on-metal applications. However, lithium greases are not water resistant.
Dielectric grease lubricants have a silicone base. They are provided in a milky white paste and are specifically designed for use with the most sensitive types of components found in the electronics industry. It can be extremely effective at protecting parts against galvanic corrosion that impacts high-voltage components.
Marine grease lubricants are especially designed for use with boats and their trailers and are designed to protect against extreme water exposure. Salt and freshwater impact conventional grease, but marine options can cope with both. It’s worth noting that marine grease is not compatible with lithium greases.
Key considerations when purchasing grease lubricants
Before buying a grease lubricant for a specific application or task, there are some important considerations users should pay attention to. These include viscosity, additives, base oil, shear stability, water resistance and consistency.
Grease lubricants must have a high viscosity index to remain in place and protect against friction and its unwanted impacts. For example, a thinner lubricant like oil can’t cope with heavy loads when parts are moving slowly, while a thicker lubricant added to a high-speed electric motor can’t provide adequate protection. Selecting a product with the viscosity you require is essential.
Different greases contain specific additives that enhance its attributes and help it perform better in certain applications. Study the additives included in a product and match them to your requirements.
Base oils are either synthetic or a petroleum derivative and have a different effect. Synthetic greases provide premier protection from oxidation and are deemed most resilient in every kind of weather conditions.
Grease lubricant consistency is affected by shearing, and its ability to retain its form in such circumstance is called its shear stability. Water resistance is also an important factor when you select a grease to protect against ingress or hold up when water contamination is likely.
The consistency of grease lubricants refers to how well it resists change when force is applied. Grease consistency is determined by the thickener included and its percentage, as well as the base oil’s viscosity.
Penetration is the measurement of consistency, and it depends on how the consistency is altered through working, handling or stress.
How does grease lubricant mitigate friction?
Friction is defined as resistance encountered as one object or its surface moves against another, restricting them from rolling or sliding over each other. Unlubricated surfaces are slowed by friction and can even become damaged due to wear and excessive heat.
While the surfaces of metal components appear smooth and even at a distance, under the microscope, they ae revealed to be rough. Imperfection in the metal called asperities jut out from surfaces and connect with one another causing drag, wasting energy and wearing out parts prematurely.
Grease lubricants control this friction and the harm it causes by creating a film that reduces friction between the moving surfaces. First, the grease cushions and smooths any bumps occurring between the moving surfaces and, as it is also liquid, it can change form and flow to provide further lubrication.
Finally, when selecting a grease lubricant, always consider the product recommended by your equipment manufacturer.