GREASES
Make your switch to calcium sulphonate grease a success
Chris Pether, Industrial CTS Group Leader, Afton Chemical Ltd
Many lithium-based grease users will already be aware of compelling cost and performance reasons for switching to calcium sulphonate (CS) grease in their applications. Not all CS greases are equal though: drawing on field trial experience, Afton Chemical explains the key success factors for a smooth transition and how the right partnerships can really pay off.
Coming on top of the electronics industry’s needs, the growing demand for electric vehicle batteries has driven significant increases in the cost of many rare metals. Over the past three years lithium hydroxide prices have more than quadrupled, leaving lithium- based grease no longer able to deliver its signature balance of affordability and performance.
With its price now competitive and more stable than lithium, the appeal of calcium sulphonate as a grease thickener has grown. CS greases generally perform better in applications that demand structural stability and effective lubrication, especially at high temperatures, under heavy or shock loading and in wet conditions.
Based on Afton’s experience, collaborations and discussions with original equipment manufacturer (OEM) partners and customers, three key factors should be considered for a smooth transition to the right CS grease: performance balance, compatibility and longevity.
Rebalancing performance Each type of thickener contributes a different pattern of strengths to the finished grease, shaping vital properties such as structural stability, thermal management, load-carrying capability and water resistance. Calcium sulphonate thickener delivers inherently good performance in all these areas, benefitting grease manufacturers as the cost of performance additives can therefore be dramatically lowered, or even eliminated. Not all CS greases are interchangeable, though.
Traditionally, CS greases contain a higher percentage
of thickener than lithium-based greases. In applications such as automotive wheel bearings, this can cause the grease to harden over time. Fortunately, there is now an innovative CS grease production process that allows the thickener content (and with it, the risk of hardening) to be minimised – saving manufacturing time and cost, while still demonstrating proven all-round performance.
Ensuring compatibility When switching grease types, being able to remove all traces of the previous grease with a full strip down and cleaning with solvent is a rare luxury. More often, the new grease is simply used to physically displace the old. This creates a chance that they could interact negatively.
You might consult a grease compatibility chart before switching. Although, as Chuck Coe of Grease Technology Solutions LLC pointed out in his 2019 paper Compatibility Charts are Dangerous, these charts do not always agree. What’s more, they only account for interactions between different thickeners; there is no consideration of base oil and/ or performance-additive interactions. Incompatibility between any of these chemistries can weaken the thickener structure, resulting in poorer quality or inadequate lubrication. The most reliable way to confirm compatibility is to blend the new and existing greases, then test the performance of the mixture.
Afton typically carries out testing on 90-10, 50-50 and 10-90 mixtures of old and new grease to ensure there are no surprises. ASTM D6158 ‘Evaluating Compatibility of Binary Mixtures of Lubricating Greases’ Continued on page 15
LUBE MAGAZINE NO.174 APRIL 2023 13
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