HPM + CR
Multiuse Grease. Focusing On The New HPM + Corrosion Resistance Specification.
In this article we take a look at the corrosion resistance enhanced category of the new NLGI high-performance multiuse grease specification.
Multiuse greases are required in a variety of different applications, many having different performance challenges. In specific applications, the grease may need to deliver enhanced levels of performance over the high-performance multiuse (HPM) core specification, such as increased corrosion resistance (CR).
The HPM corrosion resistance enhanced category primarily addresses salt water and sea water applications where additional performance benefits over the HPM core specification are required, such as boat trailer wheel bearings for use in sea boat or private sea fishing applications.
Greases meeting the enhanced corrosion resistance specification requirements will be awarded the HPM + CR certification mark. In order to meet this higher level of performance, a grease must first pass the HPM core specification, discussed in an earlier article in the series (see link at the end of this article to learn more).
To demonstrate an enhanced level of corrosion resistance over the HPM core specification, there are an additional three test performance requirements.
The first test determines the corrosion-preventive properties of greases in dilute synthetic sea water environments (ASTM D5969). While similar to the bearing rust test contained in the HPM core specification (ASTM D1743), the key difference is the use of synthetic sea water as opposed to distilled water during the test procedure, as well as a shorter incubation period in the ASTM D5969 test.
The second and third performance requirements for the enhanced corrosion resistance category use the ASTM D6138 Emcor (anti-rust) test, which assesses the ability of grease to prevent corrosion in rolling bearings. While this test is already contained within the HPM core specification, rather than using distilled water in the test, the enhanced corrosion resistance category requires the separate testing of synthetic sea water and sodium chloride solution to ensure added anti-corrosive performance in sea water and salt water applications.
The HPM + CR enhanced category provides the opportunity to market higher performing multiuse greases for applications which require enhanced levels of corrosion resistance, above the HPM core specification.
In order to pass the more severe corrosion resistance specification requirements, the grease lubricant requires careful re-balancing of higher performing bespoke salt water rust inhibitors.
The availability of HPM certified greases provides a true upgrade in performance levels, delivering tangible benefits to all stakeholders in the supply chain.
HPM® is a registered trademark for NLGI. To learn more, visit www.NLGI.org.