The new N.E.P. roller chain from Tsubaki employs a metal coating process that allows a carbon steel chain to be used in wet conditions without corroding. The multi-layer metal coating process is modified for different components of the chain, balancing corrosion protection with wear resistance. An additional stand-out feature of N.E.P. chain is that its manufacturing process and component materials comply with new RoHS guidelines on restricting the use of hazardous substances.
Most ‘wet’ applications for drive chain involve some exposure to atmospheric moisture and / or intermittent exposure to water based applications. Completely waterproof chain is not suitable for these applications, as it is generally manufactured using a combination of stainless steel or engineered plastics. The drawback of these materials is that they are not as strong as carbon steel chain, and have to be oversized for high-load applications - in the case of pure stainless steel chain, it doesn’t perform well without immersive lubrication either. A corrosion-resistant chain based on carbon steel chain is therefore more desirable, as it can operate with standard power transmission components and sizing calculations.
Various coating methods have been used to protect the surface of carbon steel chain from corrosion when used in an environment where moisture is present, (typically outdoors or in a wet process application). The problem with this in the past has been that some surface coatings are extremely hard, such a chromium, and tend to peel-off due to surface pressure exerted by drive sprockets, or galvanisation, which is softer and wears away quickly as the chain articulates; thus leaving critical components open to corrosion.
Tsubaki N.E.P chain, however, uses a combination of three layers of surface coating, combining a highly resistant base layer that bonds a harder wear-resistant coating onto the chain bushes where they come into contact with sprocket teeth. An additional tough external coating is then used to cover and seal all the other component surfaces with further corrosion protection.
The combination makes for stunning results; in a salt water immersion test Tsubaki N.E.P. chain survived over 300 hours immersion without any sign of corrosion at all. This is compared to a standard carbon steel chain that would corrode to the point of being useless within just 24 hours. Samples that have been tested for up to 1500 hours have shown only slight surface discolouration, in what is one of the most destructive corrosion resistance test environments for ferrous engineering steels. (To put this achievement in context, check how much corrosion your car brake disks show after being left a couple of days with rain water on them).