KMC EPT Anti-Rust Chain Review

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KMC claims that its Eco Proteq (EPT) coating makes chains super resilient to rust and dirt for the best performance in extreme conditions. Do EPT chains live up to these claims?

Before I dive into the specifics of the KMC EPT chains, lets have a brief review of why chains rust and what factors can prevent this. Almost all bicycle chains are currently made of steel. Steel is a good choice for a high wear component like a chain because of its strength and low cost. A weakness of steel is that it is susceptible to corrosion in the form of rusting when exposed to water and oxygen. Various plating and coatings protect steel from corrosion anywhere the material is used on a bicycle. These may take many forms with varying levels of durability including grease on steel bearings and paint on steel frames. Chain lube, similar to grease on bearings, both reduces friction and provides some corrosion protection to parts of the chain. Chains may also benefit from plating with layers of corrosion resistant metals of which nickel is currently common although chrome, titanium nitride, and others are also available.

KMC claims that the EPT coating is twice as effective at preventing rust as their previous best anti-rust coating (Rust Buster) and ten times as effective as a standard chain. KMC does not state the details of what exactly the EPT coating is. The previous Rust Buster coating was based on a zinc and chrome plating process. Unlike many chains where only specific components receive coatings, the EPT is applied to every surface including the outer plates, inner plates, pins, and rollers. While offering the best protection, this likely contributes to the higher cost of EPT chains. The EPT finish is available on single, 8, 9, 10, 11 and 12 speed chains for a premium price. For comparison, the KMC X9 chains are available in partial nickel plating, both inner and outer nickel plating, and EPT for retail prices of $25, $30, and $42 respectively.

I tested the KMC X9 9-speed EPT chain on my Roloff internal gear hub equipped bike. 9-speed chains are the recommended chain for this drivetrain and it has a straight chain line like single speed setups. I rode this bike in some of the toughest conditions including the Texas Coast Bikerafting Route (TCBR). The trip was punctuated with severe storms including the bike being outside in >30 mph winds with 3 inches of rain falling in a couple of hours. Beach conditions were poor many days including multiple days of double high tide where little dry beach was available for riding, resulting in salt water and sand spray regularly onto the drivetrain. I also flipped my raft once with the bike attached which resulted in a complete dunking in the ocean. Days would go by without fresh water to rinse the drivetrain, but it was cleaned a few times with dish soap and an old toothbrush during the trip. The chain was ridden for the first few hundred miles with the factory lubrication, and then I used Silca Synergetic wet lube. It’s a good long lasting lube specifically for harsh, wet riding. During the first part of the trip, the chain did remain rust free despite the harsh conditions. Later, some rust was apparent but appeared to be coming from the internal surfaces of the chain and not the exposed surfaces of the plates. This would be consistent with the eventual wearing through the plating material on the pins or the bushing like flanges of the inner plates (the areas wear chains normally wear, contributing to “chain stretch”). The chain had already exceeded 0.5% elongation upon returning and first checking chain elongation at 1,274 miles and it exceeded 0.75% elongation shortly after with a total of 1,390 miles over 32 days. This is shortest lifespan that I have ever observed for a chain on any of my bikes, and even though the conditions were extreme, it left me unimpressed.

KMC EPT Chain After TCBR
Chain after returning the last day from the extreme riding conditions on the TCBR.

There may be specific situations where the EPT treatment is beneficial. I would speculate that this type of treatment could be beneficial for those living near coastal environments where either the bike is ridden infrequently (thus the chain being exposed to salty coastal air over a long lifespan). Take that with a grain of salt as it’s just speculation. For those that ride in wet, muddy conditions, you should be cleaning, drying, and re-lubing your chain after rides in those conditions and that should be sufficient to prevent corrosion.

I will not be purchasing another EPT treated chain as it costs more and did not appear to offer any practical benefit with my usage. For the price of one KMC EPT X9 chain, I was able to buy two SRAM PC-971 chains that in previous usage provided longer lifespan even though they do not even have a full nickel plating. I think for the vast majority of riders, the EPT coating will not offer significant benefits over more common and cheaper nickel plated chains. The keys to getting long life and a rust free chain are regularly cleaning your chain and appropriate lubrication based on riding conditions.


  • 114 links
  • 1/2″ X 11/128″ – pin length: 6.6 mm. Compatible with all 9-speed.
  • Claimed Weight: 288 grams
  • 100% EPT coverage on outer plates, inner plates, pins, and rollers
  • Surpasses 650 hour salt spray test
  • MSRP: $42
  • Price Paid: $28.86
  • EPT coating also available on KMC single, 8, 10, 11, and 12 speed chains

Rowdy Fisherman

I enjoy combining adventure with cycling. Bikepacking, bikefishing, ultra distance, all road, former road, off road, and unusual locations. Riding the best and the worst roads. I hope that I can share these adventures with you and inspire others to take on their next adventure!

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