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Dual Coated Power Pistons

An upgrade set as the engineering standard for the protection of power pistons
for large bore compression and power generation engines.
Cooper Machinery Services Emerging Legends Series Logo

an environmentally friendly alternative to tin plating

As part of our Emerging Legends™ series of new products and services, Cooper is excited to introduce dual coated manganese phosphate and graphite technology as the engineering standard for the protection of power pistons for large bore compression and power generation engines.

Traditionally, many engine manufacturers and service providers have used electroplated tin on the surface of the piston skirts. The purpose of this coating is to reduce friction and allow for break-in of the piston to the liner surface. The environmental, health, and safety concern for tin plated coating is rendering the tinning process a less attractive option within gas compression and power generation industries. In addition, tin can cause a loss of clearance and hot spots on the piston. Accordingly, dual coating will replace the use of tin plating in its entirety within Cooper.

Manganese phosphate coating, along with graphite spraying, has been used on pistons for many years in marine and locomotive engine applications and has a successful track record as an alternative to tin plating. Cooper has accumulated thousands of operational hours with dual coated pistons on Cooper-Bessemer model GMV, V-275, W-330, and Quad integral engines, and dual coating is available on new pistons for all product models of Cooper-Bessemer slow speed integrals. The coating will become available for AJAX, Clark, Ingersoll Rand, and Worthington slow-speed integral engines by the end of 2021.

a robust & Durable dual coating

The piston has a dual coating consisting of a bottom layer of manganese phosphate and a top layer of graphite-based anti-friction coating. The combined thickness of the manganese phosphate and graphite is 0.0005″ to 0.0015”. Manganese phosphates’ natural crystal structure is very durable and does not flake. Due to its structure, it performs well for break-in between the piston and cylinder liner, and it provides continued wear protection after the break-in period. In addition, manganese phosphate increases corrosion resistance, thereby greatly improving the piston shelf life. The dual coating of manganese phosphate and graphite provides excellent strength and oil lubrication properties which helps to significantly reduce friction losses and scuffing of the cylinder bore.

Key Advantages of Dual Coating


Cooper’s new dual coated power pistons are an inaugural member of the Emerging Legends™ Series, our portfolio of new products and services that advance the industry and transform Cooper’s traditional way of doing business. Emerging Legends™ serves as a testament to the Cooper commitment of optimizing performance of legacy engines and compressors, helping our customers extend the life of their equipment, and bringing environmentally sustainable solutions to the market.

Comparison of dual coating & tin Plating for key parameters

Significant testing has been carried out on our new piston to compare the dual coating to tin plating for  component wear, scuffing, and scoring. Dual coating outperformed tin plating in each category.

Dual Coated Piston field experience

Cooper has tested the dual coated piston with eight (8) customers and has accumulated over 200,000 operating hours on numerous Cooper-Bessemer models without any issues. The following table shows the Cooper-Bessemer integral engine models which have been operating with the dual coated pistons.