The future of metallization

Oct 28, 2019

The Yankee cylinder is the heart of a tissue machine and its surface is critical to production output and creping quality. Unfortunately, constant exposure to chemicals, wet tissue, internal steam pressure and high surface temperatures leads to surface wear and corrosion.

A worn Yankee cylinder surface will reduce production output and can have a detrimental impact on tissue quality. Metallization is a proven method for protecting, refurbishing and prolonging the lifetime of the cylinder surface. But metallization is not perfect. Thankfully, new surfaces have been developed which now are safer for people and the environment.

Yankee cylinder reconditioning

Metallization – thermal spraying – is a well-proven method for applying a metallic, homogenous, hard-facing surface onto a Yankee cylinder. Besides improved creping, metallization will extend cylinder lifespan.

Metallization of cast iron cylinders is increasingly common, albeit optional. On these, metallizing decreases surface and/or heat-transfer defects, increasing durability and decelerating wear on cylinders. On the contrary, steel cylinders must undergo metallization before their use, hardening their soft surfaces.

Once a means of preservation, paper manufacturers now use metallization as a reconditioning method – after grinding – for maintaining production levels and avoiding expensive equipment replacement.

A chrome-free alternative

Unfortunately, metallization comes with associated health, safety and environmental risks. The method produces hexavalent chromium – a harmful component of most iron-based, hard-facing alloys.

To improve worker safety during thermal spraying, as well as sustainability of the coating to comply with potential future legislation both in the EU and the US, a chrome-free Yankee cylinder coating has been developed.

By collaborating with tissue industry experts, several new alloys now exist with optimized microstructures that achieve targeted performance metrics, such as a stable creping surface.

All the benefits, none of the disadvantages

The new thermal spray coatings deliver numerous advantages over previous benchmarks.

Whilst 100% chrome free, they have been tailormade for the tissue industry to increase wear resistance, further extending cylinder service life. The uniform surfaces created are also ideal for running ceramic doctor blades and providing better sheet adhesion during tissue production.

For more information on this new coating, view this film

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