PEEK Corrosion Resistant Coating? Here's A 'PEEK' At This New Engineered Thermplastic

PEEK corrosion resistant coating, you say? What's PEEK? This comparatively new engineered family of thermoplastics: PEEK (polyether etherketone), PEK (polyether ketone), and PAEK (polyaryl etherketone) are partially crystalline engineering thermoplastics (plastic polymers) that can be used at high temperatures. These resins have excellent chemical resistance. Their high thermal stability comes from rigid ketone and phenyl groups, while their high strength and thermoplastic state below the decomposition temperatures come from the ether groups.

These compounds can have melting temperatures in excess of 650 degrees Fahrenheit, with mechanical properties retained to about 500 degrees Fahrenheit.

Tensile properties are comparable to most engineering thermoplastics. Creep resistance is outstanding and may sustain large stresses over a useful service life without measurable strain.

Wear rates and friction are becoming increasingly important against metals. Corrosion protection, too, is often an integral part. For these reasons, PEEK (and related polymers) are becoming increasingly important, as demands on them for their structural properties grow, particularly at elevated temperature.

Friction from composites of thermoplastic vary in a unique way from metals in that their asperities (surface irregularity) will deform much more under load. Consequently, friction between a thermoplastic and metal surface is typically characterized by adhesion deformation disproportionally lower to load. The primary mechanism is adhesive wear, which is characterized by fine particles of polymer removed from the surface. This is a good illustration that the surfaces are wearing properly. (Large gouges or corrugations in a polymer surface would suggest not adhesion wear, but abrasion wear or the material's pressure velocity limit was violated.

Wear factors of PEEK plastics, PEK or PAEK appear much less affected by load and speed components, independent of PV. Wear performance seems to be better at low pressures and high speeds, rather than high pressures and intermediate speeds. All display excellent resistance to wear over wide ranges of pressure, velocity, temperature, and counterface roughness.

Properties of some of the PEEK coating or PEEK plastic plastic are now characteristic of PTFE, PFA, and other corrosion resistant compounds. The advantage is in markets demanding greater resistance to abrasion, higher temperature environments, too. Next time consider PEEK corrosion resistant coating.

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Thermal Spray - Here's A Second Look

Sure, hard facing relates to thermal spray, though it's really more about depositing 'filler' materials onto a metal surface for repair or dimensional restoration. And, normally, these improvements relate to promoting wear resistance, alone.

But did you know these 'overlays' of material may also contribute to corrosion prevention, low friction, anti-fretting or galling, even release (non stick) properties? What was formerly developed for rebuilding worn parts or those with machining errors is now extending into many fields of surface engineering.

The principle of applying thermal spray is quite basic. That is, molten or semi-molten metals, alloys, or ceramics, atomized, are fed toward the work piece by a jet stream of air.

As these particles impinge the working surface, they dissipate their heat, quickly cooling, building up, fusing into a cast-like structure described as highly cohesive. Resultant surface finishes, as-sprayed, typically range between 100 and 400 micro inch. So, depending on requirements, finish grinding or polishing may be required. (Values under 10 micro inch are very much attainable.)

What types of materials can be applied by thermal spray? The answer is most metals, ceramic, cermet(ceramic-metal combinations), tungsten carbide, even organic-based compounds like polyesters.

Adhesion, largely mechanical (versus metallurgical), is excellent. Grit blast, as a means of surface preparation, is typical to best promote adhesion. Though tensile strength can be sometimes improved upon with higher temperature processes, depending on choice of material, through micro-welding or diffusion.

Common methods of application include HVOF (high velocity oxygen flame), which is similar to the combustion powder thermal spray process (LVOF), though with increased density, stronger bonds and lower residual tensile stress. Plasma spray and vacuum arc spray are also popular.

Applications continue to grow with this technology. Food processing, packaging, molding, plastics, paper and chemical processing, are just some of the newer, relevant applications. (Many materials are regarded non-objectionable with FDA.)

Ideally, look for thermal spraying processes with minimal heat transfer to your work piece. Just to be certain your surfaces are free of warping, surface distortion. Latest versions include 'higher kinetic energy systems' to ensure highest density, particle-to-particle cohesive bonding. The result is long-lasting, cost-effective, surface performance.

Want to create a new dimension to your surface? Take a second look at Thermal Spray!

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