Frequently Asked Questions
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What materials can be treated by the PCT process?
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How does PCT differ from microarc oxidation or plasma electrolytic oxidation?
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How does the PCT coating withstand mechanical impact?
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How does the PCT coating withstand mechanical deformations?
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How does the PCT coating adhere to sharp edges and corners?
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How does the PCT coating protect against high temperatures?
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What surface finishes can be achieved?
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How about chemical resistance?
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Can internal surfaces be treated with the PCT coating?
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Is it possible to mask parts so certain surfaces are not exposed to the PCT treatment?
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What types of coatings and secondary processes are available?
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How does the thickness of the PCT layer influence the final dimensions of the part?
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What is the color of the coating?
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What friction coefficient is achievable?
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What surface finishes can be achieved?
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How well does the PCT layer insulate current?
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What is the largest part that can be treated?
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Is PCT environmental friendly?
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What is the temperature of the electrolytic bath during the process?
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What is the difference between PCT treatment and hard anodizing?
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How do the costs of the PCT process compare to those of anodizing?
Q. What materials can be treated by the PCT process?
A. The PCT process can be applied to aluminium, magnesium, titanium and most of their
alloys.
Q. How does PCT differ from microarc oxidation or plasma electrolytic oxidation?
A. PCT scientists have improved significantly on these technologies with unique process
methods. PCT saves money by utilizing far less energy than the previous state-of-the-art of
microarc oxidation technology. PCT baths are totally "green", free of contaminants and
pollutants, and never require disposal. Proprietary secondary processes enable a wider
range of protection properties and solutions.
Q. How does the PCT coating withstand mechanical impact?
A. The PCT layer is hard and strong and atomically bonded to the substrate material. The
functional hard, ceramic layer protects against corrosion and wear. The ceramic consists of
hard crystalline phases imbedded in a matrix of softer oxide phases. This unique structure
gives the PCT layer a combination of high hardness and wear resistance. For example,
PCT effective protects magnesium bicycle frames that experience many types of impact
forces.
Q. How does the PCT coating withstand mechanical deformations?
A. Unlike externally applied coatings, the PCT process transforms the outer surface of the
substrate into a highly protective integral ceramic material. The PCT layer grows both above
and below the surface, forming a strong atomic bond between the metal substrate and
ceramic layer. Its amorphic character and fine scale of porosity gives it a degree of
compliance and stress resistance that will not crack or peel when subjected to moderate
mechanical deformation. For example, PCT-treated aluminum screws experience tension
and elongation with excellent results.
Q. How does the PCT coating adhere to sharp edges and corners?
A. The PCT treatment is a surface conversion process, differing from coatings formed by
deposits of external chemical elements. The PCT layer "grows" from within, maintains a
highly uniform thickness and fuses to the substrate in a tight atomic bond, with unmatched
adhesion, even on corners and edges. Thus, the PCT layer is not subject to surface tension
dynamics and is less prone to cracking on corners than hard anodizing.
Q. How does the PCT coating protect against high temperatures?
A. As an insulator, the ceramic is capable of withstanding temperatures as high as 2000°C.
However, the layer is very thin (normally between 10 and 50 microns), so the component's
resistance to extended high temperatures is limited by the properties of the substrate
material. For example, aluminum typically can withstand exposure to temperatures of 300350⁰C without affecting its mechanical strength. The dense nanoscale microstructure of the
PCT layer provides excellent protection to the substrate against short, high temperature heat
flashes, without being affected.
Q. What surface finishes can be achieved?
A. The PCT layer has a silky, matt texture. Secondary processes enable unique porosity
and roughness to be achieved. For example, paint and other materials such as low-friction
lubricants can be easily applied.
Q. How about chemical resistance?
A. The PCT ceramic layer is inert to most chemicals and corrosive conditions. In most
applications, the PCT layer provides excellent resistance to chemical corrosion. For
environments of exceptionally harsh chemicals, pores of main layer are sealed in a
secondary process to assure maximum resistance. In a salt spray test cell, unsealed PCTcoated aluminium exceeded 2000 hours, a significant improvement over electroless nickel
and sealed hard anodizing. After secondary treatment, the component withstood 10%
concentration of sulphamic acid at 40°C for 48 hours, and resisted H2SO4 at 95°C for more
than 10 days.
Q. Can internal surfaces be treated with the PCT coating?
A. Yes. PCT is an immersion process, so coating complex shapes and even internal
surfaces of cavities is possible – a clear advantage over processes such as plasma spray.
Every surface to be coated is considered when designing tooling and fixturing. Very small
and complicated spaces are more challenging than larger, well exposed surfaces but PCT
treats parts of many different geometries.
Q. Is it possible to mask parts so certain surfaces are not exposed to the PCT
treatment?
A. Yes, areas to be protected from the coating are masked prior to the treatment. In one
electronics application, electrical contact points are masked. In another case, selected
surfaced are dipped in the electrolytic bath.
Q. What types of coatings and secondary processes are available?
A. The PCT layer is generally recognized for high hardness, wear and corrosion resistance
and erosion protection. When required, a proprietary secondary process may be required
where the application calls for features such as: superior resistance to harsh acids, reduced
or enhanced friction coefficient, colors and special finishes, special dielectric and
conductivity attributes, heat protection, anti-fouling, anti-bacterial, and anti-galling. The
porous nature of the outer PCT layer is an excellent base for adhesives and other materials
such as polymers and Kevlar.
Q. How does the thickness of the PCT layer influence the final dimensions of the
part?
A. The thickness of the PCT layer typically ranges between 10 and 50 microns. Part of the
layer penetrates into the substrate and part of it grows outward in a closely controlled
manner. For applications with extremely tight tolerances, PCT's engineers work closely with
the customer's product designer to build in the necessary dimensional allowances.
Q. What is the color of the coating?
A. The PCT natural coating color ranges between grey and beige. A black coating can also
be provided. The slightly porous surface provides an excellent base for primers, metal
coatings, lacquers and paints.
Q. What friction coefficient is achievable?
A. The friction coefficient of a typical PCT layer to steel without secondary treatment is
about 0.3. By adjusting the PCT process parameters and applying a secondary process, a
wide range of friction values can be achieved. For example, low-friction lubricants and
materials such as PTFE lubricant are applied in a secondary operation. PCT treatment
helps eliminate high friction and galling typically associated with magnesium.
Q. What surface finishes can be achieved?
A. The PCT layer typically has a silky, matt texture with a surface finish of approximately
10% of the thickness of the applied layer. This very fine-scale pore structure is ideal for
retaining lubricants such as PTFE, producing a tough, non-stick or low-friction surface, or for
impregnation with paints. Unique porosity and roughness requirements are achieved in a
secondary process.For example, epoxy paint applied to PCT-protected magnesium bicycle
frames results in an impact-resistant and good-looking shiny finish.
Q. How well does the PCT layer insulate current?
A. As a ceramic, the PCT is an excellent insulator, finding use in applications where
galvanic erosion is apparent. If required, it can be given conductive properties where are
Faraday Cage effect is required
Q. What is the largest part that can be treated?
A. In theory, there is no limit to the size of a part to be treated. In practice, the size of the
reactor bath and electric supply are determining factors along with economic considerations.
For example, PCT currently processes parts ranging in size from aluminum fasteners to
tubes 6 meters in length.
Q. Is PCT environmental friendly?
A. The PCT process is very friendly to the environment. It uses only mild, natural elements
– no heavy metals, ammonia, pollutants, acids, or waste. Compared to anodizing, PCT
requires fewer process tanks, does not employ acids, and does not create harmful fumes
and other pollutants which require treatment and special handling and safety precautions.
The PCT bath never requires disposal.
Q. What is the temperature of the electrolytic bath during the process?
A. Both the bath and treated component are maintained at a temperature of 20-30°C.
Q. What is the difference between PCT treatment and hard anodizing?
A. The PCT process resembles anodizing in that electricity is passed through an electrolytic
bath, but the technology is significantly different and produces very different results.
Compared with hard anodize, PCT offers superior resistance to corrosion and erosion
qualities. Additional treatments provide increased resistance to aggressive materials, very
active acids, and erosive environments. The treatment on aluminum is up to four times more
wear resistant and far less prone to cracking on corners.
Q. How do the costs of the PCT process compare to those of anodizing?
A. Anodizing is one of the most popular techniques employed to improve the corrosion
resistance of light metals. In conventional applications, PCT is not meant to compete with,
or replace anodizing. However, the PCT process is able to produce ceramic coatings with
higher performance and provides technical solutions where anodizing fails. The comparison
of the two protection methods must be made on a case-by-case basis, taking into
consideration many factors including substrate material, geometry, protection and
operational life requirements, and environmental restrictions.
Operationally, the PCT process does not generate sulfuric acid fumes as in anodizing,
eliminating the need for venting and scrubbing equipment, and the purchase and disposal of
filters. The process involves fewer stages. Typically, only two or three baths are used
instead of 8 in the anodize process. In hard coat anodizing, larger chillers are required to
control electrolytic bath temperatures. Hard coat anodizing uses low DC voltages for
extended periods, while the PCT process uses high AC voltages for shorter durations.