Colouring stainless steel

When planning, designing and executing high-quality projects in architecture and product design, the choice of an ever-increasing number of decision-makers falls on stainless steel as a material.

Stainless steel is an outstanding and excellent material due to its many advantages, its high functionality and long service life, its versatility and its unique visual and haptic appearance.

However, choosing stainless steel in no way means committing to just a grey, silver finish. There are a number of options and methods for adding colour to the material. We would like to introduce you to the possibilities of "colouring stainless steel" and "blackening stainless steel" here.

Can stainless steel be coloured?

We are often asked questions such as "Are there options for colouring stainless steel similar to anodised aluminium?", "Can stainless steel be coloured?", "Can stainless steel be blackened?" or "How do colour stainless steel?".

Other metals such as aluminium can be anodised, brass burnished, titanium anodised and black steel painted or powder coated. The latter two processes are in principle also possible with stainless steel, but they take away its visual liveliness and attractiveness. Therefore, an alternative method has to be found to solve the task of colouring the stainless steel.

mirrorINOX offers the customer, who has decided in favour of stainless steel and wants a coloured surface for his application, ideal solutions for stainless steel colouring from our own production, which meet the highest demands in terms of both function and appearance.

How does stainless steel colouring work?

We would like to explain the following chemical and physical colouring or colour coating processes in more detail:

Galvanic colouring of stainless steel

This chemical galvanic process, also known as the "INCO" process or the Polispectral and ColourTex process, uses sulphuric or chromic acids. Due to its poor environmental compatibility, it is no longer permitted in the EU and is only tolerated for a limited period with exceptional approval. In addition, colour variations, light-dark differences or even different, undesirable colours within individual sheets and within individual batches can occur in stainless steels whose surfaces have been coloured using this process in shades such as Charcoal, Bronze, Black, Rosy Gold, Cobalt Blue, Blu, Bronzo, Grigio, Nero, Oro, Rosso, Verde and Viola. Cases have also been reported where the colouring was not permanent, "washed out" or faded.

For these reasons, galvanic colouring of stainless steel is not a method mirrorINOX applies.

Taking into account sustainability, colour uniformity and reproducibility, functionality, visual quality and versatility, we at mirrorINOX have included and further developed the following physical processes of stainless steel colouring in our manufacturing programme:

PVD/TiN coating process

In contrast to alternative coatings such as galvanic processes, PVD/TiN coating does not use any toxic or environmentally harmful substances.

PVD/TiN coating of large surfaces (sheets) is carried out with the aid of ARC evaporation, in which the "target material", which is present in the form of a solid, is made to evaporate by means of an electric arc so that it can later be applied to a workpiece.

For the PVD/TiN coating of construction and other small parts mirrorINOX has a further, separate coating line, which was also specially designed and constructed for this purpose.

The modern, state-of-the-art technology of PVD/TiN coating enables stainless steel surfaces to be coloured with a controlled, raw-material-independent and always very precisely reproducible, colour-uniform process.

Additionally, the highly thin layers achieved are extremely natural metallic and lively in their appearance, which distinguishes them seriously from alternatives such as wet painting, powder coating or similar.

For more information on these stainless steel colouring processes, please see our offers for PVD coating and stainless steel surface treatment.

nanoINOX® AFP/ETC coating process

mirrorINOX applies the nanoINOX® AFP/ETC coating, which is based on the latest SolGel technology and is usually between 2 and 5 my thick, to the surfaces consisting mainly of stainless steel sheets with the aid of a multi-head atomiser. Afterwards, the transparent coating or the coating enriched with coloured pigments is heated up to 250°C in a continuous flow heater and baked on.

It is thus possible to produce an enormous range of colours, surface finishes or designs. Specific properties such as colour, hardness, temperature stability, corrosion and chemical resistance, transparency and flexibility (formability) can also be controlled in the layers by incorporating a wide variety of elements.

In addition to the variety of visual and designing possibilities, sol-gel coatings also produce other properties such as Easy-To-Clean (ETC), AntiFingerPrint (AFP) and a lotus effect.

They can be used both indoors and outdoors, they protect against pollutions and dirt such as fingerprints, graffiti and many more. This saves cleaning and maintenance costs. The coatings are also extremely robust against weathering.

Additional, technical functions of the coating, such as antibacterial or electrically insulating properties, are also possible.

You can find more information on these processes with regard to stainless steel colouring on our specialist pages on nanoINOX® and stainless steel surface treatment. We will explain both processes in more detail in the next paragraph.

Stainless steel colouring at mirrorINOX: Our selection and our process

With both processes carried out by mirrorINOX, the PVD/TiN coating process and the nanoINOX® AFP/ETC coating process, the most diverse surfaces of the stainless steel grades/alloys 1.4016, 1.4301, 1.4401/1.4404, 1.4435 and even 1.4462 and 1.4571 can be coloured. With the nanoINOX® AFP/ETC coating process, even metals such as aluminium and others can be colour coated.

PVD/TiN coating process

The advantageous properties of the PVD/TiN coating process in keywords:

• Environmentally friendly manufacturing process
• No toxic or environmentally harmful substances are produced
• Wide variety of colours and finishes
• High colour uniformity on each individual panel
• High colour uniformity from panel to panel
• Each individual panel is individually measured (reflectance, gloss, roughness and LAB colour values), checked for deviations and documented
• Therefore, each individual sheet has its own identity and is traceable at any time
• Colour uniformity of less than one point on the LAB scale possible
• Excellent reproducibility

The metallic and visually extremely attractive shades of the PVD/TiN coating process range from Champagne-TiN, Gold-TiN and Brass-TiN to Rose Gold-TiN and Bronze-TiN to Anthracite-TiN and Black-TiN. Combined with a wide variety of base surfaces, they give the stainless steel surfaces an exclusive appearance and create brilliant application examples in architecture and product design, both indoors and outdoors.

nanoINOX® AFP/ETC coating process

The advantageous properties of the nanoINOX® AFP/ETC coating process in keywords:

• Environmentally friendly manufacturing process based on SolGel technology
• No toxic or environmentally harmful substances are produced
• Greatest variety of colours and finishes (e.g. "blackest" tone compared to INCO or PVD)
• Highest colour uniformity on every single sheet
• Highest colour uniformity from sheet to sheet
• Each individual sheet is individually measured (reflectance, gloss, roughness and LAB colour values), checked for deviations and documented.
• Therefore, each individual sheet has its own identity and is traceable at any time
• Colour uniformity of less than one point on the LAB scale possible
• Excellent reproducibility
• AFP/ETC features: AntiFingerPrint and Easy-To-Clean, Anti-Graffiti
• Cost-efficient, as less cleaning is required
• Environmentally friendly, as less cleaning is required = Less water consumption, less chemicals
• Cleaner surfaces + better cleaning results = greater hygiene
• Best price-performance ratio
• Shortest delivery times

The nanoINOX® AFP/ETC coating process already offers an almost unlimited number of different colours, shades and finishes (e.g. matt or glossy). mirrorINOX is constantly developing new variants and nuances and expanding the spectrum. Depending on the order volume, special colours are also created exclusively according to customers' specifications. Here is an excerpt of the different possibilities:

• CLEAR nanoINOX® (transparent)
• Champagne Classique nanoINOX®
• Gold Rosé nanoINOX®
• Abyss Black nanoINOX®
• Black Matt nanoINOX®
• Black Electrum nanoINOX®
• Blue Electrum nanoINOX®
• Green Electrum nanoINOX®
• White nanoINOX®
• uniqueSURPHACE®
• and other customized colours and designs on request

Blackening stainless steel

We are often asked whether stainless steel can be blackened in the same way as brass.

Black stainless steel or blackening stainless steel is possible at mirrorINOX with the PVD/TiN coating process as well as with the nanoINOX® AFP/ETC coating process completely without the use of environmentally harmful galvanic substances such as pickling or similar.

The experts at mirrorINOX can blacken stainless steel in the colours dark grey, anthracite and black to deep black.

Black stainless steel can thus be produced for sheet metal as well as for structural and small parts and accessories made of stainless steel.

Particularly with the nanoINOX® AFP/ETC coating process, it is possible to colour stainless steel black in deep black (matt and glossy) shades due to the thickness of the layers and the process technology.

Can stainless steel be anodised?

The anodising process, i.e. the electrolytic oxidation of aluminium (EL-OX-AL), is only found in the surface finishing of aluminium sheets. These anodised surfaces are not applicable to stainless steel.

When talking about anodic oxidation, we are referring to materials other than stainless steel, such as aluminium. Therefore, the question whether stainless steel can be anodised must strictly be answered in the negative.

mirrorINOX: Expertise from stainless steel colouring to nano-coating

Whether it's stainless steel colouring, grinding, polishing, mirror polishing, shot blasting, pattern rolling or coating: When it comes to surface treatments of stainless steel and other metals, you'll find mirrorINOX to be the ideal partner. This is where our core competence and passion lie.

Expert advice and professional execution are the guarantee for a result that will also satisfy you.