What surface finishes are available for stainless steel?

Stainless steel is an indispensable material in modern industry and architecture due to its corrosion resistance and durability.

Surfaces & Finishes

While mill production primarily meets functional requirements, we transform these base products into design-led surfaces of the highest quality. mirrorINOX in Cleebronn finishes stainless steel sheets using mechanical and chemical processes to achieve specific levels of reflectivity, textures and functional coatings. In this way, we create solutions for façades, elevator construction and demanding industrial applications where aesthetics and durability are equally important.

What Is Stainless Steel? – Definition and Basics

The term stainless steel encompasses corrosion-resistant steels with a chromium content of at least 10.5% and a carbon content of no more than 1.2%. This chromium content is essential for the formation of a protective passive layer on the material surface. In technical practice, a distinction is made between different microstructures, with austenitic chromium-nickel steels being the most relevant for surface finishing. All finishing processes are based on the mill finishes defined in standards such as EN 10088-2. These fundamentally distinguish between hot-rolled (code 1) and cold-rolled (code 2) products.

Designations and Synonyms – Relevant Standards and Names

Stainless steel is identified using various national and international systems. Familiarity with these designations is essential for the precise specification of surface finishes.

V2A and V4A – The Classic Groups

The terms V2A (test melt 2 austenite) and V4A are historical designations that continue to be used in German-speaking countries as synonyms for standard alloys. V2A generally includes grades such as 1.4301, while V4A offers increased resistance to chlorides due to the addition of molybdenum (e.g. 1.4404).

Material numbers according to DIN EN 10027

The European system uses five-digit numbers for unique identification. The number 1.4301 denotes the classic chromium-nickel stainless steel, while 1.4404 is used for more demanding environments. These numbers form the basis for our production planning in Cleebronn.

AISI and ASTM Standards

In the Anglo-American market, the American Iron and Steel Institute (AISI) system predominates. Grade 1.4301 corresponds to AISI 304, while 1.4404 corresponds to AISI 316L. These standards also define surface finishes such as "No. 4" (brushed) and "No. 8" (mirror-polished).

Chemical Composition

The chemical composition determines the physical properties and suitability for subsequent finishing processes such as PVD/TiN coatings or polishing.

Iron (Fe): The main constituent of the alloy.
Chromium (Cr): At least 10.5% to form the protective chromium oxide layer.
Nickel (Ni): Stabilizes the austenitic microstructure and improves corrosion resistance.
Molybdenum (Mo): Increases resistance to pitting corrosion in chloride-containing environments.
Carbon (C): Kept at a low level in corrosion-resistant steels to prevent intergranular corrosion.
Manganese (Mn), silicon (Si) and nitrogen (N): Used to optimize strength and processability.

Properties

The properties of stainless steel vary depending on the alloy and surface condition. We take these parameters into account in every finishing process.

Mechanical properties

Stainless steel is characterized by high toughness and good formability. Tensile strength and yield strength are crucial for structural applications in façade construction. Through work hardening during the rolling process, we increase the hardness of the base material.

Physical Properties

Compared with unalloyed steel, the material has lower thermal conductivity and a higher coefficient of thermal expansion. This requires precise planning of expansion joints for welding and large-area façade cladding.

Corrosion resistance

The passive layer regenerates automatically after mechanical damage when exposed to oxygen. We enhance this protection with finishing processes such as electropolishing or the nanoINOX® coating, which reduces surface energy and prevents deposits.

Magnetism

Austenitic stainless steels such as 1.4301 or 1.4404 are virtually non-magnetic in the solution-annealed condition. However, cold forming – for example during cold rolling (e.g. finish 2B), press braking or deep drawing – can cause strain-induced martensite to form in some areas. This results in slight magnetism, which is technically harmless and does not adversely affect the material’s corrosion resistance.

Applications and industries

The choice of the appropriate surface finish depends on the specific application and its requirements.

Architecture and façade construction: Use of mirror-polished finishes such as Perfect Mirror No. 10® for visual highlights and functional reflection.
Elevator construction: Use of textured and coated sheets (nanoINOX®) to increase scratch resistance and reduce fingerprints.
Food industry: Preference for smooth finishes (2B or 2R) to meet strict hygiene standards and facilitate cleaning.
Yacht building: Use of highly corrosion-resistant grades (V4A) with a high-gloss polish for resistance to salt water.
Product design: Use of colored PVD/TiN coatings for exclusive interior solutions.

Overview of international standard designations

For global trade and precise specification, we use the standardized designations defined in EN 10088-2.

1D: Hot-rolled, heat-treated, pickled. A scale-free, matt surface for industrial applications.
2D: Cold-rolled, heat-treated, pickled. Smoother than 1D, but without gloss.
2B: Cold rolled, heat treated, pickled and lightly skin-pass rolled. The most commonly used mill finish.
2R (BA): Cold rolled, bright annealed. A reflective surface, but without a non-directional mirror finish.
2G: Mechanically ground with a specified grit (e.g. K240 or K320).
2J: Brushed or satin polished for a refined visual texture and a uniform appearance

Stainless steel finishing – mirrorINOX services

At our Cleebronn site, we finish stainless steel beyond standard specifications. Since 2016, we have been using state-of-the-art equipment to produce surfaces that meet the highest aesthetic and technical standards. We manufacture our proprietary Perfect Mirror No. 10®, regarded as the world’s leading mirror polish for architectural applications. Our VIBES processes create non-directional finishes, while the BEADS series stands out for its precision bead blasting. Our Sol-Gel-based nanoINOX® coating not only adds colour to the sheets, but also provides functional benefits such as an anti-fingerprint effect. Thanks to our ISO 9001 certification, we guarantee complete documentation and reproducibility for every batch.

FAQ

Frequently Asked Questions

Which stainless steel finish is best suited for outdoor use in coastal areas?

For applications near the coast, we recommend at least grade 1.4404 (V4A) combined with a smooth surface finish, such as mirror-polished or nanoINOX®-coated. Smooth surfaces minimise the adhesion of chloride salts, significantly reducing the risk of pitting corrosion. In Cleebronn, we manufacture surfaces specifically optimised for these conditions and designed for easy cleaning.

What is the difference between 2R (bright annealed) and a mirror polish from mirrorINOX?

The factory finish 2R is produced by bright annealing and, while glossy, is not free from rolling marks and haze. 2R (also known as BA – Bright Annealed) is annealed in a protective atmosphere to prevent oxidation. Although reflective, the manufacturing process leaves minimal directional rolling marks, a slight “orange peel” texture and light haze. It is a reflective mill finish, but not an optical mirror. By contrast, a mirror polish such as Perfect Mirror No. 10® from mirrorINOX is a mechanical polishing process that removes all defects. With a true mechanical mirror polish, the surface is progressively abraded and levelled in several stages. Rolling defects, microscopic roughness and directional marks are thus completely eliminated. The result is a clear, non-directional reflection visually comparable to glass mirrors, while offering the shatter resistance of stainless steel. This is precisely what distinguishes high-quality non-directional polishes (such as No. 8 or No. 10) from standard sheet. It also perfectly highlights the key advantage of stainless steel over glass: impact and shatter resistance, for example in vandal-prone areas or elevator construction.

How can I effectively clean finished stainless steel surfaces in public spaces?

Refined surfaces, particularly our nanoINOX®-coated stainless steel sheets, have easy-to-clean properties. As a rule, clean water or neutral cleaning agents are sufficient. The smooth texture and functional coating reduce cleaning intervals and the use of chemicals. Dirt adheres more slowly and can be removed more quickly. This directly results in lower life-cycle costs (LCC/Life-Cycle Costs) for building cleaning and meets modern sustainability criteria (e.g. DGNB, LEED).