High-Quality special steel
for metal garden products
In Germany the name CORTEN steel*) stands for weatherproof construction steel that continuously develops a barrier layer as part of a weathering process. This layer protects the elements from further corrosion and results in a characteristic patina in earthy and warm color shades. Corten steel has got a service life over average. It does not need to be varnished and is recyclable. We only use especially top-quality grade S355J2W+N, material number 1.8965, that can be bended and – with the right filler material – can also be welded.
*) The name COR-TEN (steel) consists of two parts. The first part COR stands for CORrosion Resistance, the second part TEN stands for TENsile strength. The patent for COR-TEN-Stahl was applied for in the USA in 1932. Worldwide there are a lot of different sorts of weatherproof construction steel.
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Berosten von Cortenstahl
Weiterführende Literatur und Quellennachweis
Corten steel - field of application
For unique quality:
Delivery condition "rolled blank"
How the patina is developed
When the crude steel plates are produced and processed the surface has not yet developed a patina. This patina only develops under natural weathering conditions. The development of a good-looking patina starts after 2 to 3 weeks and is only complete after 1.5 to 3 years. Important for the development of the barrier layer is the alternation between humid and dry weather. If there are surface parts, that are not exposed to weathering, they are excluded from the process of patina development.
Black Stains on corten steel
In the case of air exclusion it may happen that the fresh, slightly rusted surface turns black, e.g. if the material was packed in a tight-fitting foil for transport. This coloring tapers off after a few days of natural weathering. So it is no defect and thus no reason for rejection.
It can also temporarily come to a black color change, when the corten steel surface is touched by dead leaves or plantings over a longer period of time. Remember: After removing the leaves the weathering process is started anew and the patina surface returns.
Pre-oxidizing: color differences
It is hard to believe but it is just as it seems: The same material from the same production lot develops a different first rust coloring, depending on the weathering and the environmental effects.
The rust coloring is mainly influenced by the temperature and the relative humidity. With lower temperatures and higher humidity the color turns darker. Different colorings after the first rusting are leveled out after the progressive weathering of the objects. These differences in color are therefore no defect and thus no reason for rejection.
Imprints from vacuum cup on
When the raw plates are processed, they are gripped automatically at several production stations with the aid of vacuum suction cups and transported for further processing. After the first rusting these cups can leave imprints – sometimes less, sometimes very clearly visible
Among experts these imprints are called “crop circles”. They occur when the surface is disturbed by minimal rest particles of SUPER ROST, which adhere to the cups. The imprints only turn up 12 to 24 hours after the first auburn patina. Under the effect of natural weathering the imprint disappears. If this disappearance has to be fastened, the surface can be mechanically roughened and rusted again.
Note: Imprints caused by vacuum cups on the pre-rusted surface are no reason for rejection.
Corten steel classified as ecological material
Weatherproof construction steel can be classified as ecological material. It has an over-average product life span, does not need to be varnished and is completely recyclable. Corten steel contains minimal amounts (less than 1%) of high-grade copper and chrome, which make it nearly indefinitely durable and avoids rusting through.
Note: Decorative elements or cheap planters are often offered in hardware stores with the designation „patina look“. Normal steel is usually hidden behind it. It can rust through after just a few months in the garden and become a danger to pets and insects.
Is corten steel or construction steel in the garden a risk to your health?
Removing deposits from terrace tiles and natural stone
Rusty deposits, e.g. caused by drain water, can be removed more or less successfully with a suitable rust remover. The cleaning success is mainly determined by: Basic material Quality and quantity of cleaning Suitability of cleaning agents
For acid-resistant floor coverings cleaners on the basis of phosphoric acid are most likely to be successful. In case of little and light stains household remedies are ideal, like table salt in combination with ascorbic acid and water. No acidic cleaners may be used with concrete bound floor coverings. Only cleaners on the basis of tannin have a chance of achieving a sufficiently good cleaning result. Since the surface turns red-purple during treatment, it is essential to ensure proper application to avoid consequential damage. In all cases, test the effect of the cleaner by using a small sample area!
Sealing corten steel
Corten steel as a snail barrier
Suggestion for tender template
„Rolled flat steel. Quality standard weatherproof construction steel corten steel Corten B ASTM A 588, quality S355J2W+N. Material number 1.8965 according to EN 10025-5 with acceptance test certificate. Surface pre-oxidized on all visible sides.”
Metal aheets and cutting
If you need cuttings, sheets or plates of plain or pre-oxidized corten steel we can offer them to you at a very good price. We can do so because we always buy big quantities ourselves. Even small steel traders and many locksmiths purchase their corten steel from us. Also ask for corten steel without “roller skin”. This material is produced by big steel manufacturers exclusively for Gartenmetall®.
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