Atmospheric Corrosion Resistant Corten Steel - Copper Chromium Alloy Steel

Corten steel (often referred to as Cor–Ten) is a weather resistant steel which could more accurately be termed as an "Atmospheric Corrosion Resistant Steel".

It is a copper chromium alloy steel – this alloy displays a greater level of resistance to atmospheric weathering when compared to other unalloyed steels. It's chemical composition promotes the early formation of an adhering protective layer of rust when exposed to the elements.

Applications of Corten Steel

Aesthetically pleasing to the eye, this finish has become popular with many high profile architects and has been specified and used in a variety of applications in including building fascias, architectural sculptures and bridges. Examples of Corten structures include...

  • The Angel of the North (UK)
  • Matsunoyama Natural Science Museum (Japan)
  • The Center for Contemporary Art (Australia)

The protective layer constantly develops and regenerates over time, reacting to the pollutants in the atmosphere. Consideration should be made with regard to the thicknesses used especially when the material is utilised for structural rather than solely cosmetic purposes.

The benefits of such a steel are immediately obvious – a self–protecting steel is economic, long lasting and easily recyclable. Masteel are a stockist of Corten–B and Corten–A.

Corten Grades & Equivalents

The grades and equivalents of Corten steel are provided in the following table.

Corten EN 10025-5:2004
Corten A S355 J0WP
Corten B S355 J0W & S355 J2W

Mechanical Properties and Thickness Ranges for Corten

The mechanical properties and thickness ranges of Corten steel are provided in the following table.

Thickness (mm)
Strip Products
Plate Products Yield strength
minimum
Tensile stength
minimum
Elongation
miniumum
Corten A 2 – 12 6 – 12 345 485 20
Corten B 2 – 13 6 – 40 345 485 19

Chemical Composition of Corten Steel

The chemical composition of Corten steel is provided in the following table.

Content, % (ladle analysis)
C
(max)
Si Mn P S
(max)
Al V Cu Cr Ni
(max)
Corten A 0.12 0.25–0.75 0.20–0.50 0.07–0.15 0.030 0.015–0.06 0.25–0.55 0.50–1.25 0.65
Corten B 0.19 0.30–0.65 0.80–1.25 0.035 max. 0.030 0.020–0.06 0.02–0.10 0.25–0.40 0.40–0.65 0.40

Example Corrosion Allowances for Untreated Corten B

The example corrosion allowances for untreated Corten B steel are provided in the following table.

Type of atmosphere Corrosion allowance to be added for one side of the
nominal thickness for each 10yr period of working life
First 10 year period mm Each following year period mm
Rural 0.10 0.05
Urban* 0.20 0.05
Industrial** 0.20 0.10
* With the chief impurity in the air being sulphur dioxide
** In addition to sulphur dioxide the air also contains chlorine. Also for locations in the immediate vicinity of salt water

Formability of Corten Steel

The formability of Corten steel is provided in the following table.

Thickness (mm)
(2)–3 (3)–4 (4)–5 (5)–6 (6)–7 (7)–8 (8)–10 (10)–12 (12)–14 (14)–16 (16)–18 (18)–20
Smallest allowable internal bending radius mm
Corten A 6 8 10 12 21 24 30 36 42
Corten B 6 8 10 12 21 24 30 36 42 48 54 60
Values apply to all forming directions

Heat Treatment of Corten Steel

The heat treatment methods for Corten steel are provided in the following table

Heat Treatment Temperature °C Treatment Time
Manner of cooling
Stress relieving 500–600
(target 580)
2 minutes / millimetre thickness, minimum 30 minutes
Slow cooling in the furnace
Normalising 860–940
(target 910)
1 minute / millimetre thickness, minimum 15 minutes
Free cooling in air atmosphere outside the oven

This information has been sourced, reviewed and adapted from materials provided by Masteel UK Ltd.

For more information on this source, please visit Masteel UK Ltd.

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Comments

  1. Robert Anderson BEng (Hons) IEng IncMWeldI Robert Anderson BEng (Hons) IEng IncMWeldI United Kingdom says:

    Is it possible to Ultrasonic test a Corten welded structure and what is the specification and procedure?

  2. Robert Anderson BEng (Hons) IEng IncMWeldI Robert Anderson BEng (Hons) IEng IncMWeldI United Kingdom says:

    Can Corten plate welds be tested by ultrasonic Inspection and what procedures and specifications can I use

  3. John Miles John Miles United Kingdom says:

    Is there any data on CoreTen resistance to crevice and pitting corrosion; particularly in the presence of chlorides?

  4. madhukar Jadhav madhukar Jadhav India says:

    what materialof Nozzle filling compound to be filled in ladle nozzle while making coreten steel.
    should it be chromite based or Zircon based, we have seen nozzle jamming in chromite based material.
    can you Pl.suggest

The opinions expressed here are the views of the writer and do not necessarily reflect the views and opinions of AZoM.com.

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