The first article is a review on testing methods and the second article concerns coupled stainless steel and carbon steel rebar in chloride-containing concrete.

-To be a cost attractive alternative to carbon steel rebar, stainless steel reinforcement should be used selectively with only the outer layers of the reinforcement in stainless steel while the rest is made of carbon steel, informs Sara Randström, research engineer at Avesta Research Centre (ARC).

The main problems are to determine to which depth the chlorides penetrate and which stainless steel grade to use. Traditionally, 1.4307 and 1.4404/1.4436 has been used, but also 1.4462 to some extent. The duplex grades are actually to prefer, since they can be hot rolled and still have the required strength. Since the chloride tolerance is crucial, it has to be defined. There are many ways to test the chloride tolerance, which is mentioned in the first paper. Both cast-in methods and in-solution methods exist, and the chloride tolerance often differs between different papers. 

-We have decided to use a method here at Outokumpu Avesta Research Centre where we use a synthetic pore solution and then slowly increase the chloride concentration until corrosion occurs. This method has proven to be a reliable method and the work is now focused on getting chloride threshold level (CCTL) for all our rebar designations, says Randström.

Another issue for the research engineers has been to prove that galvanic corrosion is not an issue in concrete structures:

-When people hear that carbon steel and stainless steel are present in the same structure, they often ask whether galvanic (bimetallic) corrosion is an issue. In the second paper, which is a work that has been performed at Swerea KIMAB, we observed that the corrosion rate of the carbon steel was not affected by the presence of electrically connected stainless steel. This is a conclusion that also has been made by other authors, concludes Sara Randström.

For more information on Stainless Steel Rebar, visit our Stainless Rebar pages or contact:

Murray Adair
Rebar Product Manager
ASR, Sheffield
Email: murray.adair(at)outokumpu.com

Sara Randström
Research Engineer
Avesta Research Centre, Sweden
Email: sara.randstrom(at)outokumpu.com

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For more information on Acom, please contact the editor:

Jesper Gunnarsson
Avesta Research Centre, Sweden
Email: jesper.gunnarsson(at)outokumpu.com