Sacrificial anode system protects concrete

Citation

(1998), "Sacrificial anode system protects concrete", Anti-Corrosion Methods and Materials, Vol. 45 No. 6. https://doi.org/10.1108/acmm.1998.12845fab.005

Sacrificial anode system protects concrete

Sacrificial anode system protects concrete

Keywords Cathodic protection, Concrete, Steel

Concrete balconies, commonly constructed on hotels and other large structures, are susceptible to costly damage from outdoor elements. Penetrating rain, salt spray, or salty sand and chloride admixtures used to mix the concrete can corrode the steel reinforcing bars (rebar) embedded inside. As the rebar rests, it expands in size, causing delamination and spalling of the concrete.

The repair and patch methods typically used on concrete balconies only fix the damaged areas, with the possibility of additional repairs in the near future. This method can actually speed up damage in areas of the balcony adjacent to the patch, creating a new corrosion cell between the newly patched concrete and the unrepaired area adjacent to it.

In an effort to treat the cause of this problem instead of waiting until damage has been done, 3M's Industrial Tape and Specialties Division has developed a new sacrificial anode system especially for concrete balconies. The system, 3M Zinc-Hydrogel Anode 4727, keeps the rebar in a cathodically protected state for long-term protection of the concrete.

The zinc metal foil product, coated with a hydrogel adhesive, is available in 10in.-wide by 90ft -long rolls. Pieces of the desired length are cut from the roll, the protective film liner is removed, and the adhesive side is applied to the concrete surface. A wire connects the zinc to the rebar, enabling the zinc to become the corroding, or active, member and the steel rebar to be put in a non-corroding, passive state. The coupling of the two dissimilar metals supplies the cathodic protection current without the need for an external power supply.

The system can be applied to either the top or underlying surface of a concrete balcony. A benefit to top surface installation is that carpet can be laid over it. Carpets are sometimes avoided on balconies because they retain moisture, which can accelerate the corrosion of rebar. With the 3M system in place, moisture is not a problem. The product can also be painted.

Further details are available from 3M Industrial Tape and Specialty Division products. Phone: +1 800 567 1639, ext. 1417.