Performance of Aluminum in Concrete Containing Chlorides.

Results of detailed research and investigation of field problems have demonstrated that chlorides in concrete can cause severe corrosion of alu-minum when coupled to steel. The expansive nature of the corrosion products causes cracking and spalling of concrete cover over embedded aluminum conduit. Chloride anion enrichment, as a result of the galvanic connection, serves to arrest polarization of the aluminum. Production of an aluminum chlorhydroxide product and a specially oriented "cubic" attack pattern have been typical of this reaction in both field and laboratory experiences. A similar ion migration mechanism might be expected for any metal whose composition or state of stress make it anodic to other coupled embedded metals. In chloride-free concrete, aluminum has good resistance to corrosion both alone and coupled to steel and no cracking of concrete has been encountered. It is recommended that chloride additions or contaminations should be avoided in concrete containing embedded metals. If this is not practicable, protective coatings are required and are available. [ABSTRACT FROM AUTHOR]