Q.: During construction of a new sewage collection system it was found that the aluminum manhole steps embedded in the concrete manhole pipe had not been tar-coated before installation. All published articles we have found about galvanic effects of aluminum in concrete have said a protective coating should be applied to the aluminum to eliminate the possibility of corrosion.
The manhole manufacturer claims that the aluminum steps do not come in contact with concrete containing calcium chloride but are in fact set in a proprietary patching compound. This contains, among other things, Portland cement, sand, a synthetic organic polymer, an organic plasticizer and hydrocellulose thickener and no calcium chloride. Will there be a corrosion problem in the future?
A.: It is not entirely clear what all of the ingredients are—that is, whether the synthetic organic polymer is a latex binding agent or a water-reducing agent of some kind, and what the organic plasticizer is. Nevertheless we doubt that the patching compound would attack aluminum.
On this basis we would not suggest having the aluminum steps removed, dipped and reset. You might be justified, however, in asking for a brief warranty, such as a year or two, during which you could watch the performance of the steps and have some tests made if you see anything suspicious, such as cracking around the steps or buildup of salts at the point where the aluminum steps enter the concrete.