This paper describes the causes of corrosion of metal street lighting columns, and possible methods of reducing the corrosion rate to a very low value. The cost of corrosion control can be as little as 1-2% of the total cost of installing the column, and it will be recovered many times by the resulting extension of the column's life. Metal corrosion is an electrochemical process, where a metal interacts chemically with its environment. As the process can be complex, corrosion can be difficult to predict. Potential corrosion problems can be reduced by asking six specific questions before installing new columns. Columns can suffer from damaging corrosion both above and below ground level. Techniques for monitoring and detecting corrosion above ground are well established and easily available; the method used most often is ultrasonics. One of the very few techniques for monitoring corrosion at the column root, that do not have to dig it out, is an electrical technique based on linear polarisation theory. The current methods of controlling column corrosion are: (1) coatings; (2) tape; (3) cathodic protection; (4) sacrificial anodes; and (5) impressed current systems. Finally, the paper outlines the results of some surveys of columns at two places in the UK, and discusses the economics of corrosion and its prevention.
Samenvatting