How the iron clamps and dowels of the temples of the Athenian Acropolis have resisted century-long corrosion

The writer examines the iron clamps and dowels of the Parthenon and the Erechthion from a metallurgical and chemical perspective. The investigation has led to very significant results regarding: a) the possible number of strips used as raw material, and b) the procedure followed by the ancient Greeks of welding them into a plate and subsequently into final double-T clamps or dowels. It turns out that they seem to have intentionally employed a combination of mild and hard steel strips welded together by hot hammering. Occasionally, a hard steel strip would be sandwiched between two mild iron ones or a medium iron strip between two hard steel layers. Macro-investigation of longitudinal inner sections of these clamps proved useful in assessing their structure as compared to the conventional analysis confined to their external surface. The reason is that overlapping, caused during hot shaping, often produces false images which are easily misconstrued. Extensive chemical analyses revealed that impurities were extremely low, especially sulphur content (0.005%).This must have had increasingly effected their high corrosion resistance. On the contrary, mild structural steel used by the Balanos team during restoration, and containing more than 10 times as much sulphur, showed a weak corrosion resistance with the known detrimental consequences on the monuments of Acropolis. The high corrosion resistance of the ancient clamps and dowels suggests that iron ores of high purity must have been used as raw material. Investigation carried out by the writer strengthens the view that such clean ores could exist at Lavrion at that remote time, but most propably they were also imported from other parts of Greece or abroad. Laconia may have been a principal source of rich and clean ores, and the writer does not think that the then existing political tension between Athens-Sparta would have stood as an obstacle to their commercial relations. Finally, he hopes that this research will fill in some of the gaps in our understanding of iron working in Greek antiquity.