Electrolysis between dissimilar metals is a common trap for roofs. Zincalume steel and colorbond roof sheeting do not like contact with lead, copper or stainless steel. When lead is in contact with zincalume metal and there is moisture between them, a small electric current is generated and the ‘weaker’ material (zincalume steel) sacrifices itself by ‘rusting’. This leads to premature deterioration of the protective coating of the metal roof sheet. The two videos below show an example of this problem: