Cut edge Corrosion

Question 1

What is cut edge corrosion?

Answer 1

• Cut edge corrosion occurs on metal roof sheeting when the protective coating peels back at the lap joint which exposes the metal base to moisture and oxygen leading to corrosion.
• Corrosion can lead to further deterioration of the of the protective coating and eventual perforation of the base metal.

Question 2

What causes cut edge corrosion?
What causes the protective coating to peel back

Answer 2

• Metal roof sheeting has a protective coating such as plastisol which can be damaged which allows moisture and oxygen to reach the base metal and cause corrosion.
• The cutting of roof metal sheets can cause micro-cracking within the protective coating.
• Water can become entrapped at the lap joint by capillarity and dirt which accelerates the corrosion.

Question 3

How do you repair cut edge corrosion?

Answer 3

• Cut edge corrosion is treated by cleaning the affected area to remove defective coatings by chemical stripping, abrasive blast cleaning or high pressure water cleaning.
• The lap joint is then treated using a silicone based paint or polymer topcoat ensuring a minimum width of 75mm.