Case Histories » Public Sector

Corrosion Engineering Assessment of a Heating System

Stains on cast aluminum heat exchanger indicating a glycol leak
View of dark stains on one side of the cast aluminum heat exchanger indicating a glycol leak
Enlarged view of the brown colored/stained crystals
An enlarged view of the brown colored/stained crystals growing in an area of the heat exchanger
“Sand Cast” surface indicates insignificant corrosion has occurred
Top view of the rod-like surface showing a group of white deposits growing
Top view of the rod like heat exchanger surface (exposed to the burner) showing a group of white deposits growing

Specimens

2.0-inch inner diameter steel pipe and cast aluminum heat exchanger.

Environment

Maintenance building.

Background: It was learned that the incorrect type of glycol had been used in the heating system since 2012. The objective of this corrosion investigation was to assess if any corrosion damage had been done to the heating system.

Service Life

Approximately five years.

Findings

Inspection of the cast aluminum heat exchanger showed no evidence of corrosion or metal loss. Inspection of the 2.0-inch ID steel supply pipe showed negligible corrosion, indicating that the water treatment was satisfactory. Inspection of the inside of the aluminum heat exchanger revealed significant deposits of casting sand still present between the internal fins. This casting sand/binder will continue to loosen and mix with the glycol heating fluid. The white deposits present on mid-portions of the aluminum heat exchanger appeared harmless and are normally expected when high-temperature combustion occurs in the presence of aluminum.