Case Histories

Public Sector

Severe Graphitic Corrosion in Cast Iron Drain Lines in a Health Care Facility

Cracked and Perforated Elbow of Failed Cast Iron Drain Pipe
Corrosion and Cracking of a Titan 3 1/8 inch Drain Line Elbow This elbow was likely in a horizontal position as this portion of the pipe wall had thinned to 1/16 inch or less.

Environment: Vertical and horizontal waste water drain line located in a health care facility. Pipes were located in both finished walls, and in the crawl space.

Material: Cast iron drain lines are to conform to ASTM A888, the analyzed pipe did not conform to these specifications.

Manufacturer: Titan

Installation Date: approx. 1983

Service Life: approx. 23 years

Mode of Failure: Severe graphitic corrosion, and cracking due to the use of a cast iron material which did not meet specifications for this use.

Findings: The drain line system contained multiple longitudinal and transverse cracks in the cast iron piping. In addition, sever graphitic corrosion had reduced the wall thickness of piping in some locations to 1/16-inch or less, creating holes and leak sites, in some locations, appearing as ‘carbunkle’ leak sites.

Chloride Stress Corrosion Cracking

Circular rosette pattern of corrosion had initiated in the residual stress field produced when the bolt holes were drilled or punched in the web of the purlin
Multiple cracks (20 or more in a 9 cm length had initiated in the outer edge of the flange. Multiple cracks, orientated at approximately 45 degrees, had initialed in the outer surface of the 45 degree bend (denoted by arrows)
View of Carly climbing a flight of stairs to reach the forensic examination level where the roof purlins are located
View of Carly using the Dino-Lite digital microscope in order to examine the surface of the roof purlin at 59x magnification

Specimen: Roof purlin was cold formed corner and sheared edge.

Material: Type 304 Stainless Steel

Environment: Indoor Swimming Pool

Background: The pool had to be closed down early due to rust falling into the pool.

Service Life: The Type 304 stainless steel roof purlins had been in service for approximately 6 years.

Findings: Stress corrosion cracking has initiated at many location in the purlins where cold work, either by bending or punching, had been imparted into the Type 304 Stainless Steel. The structural designers and the persons supplying the Type 304 Stainless Steel Purlins should have been aware that a very corrosive, high chloride environment exists at ceiling level in an indoor swimming pool. In Europe, Type 304 stainless steel structural members have been banned for approximately 20 years due to numerous cases of stress corrosion cracking in many European countries.

This investigation was featured in the Winnipeg Free Press: Portage La Prairie Suing Over Pool Roof.

Corrosion Engineering Assessment of a Heating System

View of dark stains on one side of the cast aluminum heat exchanger indicating a glycol leak
An enlarged view of the brown colored/stained crystals growing in an area of the heat exchanger
Heat exchanger cross section showing deposits of sand remaining from casting process packed between the 3.0mm high interval fins. “Sand Cast” surface indicates insignificant corrosion has occurred
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 engineering investigation is to assess if any corrosion damage has been done to the heating system.

Service Life: Approximately 5 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 is 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 appear harmless and are normally expected when high temperature combustion occurs in the presence of aluminum.