Corrosion of Condenser Piping

Material: Carbon steel
Environment: Cooling water
Issues: Materials selection, water treatment, galvanic corrosion

Exponent investigated the cause of corrosion and deposition in one-inch diameter cooling-water condenser piping in an office HVAC system.  Corrosion resulted from tuberculation due to the presence of oxygenated water in contact with black-steel piping, compounded by ineffective water treatment.  Galvanic corrosion of the steel also occurred at connections with brass gate-valves.

Erosion and Corrosion of Rubber-Lined Steel Pipeline

Material: Rubber-lined carbon steel
Environment: Seawater/mine tailings
Issues: Polymerization, erosion/corrosion

Exponent investigated the failure of a rubber-lined steel pipe carrying seawater-based tailings slurry from a mine.  We concluded that failure was due to inadequately cured rubber lining, which delaminated and led to subsequent erosion/corrosion of underlying steel pipeline.

Pitting Corrosion of Stainless-Steel Piping

Material: 304L stainless steel
Environment: HCl fumes
Issues: Pitting corrosion

Exponent performed a condition assessment of 304L stainless-steel piping that had been exposed to a hydrochloric acid spill.  We determined the extent and severity of pitting using metallography and scanning electron microscopy, and made recommendations as to which piping needed to be replaced.

Corrosion of Pre-Stressed Concrete Water Pipes

Materials: High-tensile-strength steel wire, concrete/mortar
Environment: Potable water (inside), soil (outside)
Issues: Localized corrosion, stress-corrosion cracking

Exponent investigated the corrosion of a pre-stressed concrete pipeline (concrete pipe encased in high-tensile-strength steel wire wrapping) in Arizona.  Corrosion resulted from the migration and concentration of chloride ions at the steel wire, which led to localized corrosion and stress corrosion cracking.  Chlorides were present in the soil and the water being carried, which was leaking within tolerances.  Wet and dry cycling drove migration and concentration mechanisms.

Corrosion of Boilers and Boiler Water Chemistry

Materials: Steel
Environment: Boiler water
Issues: Overheating, boiler operation, water chemistry

Exponent investigated a series of boiler tube failures in an industrial package boiler.  Our investigation included an inspection, review of engineering and operational documentation, and testing and analysis.  We determined that the tube failures were caused by overheating (inadequate water circulation) as a result of improper boiler operation, and poor boiler water chemistry control.

Corrosion of 55% Al-Zn Coated Steel Roofing Panels

Materials: 55% Al-Zn coated steel (Galvalume®)
Environment: Indoor atmospheric
Issues: Under-insulation corrosion

Exponent investigated the cause and extent of corrosion of 55% Al-Zn coated steel roofing panels at a warehouse facility in Georgia.  Corrosion on the underside of the panels was due to prolonged exposure to wet insulation, as well as high humidity between the roof and vapor barrier.  Exponent advised on remedial measures to minimize further corrosion.

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