Photo Gallery Series H: Structural Corrosion Insulated…
Photo Gallery H04: Mechanical Components Unlike No Images.Please upload images in images manager section. Click on Manage Images button on the right side of the gallery settings.
Photo Gallery H02: Structural Corrosion Unlike No Images.Please upload images in images manager section. Click on Manage Images button on the right side of the gallery settings.
Photo Gallery H01: Corrosion at Pipe Supports Unlike …
Photo Gallery G2: Brass Dezincification Dezincification is more of a chemical transformation than a corrosion event. It occurs to brass pipe after a long period of service, typically at or about 80 years, and is greatly dependent upon the type of brass pipe installed in combination with the composition and aggressiveness of the local water supply. The problem arises from the natural affinity of water for zinc, a chemical element from which brass pipe is made. Red brass has a lower percentage of zinc and is far less impacted by dezincification, whereas more commonly used yellow brass has a much higher percentage of zinc and therefore is far more vulnerable. Common signs of dezincification are round chalk like deposits on the pipe surface, which represent areas where the zinc has been leached out or been removed to produce a more porous form of copper. If removed or cut open for visual inspection, similar chalk like deposits are also viewed inside. Where no such markings are present, a metallurgical lab analysis is required to identify the condition. As certain photos in our gallery illustrate, removing the external deposits produces a condition where the brass pipe has seemingly been inlaid with copper. …
Photo Gallery G4: Graphitic Corrosion This is a relative rare form of corrosion occurring to grey cast iron pipe installed underground, and in a moist or wet environment. It can take various forms from localized severe external pitting to sheer fractures. One common issue is the support of such pipe on wood – which leaches out the graphite from the pipe wall to produce a much more fragile material likely to fail. …
Photo Gallery G3: Ductile & Cast Iron Pipe Failure Every possible problem exists in the fitness for service assessment of cast iron and ductile iron pipe. The material itself is the most difficult to ultrasonically test. Both internal and external surfaces begin rough and deteriorate over time to interfere with the sound signal. Corrosion characteristics vary widely. Unlike other piping materials which require the almost complete penetration through the pipe wall for a failure to occur, cast iron and ductile iron pipe fractures and splits once sufficient wall thickness is lost to allow its bound stresses to release – an event which cannot be reliably predicted. Nevertheless, most older cast iron pipe can provide near 85 years or reliable service. Eventual failures are typically in the form of either longitudinal fractures or multiple pinholes. Cross-sectional separations are also a threat, as some of our photographs show. Horizontally oriented pipe is always more vulnerable although “channeling” can produce the same fracturing at vertical lines. Although unpressurized and without the greater water damage threat that exists for most HVAC systems, entire sections of the pipe wall can fracture away. Because such piping systems are unpressurized, early leaks are typically addressed with repair…
Photo Gallery Series G: Material Specific Issues The most common form of corrosion involved the impact of water against carbon steel to produce an iron oxide rust product. Either the visual presence of rust, discolored water, or some failure event defines this form of corrosion activity. Although the most common, other forms of corrosion exist specific to less common piping materials such as copper, brass, galvanized steel, and cast iron – with each exhibiting different failure modes. Many of those materials are represented in the various Photo Galleries presented, with four of the least common corrosion mechanisms shown here. This series of Photo Galleries relates to some other piping materials and the modes of failure they exhibit.
Photo Gallery D6: Obvious Problems Insulation is important to many piping systems in terms of energy savings but far more critical as a safeguard to the pipe itself. For any cold water service, moisture penetrating through the insulation to condense can produce substantially greater external deterioration than what has occurred internally, and has been documented to produce entirely unexpected and massively costly failures. Although much of such deterioration could be avoided by first protecting the pipe using an effective rust preventative coating, such is never performed due to the mistaken belief that insulation is all that is necessary. Since the slightest defect to the insulation means an opportunity for water and moisture to enter, damaged or missing insulation provides an obvious clue to an otherwise hidden problem. Even where its outer condition appears pristine, the simple failure to install a hard shell outer moisture barrier and silicone or mastic seal every joint and seam can result in a similar level of deterioration. Whether damaged from foot traffic or other maintenance demands, outdoor weathering, or old age, insulation condition should be immediately noticeable to anyone in the area, and especially to those responsible for such important infrastructure. Like many deficiencies we…
Photo Gallery I5: Improper Galvanizing Galvanized steel pipe has dramatically transformed over the past 150+ years. Since earliest examples, the quality of galvanized steel has declined to the point where today, it cannot be relied upon for long service under almost any conditions. Old examples of galvanized steel had such a thick coating of zinc that it could often be sliced away in slivers with a sharp blade; providing reliable service since 1896. In another more recent CorrView investigations of one of America’s earliest universities built in 1877, the original galvanized wrought iron pipe was still providing service; only now reaching retirement after 147 years. In contrast, new galvanized steel pipe appears with such a thin coating of zinc that eye protection must be used when rolling a groove in order to protect against small flying shards of razor sharp zinc. While American made products still exceed the quality of foreign produced galvanized steel, failures of large diameter schedule 40 galvanized steel pipe have occurred in under 5 years. For dry and pre-action fire sprinkler system, this change in quality has been highly detrimental; finding most such systems to achieve at most 20 years of service before requiring replacement. Many…