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Cast iron pipe was superseded by ductile iron pipe, which is a direct development, with most existing manufacturing plants transitioning to the new material during the 1970s and 1980s. Ductile iron pipe is different than cast iron, because the introduction of magnesium during the casting process causes the graphite to form spheres (graphite ...
In sewerage areas where biogenic sulfide corrosion is expected, acid-resistant materials like calcium aluminate cements, PVC or vitrified clay pipe may be substituted to ordinary concrete or steel sewers. Existing structures that have extensive exposure to biogenic corrosion such as sewer manholes and pump station wet wells can be rehabilitated.
Stress-Corrosion-Cracking-Quench-Pipe-1.4541-01. Stress corrosion cracking (SCC) is the growth of a crack in a corrosive environment. [53] It requires three conditions to take place: 1)corrosive environment 2)stress 3)susceptible material. SCC can lead to unexpected sudden and hence catastrophic failure of normally ductile metals under tensile ...
In this case, sacrificial anodes work as part of a galvanic couple, promoting corrosion of the anode, while protecting the cathode metal. In other cases, such as mixed metals in piping (for example, copper, cast iron and other cast metals), galvanic corrosion will contribute to accelerated corrosion of parts of the system.
Selective corrosion on cast iron. Magnification 100x Selective corrosion on cast iron. Magnification 500x. Graphitic corrosion is selective leaching of iron, from grey cast iron, where iron is removed and graphite grains remain intact. Affected surfaces develop a layer of graphite, rust, and metallurgical impurities that may inhibit further ...
Anaerobic corrosion is evident as layers of metal sulfides and hydrogen sulfide smell. On cast iron, a graphitic corrosion selective leaching may be the result, with iron being consumed by the bacteria, leaving graphite matrix with low mechanical strength in place. Various corrosion inhibitors can be used to combat microbial corrosion.
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Stress corrosion cracking caused by tension developed in an unsuitably welded reinforcement collar A close-up of the surface of a steel pipeline showing stress corrosion cracking (two clusters of small black lines) revealed by magnetic particle inspection. Cracks which would normally have been invisible are detectable due to the magnetic ...