Corrosion denting

Plain dents containing corrosion, dents containing stress corrosion cracking, and dents affecting ductile girth welds or seams may be repaired with either a full encirclement sleeve with open ends or with ends welded to the pipe. 

Failure to condemn a cylinder when required (e.g., permanent expansion exceeds 10% of total expansion [5% for certain special permit cylinders], internal or external corrosion, denting, bulging, evidence of rough usage). 180.205(i) 7,500 to 13,500. 

Dents in tubing can induce erosion failures, especially in soft metals such as copper and brass. Welding and improper heat treatment of stainless steel can lead to localized corrosion or cracking through a change in the microstructure, such as sensitization. Another form of defect is the inadvertent substitution of an improper material. 

The key properties here are hardness and wear resistance, ability to. stand minor knocks and dents without cracking and resistance to various domestic chemicals. These vary with type of appliance, e.g. detergent solutions are important for washing machines, while a fridge will be required to withstand fruit juices, ketchup and polishes. Good colour and appearance in white and mainly pastel shades will be expected. Corrosion resistance is required, especially for washing machines, and domestic appliances frequently have to withstand humid conditions in kitchens. 

Zero solids treatment (ZST) is a further enhancement of AVT and MT programs and, as its name suggests, the program employs extensive pre- and post-treatment equipment to ensure the highest possible FW and BW purity. ZST has been employed in the secondary circuits of nuclear-powered SGs as an aid in the prevention of SCC, crevice corrosion, and denting, especially where condenser cooling is effected by the use of brackish or estuarine waters. 

The precise chemistry selected depends on the system design and the propensity for corrosion problems such as denting, tube or tube sheet crevice corrosion, and SCC of stainless steel (by chlorides) and nickel-based alloys (by lead). 

T. Fusayama, T. Katayori, S. Nomoto, Corrosion of gold and amalgam placed in contact with each other, J. Dent. Res. 42 (1963) 1183-1197. 

Dent Wed P (1977) A review of the history and practice of patination, NBSSP 479. Proceedings of a Seminar, Corrosion and Metal Artifacts - A Dialogue Between Conservators and Archaeologists and Corrosion Scientists held at the National Bureau of Standards, Gaithersburg, Maryland, March 17 and 18, 1976, 77-92. 

Heads and shell of exchangers andpressure vessels. These containment elements should be free of corrosion, distortion, obvious cracks, dents, bulges, blisters, and signs of threatening conditions or pending leakage. 

Abrasion removes protective oxidized metal and polarized coatings to expose unoxidized metal, in addition to removing metal particles. Forms microscopic grooves and dents for concentration cell corrosion. Increases microscopic surface area exposed to corrosion. Removes strain-hardened surface layers. Cracks brittle metal constituents, forming sites for impact hydraulic splitting. Plastic deformation by high-stress metal-mineral contact causes strain hardening and susceptibility to chemical attack. 

A number of methods have been devised to protect metals from corrosion. Most of these methods are aimed at preventing rust formation. The most obvious approach is to coat the metal surface with paint. However, if the paint is scratched, pitted, or dented to expose even the smallest area of bare metal, rust will form under the paint layer. The surface of iron metal can be made inactive by a process called passivation. A thin oxide layer is formed when the metal is treated with a strong oxidizing agent such as concentrated nitric acid. A solution of sodium chromate is often added to cooling systems and radiators to prevent rast formation. 

Use of aluminum in the place of steel has two benefits, such as the lighter nature of aluminum compared to steel and better corrosion resistance than steel. New designs and aluminum alloys have resulted in some automobiles made entirely with aluminum including the frame. Polymers have been used to a greater extent as body panels in place of steel. Polymer panels are both corrosion and dent resistant. Automobiles must be designed to use the polymer panels, as the panels do not aid in the structural rigidity of the automobile. 

K. Nakamura, Y. Takada, M. Yoda, K. Kimura, O. Okimo, Galvanic corrosion offerritic stainless steels used for dental magnetic attachments in contact with an iron-platinum magnet, Dent. Mater. 27 (2008) 203-210. 

A Cadillac hood assembly includes a complex-shaped SMC inner panel that is bonded to an SMC outer panel. The outer panel has a Class A finish. The hood surface has a four-sided, tapered design and includes steel hinges, brackets and the hood latch. Here is an example where SMC has the abhity to create high style, lower vehicle weight, reduce tooling costs and resist corrosion and denting. 

J.O. Grippo, M. Simring, S. Schreiner, Attrition, abrasion, corrosion and abfraction revisited a new perspective on tooth surface lesions, J. Am. Dent. Assoc. 135 (2004) 1109-1118. 

Corrosion control as a result of design should be noted here. The design of oil and gas facilities should be done in such a way that there is no room for stagnation, especially on separators, treatment units, or pipelines, because stagnant areas contain some residual materials that over time could cause internal corrosion through pitting, while bulges or dents should also be avoided to curb external facility corrosion. 

Figure 4.4.42. Schematic representation of denting corrosion in PWR steam generators.

Fathi MH, Salehi M, Saatchi A, Mortazavi V, Moosavi SB (2003) In vitro corrosion behavior of bioceramic, metallic, and bioceramic-metallic coated stainless steel dental implants. Dent Mater 19(3) 188-198... 

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