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Manufacturing Technology Insights | Friday, November 26, 2021
While the material selection is critical for corrosion management, designers cannot overlook the necessity of correct design.
FREMONT, CA: As critical as the material selection is the right design to minimize corrosion. In many structures, the weakest link in corrosion control is a lack of design consideration. Designers should identify the mechanical qualities and strength necessary to assure a structure's corrosion resistance. Additionally, a comprehensive understanding of the corrosion process is necessary. When selecting materials, the designer must consider the environment, intended usage, and corrosion control criteria.
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Design Guidelines
It is more cost-effective to design structures and parts to avoid corrosion than wait for equipment to fail in service. Close collaboration between designers and corrosion experts can be pretty helpful and assured in applications prone to corrosion. Following are a few critical design principles that can assist prevent corrosion:
Wall Thickness Adjustment: Because corrosion is a degrading process, it continuously consumes the material and reduces its thickness. As a result, part of corrosion-resistant design entails accounting for this change in thickness (i.e., wall loss) in pipelines, storage tanks, and other components. A typical rule is to double the wall thickness required for the structure's desired life. On the other hand, the wall thickness must satisfy mechanical criteria for stress, pressure, and weight.
This basic guideline of doubling wall thickness results in an increase in cost and weight. As a result, extensive financial comparisons should be conducted before choosing between these solutions. This regulation is not necessary if reliable corrosion data and appropriate monitoring methods are available.
Ascertain Adequate Drainage: Tanks and other storage containers should be conveniently drainable and cleanable. As a result, all transitions should be seamless, and taps should be strategically placed to allow the tank to be empty.
Reduce the number of bimetallic corrosion cells: Avoid galvanic corrosion by employing similar metals throughout the construction or isolating different materials. (See An Introduction to the Galvanic Series: Galvanic Compatibility and Corrosion for background information.) Corrosion-prone components should be easily replaceable. Additionally, particular parts (wasters) can be employed to attract rust, thereby safeguarding other components. Seals should be used to prevent crevice corrosion, and the pressure on the gaskets should be regulated to prevent liquid penetration into the crevices. In this manner, stagnant water can be avoided in fissures and tight gaps.
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