{"id":81446,"date":"2021-02-04T00:00:00","date_gmt":"2021-02-04T00:00:00","guid":{"rendered":"https:\/\/www.corrosionpedia.com\/2021\/02\/04\/how-to-control-corrosion-by-improving-design"},"modified":"2022-03-01T01:03:29","modified_gmt":"2023-12-09T18:42:30","slug":"how-to-control-corrosion-by-improving-design","status":"publish","type":"post","link":"https:\/\/www.corrosionpedia.com\/2\/1551\/corrosion\/how-to-control-corrosion-by-improving-design","title":{"rendered":"How to Control Corrosion by Improving Design"},"content":{"rendered":"

The proper design to minimize corrosion is as important as the selection of materials<\/a>. In many structures, a lack of design consideration the weakest link in corrosion control<\/a>. Designers should have skills to determine the mechanical properties<\/a> and strength required to ensure that a structure is resistant to corrosion. A background and solid understanding of the corrosion process is important as well. While selecting materials, the designer has to consider the particular environment, use and the corrosion control parameters. These include:<\/p>\n

Design Rules<\/h2>\n

Designing structures and parts to prevent or control corrosion is more cost-effective than waiting for the equipment to fail in service. Close communication between designers and corrosion engineers can be very beneficial and should be ensured in applications where corrosion is likely to be an issue. (For more about the design process, read Corrosion Control Considerations in the Equipment Design Process<\/a> <\/a>.) Here are a few key design rules that can be followed to help prevent corrosion:<\/p>\n

Adjust Wall Thickness<\/strong><\/p>\n

Because corrosion involves the degradation<\/a> of materials, the process continuously eats up the material and decreases its thickness. Therefore, part of corrosion-resistant<\/a> design involves making allowances for this reduction (i.e., wall loss<\/a>) in the thickness in pipes, storage tanks and other parts. A general method is to make the wall thickness twice of that which is required for the desired life of the structure. However, the wall thickness must meet mechanical requirements for stress<\/a>, pressure and weight.<\/p>\n

This general rule of using doubled wall thickness adds extra cost and weight. Therefore, detailed financial comparisons should be made to choose among these options. This rule does not need to be followed if there is reliable corrosion data and effective monitoring systems<\/a>. For example, we might use different corrosion allowances for the upper and lower regions of a tall vertical vessel.<\/p>\n

Ensure that there's Adequate Drainage<\/strong><\/p>\n

Tanks and other storage containers should be designed in such a way that they can be easily drained and cleaned<\/a>. Therefore, all transitions should be smooth, and taps should be located so that the tank can be completely drained.<\/p>\n

Minimize Bi-Metallic Corrosion Cells<\/strong><\/p>\n

Avoid galvanic corrosion<\/a> by using similar metal throughout the structure, if possible, or by avoiding electrical contact by insulating different materials. (For background information, see An Introduction to the Galvanic Series: Galvanic Compatibility and Corrosion<\/a>.) Those components that are more prone to corrosion should be easily replaceable. Special parts (wasters<\/a>) can also be used to attract the corrosion, thus protecting other parts. To avoid crevice corrosion<\/a>, seals should be used and pressure should be adjusted on the gaskets<\/a> to prevent liquid penetration inside the crevices. In this way, it is possible to avoid the presence of stagnant water in the crevices and narrow gaps.<\/p>\n

Avoid Differential Aeration Cells<\/strong><\/p>\n

Differential aeration<\/a> should be avoided. For the components immersed in water, sufficient aeration should be ensured to cause passivation<\/a>, which slows the corrosion. Otherwise, aeration should be prevented as much as possible. Similarly, for the structures that are exposed to the atmosphere, easy drainage and an ample supply of air should be ensured, and vice versa for the porous surfaces<\/a> or structure having cavities—they should be properly sealed.<\/p>\n