What environmental factors should be considered when designing material selection?

This post was last edited by 2887848 on 2012-12-3 at 22:08. The reference answers provided by this site are: 1. Medium composition and concentration 2. Impurities 3. Temperature 4. pH value 5. Oxygen, oxidizing agents, and reducing agents 6. Water content 7. Flow rate 8. Corrosion products and films 9. Corrosion inhibitors 10. Operating and shutdown conditions 11. Surrounding and natural environment

Choosing materials appropriately is a meticulous and complex technique. It must take into account both the process conditions and possible changes that may occur during production, as well as the structure and properties of the material and any changes that might arise during its use. When selecting materials, the properties of the medium, temperature, and pressure are considered first. Whether the medium is oxidizing or reducing, and what its concentration is ； Are there any impurities present, and what are their properties? Do these impurities slow down corrosion or accelerate it? If they accelerate corrosion, what is the reason for that? In addition, it is necessary to fully understand the conductivity of the medium, its pH value, and the properties of the corrosion products formed. For example, stannic acid is an oxidizing acid; therefore, materials that can form a good oxide film in oxidizing media should be chosen, such as stainless steel, aluminum, tin, and other similar materials. Hydrochloric acid is a reducing acid, and the use of non-metallic materials offers unique advantages. The temperature and pressure of the medium are also important factors to consider. Generally, as the temperature rises, the corrosion rate increases; materials that are stable at high temperatures are usually also stable at normal temperatures. Materials that are stable at room temperature may not be stable at high temperatures. The higher the pressure, the greater the requirements for the material’s corrosion resistance, as well as the strength of the material required. Non-metallic materials, aluminum, cast iron, etc., often struggle to function under high-pressure conditions; in such cases, it is necessary to consider using other materials with higher strength or protective measures such as lining structures. When selecting materials, the purpose of the equipment, the manufacturing process, and its structural design characteristics must be taken into account. For example, pumps are fluid transfer machinery that require materials to have good casting properties and excellent wear resistance ； High-temperature furnaces require materials to have good heat resistance. When selecting materials, consideration should also be given to environmental corrosion of the materials and the specific requirements of the product. For example, in the pharmaceutical and food industries, toxic lead should not be used; instead, aluminum, stainless steel, zinc, enamel, and other non-metallic materials should be chosen. In addition to the factors that should be considered first as mentioned above, the properties of the material also need to be taken into account secondly. As structural materials, they generally require a certain degree of strength and ductility. For example, lead has low strength and cannot be used as a structural material; it is generally used only as a lining material. The quality of a material’s processing properties is often the key factor determining whether it can be used in production. For example, high-silicon cast iron exhibits good corrosion resistance in many media, but due to its hardness and brittleness, it is difficult to machine; therefore, only casting methods can be used, and the yield rate is low, which increases the cost of the equipment and limits its application. Furthermore, when selecting materials, one must also consider their price and source, adopting an economic perspective.

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Is the 2nd floor considered very high? This is not good.

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1. Atmospheric environment: temperature (extremely high, extremely low), average annual atmospheric pressure, humidity, etc. 2. Atmospheric medium: apart from nitrogen and oxygen, what about acidity and alkalinity? What is the air humidity level throughout the year? 3. Water resource conditions: What are the hardness and pH levels?

Choosing the right materials is very important; since there aren’t many anti-corrosion methods used in this type of work, this post can help one learn about them properly. :)

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