Analysis Of Corrosion Phenomena in Stainless Steel Nuts

The quality of a 304 or 316 stainless steel nut is directly related to the overall quality of the equipment. As an indispensable component in equipment assembly, stainless steel nuts can be said to be the foundation of product connection structures. The production of stainless steel nuts involves multiple links such as material selection, mold design, and production processes. Every time we see batches of 304 and 316 stainless steel nuts rolling off the workshop production line, being packaged and shipped, a sense of pride arises spontaneously, making us completely oblivious to the monotony of this industry.

When stainless steel nuts are stored in the atmosphere for a long time, rust may occur once the material's corrosion resistance lifespan reaches its limit. If the corrosion of stainless steel nuts is severe, it will damage the internal threads, making disassembly extremely difficult later. In extreme cases, it may even cause the nut and bolt to seize (galling), bringing great inconvenience to maintenance and replacement.

Once corrosion-induced seizing occurs, the time cost of removing a single stainless steel nut is extremely high. Sometimes, a small nut that cannot be replaced in a timely manner may lead to delays in delivering large orders worth tens of millions of yuan. After long-term analysis, the corrosion of stainless steel nuts is mainly divided into three types:

The first is material-induced corrosion. This type of corrosion is mainly caused by the material itself, such as insufficient material purity or the presence of impurities, which affect the corrosion resistance.

The second is local cross-sectional corrosion. This type of corrosion usually develops gradually during later installation and use, with complex causes. It may be due to harsh service environments (such as high salt spray, high humidity) or chemical corrosion caused by strong acidic substances dripping onto the nut surface.

The third is general corrosion, which is the most severe type. When general corrosion occurs, the nut should be replaced promptly first, and then the corroded sample should undergo in-depth testing to verify whether the material meets the standards. Most of these cases involve the use of inferior materials posing as stainless steel, which is a serious issue-consideration should be given to replacing the original supplier.

High-temperature environments will accelerate the corrosion of stainless steel nuts. Long-term exposure to such environments will seriously affect the performance of the nuts, so this situation should be avoided as much as possible. When carbon steel nuts corrode at high temperatures, the appearance changes are obvious and easy to detect; however, the corrosion of stainless steel nuts at high temperatures is mostly internal or local slight corrosion, which is difficult to perceive from the appearance and has strong concealment.

Therefore, we must select qualified stainless steel nut products. In the process of structural design, installation, and use, we should try to avoid corrosion caused by nut quality issues. Many enterprises neglect the management of stainless steel nut storage to save costs and pay no attention to corrosion points found during use. For the convenience of delivery, they even adopt secondary cleaning and polishing methods to make the nut surface look brand new. However, internal corrosion has already damaged the core performance of the nuts, laying hidden safety hazards.

When unqualified stainless steel nuts enter the production line, operators can hardly judge their quality with the naked eye and will only install them directly as qualified products. Such nuts with corrosion hazards are also particularly prone to seizing during installation. We have emphasized the seizing problem of stainless steel fasteners countless times-the reason for repeating this is that there is currently no way to completely eliminate the seizing of stainless steel bolts and nuts. If such problematic nuts are used, the probability of seizing will increase significantly.

Even if more attention is paid during later installation, such as adding spring washers or adjusting torque wrench parameters, it will be difficult to avoid seizing. Because after corrosion occurs, the threads will undergo a deterioration process, resulting in imperceptible deformation to the naked eye. In addition, corrosion points are likely to leave impurities in the thread gaps, which will further increase the risk of seizing.