{"id":5566,"date":"2026-07-24T10:00:34","date_gmt":"2026-07-24T01:00:34","guid":{"rendered":"https:\/\/ohtavn.com\/?post_type=media&p=5566"},"modified":"2026-07-08T19:57:15","modified_gmt":"2026-07-08T10:57:15","slug":"correct-maintenance-method-for-stainless-steel-screws","status":"publish","type":"media","link":"https:\/\/ohtavn.com\/en\/media\/correct-maintenance-method-for-stainless-steel-screws\/","title":{"rendered":"Proper Maintenance Methods for Stainless Steel Screws and Tips for Extending Their Service Life"},"content":{"rendered":"
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Introduction<\/h3>\n<\/div>\n
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“It is stainless steel, so it should not rust”\u2014in manufacturing sites, this misconception ceaselessly invites unexpected troubles and increased costs. Certainly, Stainless Steel possesses excellent corrosion resistance, but in high-temperature, high-humidity environments like Vietnam, or under improper maintenance, corrosion and “galling” occur, directly linking to serious risks such as production line stoppages and product recalls. Particularly in the Vietnam market, where precision equipment and automotive parts manufacturing are accumulated, the reliability of fastening parts is a lifeline that determines the brand value of the final product.<\/p>\n<\/div>\n

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In this article, based on the specialized knowledge of fastening parts that Ohta Vietnam has cultivated over many years, we will scientifically reaffirm the characteristics of stainless steel screws and explain correct maintenance methods and secrets for extending service life that can be immediately practiced on-site. We present a concrete roadmap to realize significant reductions in procurement costs and downtime by reducing part replacement frequency through appropriate management. This series of knowledge should become a beneficial asset for all manufacturing industry stakeholders, from management layers to on-site technical personnel.<\/p>\n<\/div>\n

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The Mechanism of Stainless Steel Screw “Rusting” and Risks Specific to Vietnam<\/h3>\n<\/div>\n
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The Function and Limits of the Passive Film<\/h4>\n<\/div>\n
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First, let us share the technical basics. The reason stainless steel is hard to rust is that the contained chromium (Cr) bonds with oxygen to form a dense protective film called a “Passive Film” on the surface. The thickness of this film is merely 1 to 3 nanometers (1 nanometer is one-millionth of a millimeter), which is extremely thin, but it possesses a self-repairing function.<\/p>\n<\/div>\n

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However, this self-repairing function is not all-powerful. Even with SUS304 (18Cr-8Ni) defined by standards such as JIS G 4303, if iron powder adheres to the surface (“contact rust”) or in the presence of chloride ions (seawater or salty breeze), the film is destroyed, regeneration cannot keep up, and corrosion progresses. In particular, chlorine ions locally destroy the passive film and become the main cause of deep hole-like rust called Pitting Corrosion.<\/p>\n<\/div>\n

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Challenges in Vietnam’s Manufacturing Environment<\/h4>\n<\/div>\n
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Vietnam’s average humidity exceeds approximately 80% throughout the year, and can reach nearly 90% during the rainy season. This high humidity makes it easy for a moisture film to form on metal surfaces, promoting electrochemical corrosion reactions. Furthermore, accompanying rapid industrialization, the atmosphere in factory zones may contain sulfur oxides (SOx) and nitrogen oxides (NOx); these react with moisture to create an acidic environment, becoming factors that accelerate the corrosion of stainless steel screws.<\/p>\n<\/div>\n

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Even stainless steel screws that can be expected to have a durability of over 30 years in normal indoor environments may develop red rust in just a few months if maintenance is neglected under such environmental conditions. Therefore, rather than applying domestic Japanese standards as they are, the formulation of management standards adapted to the Vietnamese environment is indispensable.<\/p>\n<\/div>\n

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Prevention of the Fatal Trouble “Galling” and Torque Management<\/h3>\n<\/div>\n
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The Generation Mechanism of Galling<\/h4>\n<\/div>\n
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Along with rust, a frequent trouble with stainless steel screws is “galling” (seizing). This is a phenomenon where the screw threads expand due to frictional heat during tightening, and the metal contact surfaces weld together. Once galling occurs, it becomes impossible to remove or tighten the screw, and the bolt must be cut to be removed, resulting in massive man-hours for recovery.<\/p>\n<\/div>\n

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Stainless steel has the characteristics of low thermal conductivity (about one-third of carbon steel) and a large coefficient of thermal expansion (about 17.3\u00d710\u207b\u2076\/K for SUS304, approx. 11.7\u00d710\u207b\u2076\/K for carbon steel). In other words, frictional heat does not escape easily, and it expands easily with heat, so galling easily occurs if rapid tightening is performed.<\/p>\n<\/div>\n

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Utilization of Proper Torque and Lubricants<\/h4>\n<\/div>\n
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The best measures to prevent galling are appropriate torque management and lubrication.<\/p>\n<\/div>\n

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  1. Compliance with Proper Torque<\/strong>: Based on JIS B 1083 (General rules for tightening of threaded fasteners), set a torque coefficient (K-factor) matching the screw’s strength class and size. Generally, the torque coefficient for stainless steel screws is around 0.2 to 0.4, but it fluctuates greatly depending on the lubrication state. Rapid tightening with excessive torque using an impact wrench is strictly prohibited.<\/li>\n
  2. Use of Lubricants<\/strong>: By applying anti-seize agents containing molybdenum disulfide or fluororesin, the friction coefficient can be lowered to around 0.1. This makes it possible to dramatically reduce the risk of galling while stabilizing the Axial Force.<\/li>\n<\/ol>\n<\/div>\n
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    Best Practices for Maintenance and Selection to Realize Long Service Life<\/h3>\n<\/div>\n
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    Regular Cleaning and Environmental Improvement<\/h4>\n<\/div>\n
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    The most basic and effective maintenance to extend the life of stainless steel screws is “cleaning.” Simply by regularly washing off dust, salt content, iron powder, etc., adhering to the surface with water and drying it, the soundness of the passive film can be maintained.<\/p>\n<\/div>\n

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