The Truth About Stainless Steel Corrosion: Dispelling Misconceptions
When rust spots or stains appear on the surface of stainless steel, many people are often surprised and question, "Isn't stainless steel supposed to be rust-resistant?" They may even suspect that the steel they purchased is of poor quality. This viewpoint, however, is a one-sided misunderstanding due to a lack of in-depth knowledge about stainless steel.
Reasons for Stainless Steel Screw Corrosion
Despite their strong corrosion resistance, high-temperature endurance, and decent rust prevention, stainless steel screws are not entirely immune to environmental influences. Under certain harsh conditions, stainless steel can still corrode. Here are several common causes of stainless steel corrosion:
Adhesion of Foreign Metal Particles
Stainless steel surfaces may accumulate dust or particles of other metal elements. In humid air, these particles and the stainless steel are connected by condensation water, forming a micro-battery that triggers electrochemical reactions. This reaction can damage the protective film on the stainless steel surface, leading to electrochemical corrosion.
Organic Matter Adhesion
When organic liquids (such as vegetable juice, soup, or phlegm) adhere to the stainless steel surface, they can form organic acids in the presence of water and oxygen. Over time, these organic acids can corrode the metal surface.
Contact with Acidic, Alkaline, or Saline Substances
If the stainless steel surface comes into contact with acidic, alkaline, or saline substances (e.g., alkali water from wall decoration or splashed lime water), local corrosion can occur.
Chemical Corrosion in Polluted Air
In air polluted with sulfur compounds, carbon dioxide, or nitrogen oxides, condensation water can form sulfuric acid, nitric acid, or acetic acid droplets, causing chemical corrosion.
Salt Spray Corrosion in Coastal Areas
In coastal regions, the high salt content in the air can lead to corrosion of stainless steel surfaces due to salt spray.
Improper On-site Storage
Poor storage conditions can lead to contamination by rust-prone materials or the presence of welding slag on the surface, both of which can cause stainless steel fasteners to rust.
How to Identify Genuine Stainless Steel
In the market, there are some quick methods to test the authenticity of stainless steel, such as using stainless steel reagent solutions or magnets. However, these methods have been proven unscientific over the years. The reasons include the complex composition of stainless steel reagent solutions, the lack of unified qualitative standards, and the varying experimental methods, making accurate judgments difficult.
Inaccuracy of Reagent Testing
Reagent testing is fraught with inaccuracies and lacks scientific basis. Different reagent compositions and experimental conditions can lead to varied results, making it an unreliable detection method.
Misconceptions about Magnet Testing
The use of magnets to test the authenticity of stainless steel has been repeatedly debunked as unscientific. The issue of magnetism in stainless steel has been thoroughly explained, and it is clear that simply using magnetism to distinguish the authenticity of stainless steel fasteners is unreliable.
Therefore, the most accurate and scientific method to verify the authenticity of stainless steel materials is through chemical element analysis. This method directly examines the material's composition, providing reliable identification results.
Summary
Stainless steel is not entirely "rust-proof," and its corrosion resistance is influenced by various factors. Understanding these factors can help us better prevent and address stainless steel corrosion. Moreover, scientific testing methods are key to identifying the authenticity of stainless steel. By using chemical element analysis, we can accurately determine the material's authenticity, avoiding unnecessary losses due to misconceptions.
