Recently, many hardware processing customers have reached out to inquire about 201 stainless steel, which is prone to rusting and has made the cleaning process quite challenging. They are hoping for on-site technical support from Changlufeng Chemical. Our company has been specializing in precision cleaning technology for hardware for several years, and we frequently encounter and solve similar issues.
Why does 201 stainless steel rust after cleaning? And why do some pieces rust while others don’t? Let’s explore this together.
First, it's important to note that 201 stainless steel is more accurately classified as "stainless iron" due to its chemical composition, which differs significantly from standard stainless steels like 301 or 304. It contains much less chromium. Stainless steel relies on a thin, protective chromium oxide layer to prevent corrosion. However, this layer on 201 stainless steel is weaker. If the layer is damaged—whether during processing or cleaning—the underlying metal becomes exposed, leading to oxidation and rust.
Second, even if 201 stainless steel appears clean after washing, rust may develop later. This often happens due to improper rinsing. Many manufacturers focus only on removing visible oil and perform only one or two rinse cycles. If the surface looks clean, they assume the job is done. But in reality, residual alkaline components from the cleaner can remain on the surface. These residues may not cause immediate rust, but over time—usually within 3–10 days—they can break down the protective layer, leading to rust spots.
Third, if the cleaning agent contains acidic components, the protective film of 201 stainless steel may be compromised entirely. This can result in widespread rusting, either as a full sheet, partial areas, or temporary discoloration.
Fourth, even neutral cleaners can cause issues if not properly rinsed. Water-based cleaning agents contain organic compounds that can leave behind residues. These residues can absorb moisture from the air and react with airborne particles like sulfides or nitrides, creating an electrochemical environment that accelerates corrosion.
So, what kind of cleaner should you use, and how should the cleaning process be structured? Let’s take Changlufeng Chemical as an example.
We recommend avoiding strongly acidic cleaners, as they can damage the protective layer of 201 stainless steel. Alkaline cleaners are acceptable, but thorough rinsing is essential to remove any residue. Neutral cleaners are also a good option, as they are less likely to affect the material directly. However, even with neutral cleaners, proper rinsing is crucial to eliminate any leftover substances that could lead to future rusting.
In summary, choosing an alkaline or neutral cleaner is fine, but the key lies in the rinsing process. At a minimum, three thorough rinses are recommended. If possible, heated rinsing can improve effectiveness. Finally, drying the workpiece thoroughly is critical to prevent moisture from causing rust.
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