Introduction
Stainless steel is durable, visually appealing, and resistant to corrosion, making it highly popular. But it can also rust due to various factors, including lack of maintenance and improper handling. This article highlights the causes of rust in stainless steel and provides 15 helpful ways to preserve stainless steel from rust or corrosion.
Top Causes of Rust in Stainless Steel
1. High Moisture / Humidity
Although stainless steel has good resistance against moisture, long-term exposure to environments with high moisture or humidity can make it susceptible to rust. This is because moisture gets trapped on the surface and causes corrosion over time.
2. Contamination
When stainless steel comes into contact with carbon steel or iron particles, it can become contaminated. This contamination leads to surface rust, present as localized spots on the stainless steel surface. With time it can become a serious corrosion if proper care is not taken.
3. Chloride Exposure
Chlorides, especially the ones in industrial chemicals and saltwater, are very harmful to the oxide layer that forms on and protects the stainless steel. It leads to pitting corrosion which is a localized one causing small holes in the metal. This type of corrosion can destroy the structural integrity of steel even if chloride is present in smaller amounts.
4. Strong Cleaning Agents
Strong cleaning agents with significant acid or alkaline quantity can destroy the protective layer of stainless steel which makes it more prone to rust. This can also negatively influence steel’s life span and performance due to structural and visual damage.
5. Physical Damage
Damage to the surface of the stainless steel in the form of dents, abrasions, and scratches can harm the chromium oxide layer. This makes it easier for the exposed steel to oxide and rust. It also destroys the visual appeal of steel.
6. Exposure to Chemicals
Chemicals with chlorine and other halogens can destroy the stainless steel’s oxide layer. Continued exposure to these chemicals can lead to corrosion, destroying the structural and visual look of steel. This makes steel unfit for usage.
7. Weld Decay
When stainless steel is not welded properly, weld decay takes place. This leads to the creation of chromium carbides on the boundaries. This process is called sensitization and it reduces steel’s resistance to corrosion. Weld decay leads to rust formation which in turn affects the stainless steel’s structure and strength.
8. Unsafe Storage
If stainless steel is stored in unsafe storage conditions such as contaminated or damp environments, surface rust can form due to the settlement of dust, moisture, and other contaminants. This can lead to rust and harm the stainless steel even before it is used.
9. Industrial Pollution
In industrial environments with significant air pollution, stainless steel comes into exposure to pollutants such as nitrogen oxides and sulfur dioxide. These pollutants take their place on the surface of stainless steel and react with moisture, accelerating corrosion and rust.
10. Lack of Cleanliness
When regular cleaning or maintenance of stainless steel does not take place, dust, chemicals, salt, and other contaminants can gather on the steel surface and trap moisture. This leads to rust formation as the protective layer is disrupted.
11. Gaps and Crevices
Tight spaces, gaps, and crevices in the structures of stainless steel can lead to the accumulation of moisture and corrosive materials that cause crevice corrosion. This corrosion harms the structure of stainless steel. It is only noticeable when significant harm has been done.
12. High Temperatures
Exposure to high temperatures makes stainless steel weak and more prone to oxidation and rust. This reduces its effectiveness and longevity.
13. Electrolytic Reactions
Electrolytic reactions cause galvanic corrosion that leads to serious damage to stainless steel. This happens when stainless steel comes in contact with a more electrochemically active metal (like carbon steel) in the presence of an electrolyte (water). This type of corrosion is due to the electron flow between two metals which causes rust on the less noble metal.
14. Design Flaws
Design flaws can cause early destruction of stainless steel structures by creating conditions that lead to rust. It can also cause localized corrosion.
15. Residual Stresses
During the manufacturing process, residual stresses may be left in stainless steel. This can lead to stress corrosion cracking which occurs when corrosion in the environment and tensile stresses cause the material to crack. This can lead to severe failure of stainless steel components.
15 Ways to Protect Stainless Steel from Rust
Although many factors can cause stainless steel to rust, many easy and simple preventive measures can preserve and protect stainless steel:
1. Frequent Maintenance and Cleaning
Regularly cleaning stainless steel prevents the accumulation of salt, dirt, and other contaminants that harm the protective layer. Using soft soap and water with careful rinsing and drying can preserve the integrity of stainless steel. Tough chemicals and rough cleaning materials should be avoided.
2. Proper Storage
Stainless steel should be stored in a dry and clean environment without moisture or contaminants. It should be packaged carefully to prevent moisture, dust, and dirt from covering the surface. Storing stainless steel materials vertically will further reduce the risk of contact with surfaces containing moisture.
3. Avoiding Exposure to Chloride
In environments where there is significant chloride, higher-grade stainless steel such as 316 would be better as it is more resistant to corrosion due to chloride. It would also be beneficial to apply a protective coating to save the surface from harm due to direct contact with chlorides.
4. Avoid Contact with Ferrous Metals
Since contact with carbon steel or iron can lead to contamination, specific tools and equipment for stainless steel should be used. Stainless steel should also be stored in a separate place from other ferrous metals to reduce risks of cross-contamination.
5. Design Planning
Stainless steel should be designed with fewer gaps and crevices so that corrosive elements or moisture cannot gather. Rounded edges instead of sharper edges also prevent the risk of localized corrosion or rust.
6. Protective Layers
Protective coatings like paint, polymer, and silicone provide an extra layer of safety against corrosive elements. These coatings are beneficial in tough environments, high humidity, and saltwater exposure. The coating should be frequently inspected and reapplied if required.
7. Electropolishing
Electropolishing, an electrochemical process, removes a thin layer of material and polishes the stainless steel surface. It reduces the irregularities in the surface to prevent corrosive agents from sticking to steel. It also improves stainless steel’s visual aesthetic and is beneficial for the hygiene and cleanliness of the components.
8. Passivation Treatment
Passivation, a chemical treatment, gets rid of surface contaminants and aids in the formation of chromium oxide layer on stainless steel. In this process, the stainless steel is immersed in an acid solution such as nitric or citric acid which gets rid of impurities like iron particles. Passivation treatment is recommended periodically for best resistance against corrosion.
9. Using the Right Cleaning Agents
Stainless steel has cleaning agents that are specifically made for it. These agents have a neutral pH and are non-abrasive. They ensure the protective layer remains intact. Chlorine-based cleaners or bleach should not be used as they can lead to corrosion and pitting.
10. Frequent Inspection and Maintenance
Stainless steel components should be regularly inspected, maintained, and cleaned. This includes carefully observing for any signs of damage, discoloration, and rust and addressing them promptly. Regularly maintaining stainless steel will prevent small problems from becoming a major issue and preserve the life and structure of stainless steel components.
11. Avoiding Exposure to Chemical
Minimizing stainless steel’s exposure to chemicals such as chlorine and other corrosive agents can prevent rust from forming. If it is exposed to chemicals, stainless steel should be promptly washed with clean water and dried to prevent the accumulation of residues that may cause corrosion.
12. Switching to Better Quality Stainless Steel
In tougher environments, standard steel grades may not work well. Higher-grade stainless steel like the duplex stainless steel may be more suitable. It has a higher corrosion resistance and is more suitable for challenging environments. Inoxicon sets high standard in choosing raw material supplier and our products have won the heart of more than 1000 clients from all over the world.
13. Maintaining Environmental Conditions
In highly humid and polluted environments, an optimum environmental condition should be maintained around stainless steel. This can be done by using dehumidifiers or air conditioners to lessen the levels of humidity. Efficient ventilation can also reduce pollutants. If stainless steel is outdoors, it should be protected from tough weather using enclosures or safety covers.
14. Using the Right Welding Techniques
To prevent weld decay, the right welding materials and techniques should be used. Low-carbon stainless steel grades like 304L or 316L should be used to reduce the risk of chromium carbide formation. Heat during welding should be controlled carefully and the weld area should be passivated after welding to reform the protective layer on the steel surface.
15. Cathodic Protection
This includes the use of a sacrificial anode. A sacrificial anode is a more reactive metal that corrodes instead of stainless steel. Sacrificial anodes should be inspected frequently and replaced when they corrode.
Conclusion
Although stainless steel is excellent for its corrosion and rust resistance, it requires proper care and preventive measures for longevity, functionality, and structural integrity. Understanding the factors that cause it to rust and the associated protective measures can ensure that stainless steel performs optimally for a long time.
The measures mentioned in this article are suitable for protecting stainless steel household appliances, industrial tools, or architectural elements. These will help you maximize the lifespan of your stainless steel.