What is tea staining, what effects does it have on stainless steel, and how can you prevent it?
Coastal corrosion or tea staining can take your stainless steel from shiny to brown tea stained and rusty looking over time and can it leave it looking a little worse for wear. Tea staining usually occurs within about five kilometers of the ocean and gets progressively worse the closer that you get to the sea. In the following article, we’re going to take a closer look at tea staining, what it is, what causes it, and ways that you can reduce tea staining on stainless steel components.
What Is Tea Staining?
Although tea staining looks unattractive, it’s not going to affect the structural integrity of the stainless steel. So, don’t panic immediately if you live in a coastal area and your new stainless steel starts to look discolored. Tea staining is simply a cosmetic issue.
Most cases of tea staining occur within about five kilometers of the ocean. As you get closer to the ocean, the tea staining on your stainless steel will usually get worse. However, there are also several environmental factors that you need to consider, including pollution, how sheltered the stainless steel is, wind exposure, local temperatures, and environmental impact.
While most tea staining occurs within about five kilometers of the ocean, you can also experience some tea staining effects up to twenty kilometers away from the ocean. Other factors which can cause tea staining on stainless steel include uncleaned welds, chemical fumes, and carbon steel contamination. All of these highlight the need for extreme care and diligence when you are fabricating any stainless steel components.
Why Does Tea Staining Occur?
It’s a complicated relationship between the contributing factors which cause tea staining. However, the closer you get to salty water, the more aggressive the tea staining can be. When you combine local conditions such as temperature, humidity, and the presence of corrosive substances such as salt on the surface of the stainless steel, they can be too aggressive for that grade of material.
What Factors Contribute to Tea Staining?
- Corrosive Substances – Sea salt on the surface of stainless steel is one of the most significant causes of tea staining. Sea salt causes the surface of the stainless steel to remain wet in high humidity environments for longer. Because of this, the stainless steel is wet and corroding longer than it regularly would be without the presence of salt.
- Atmospheric Conditions – When you combine atmospheric conditions with high humidity, such as in a tropical climate, the increased temperature can aggravate the tea staining and make it worse. The high humidity creates a layer of moisture on your stainless steel, which dissolves the salt and creates a corrosive pool on the surface of the metal. Lower humidity indoors and less salt means that tea staining is less common indoors.
- Design and Surface Orientation – If you have a poor design and don’t take into consideration factors such as drainage, textures that trap contaminants, and exposure to rainfall, the effects of tea staining can be worsened.
- Surface Texture – Any rough or uneven surface which can trap salt or moisture will be more susceptible to tea staining and corrosion. The smoother the surface, the more resistant to corrosion the stainless steel will be.
- Passive Surface Layer – To get the best corrosion resistance with any stainless steel fabrications, the passivation of the metal is vital. Any time that stainless steel is welded, the passive layer is removed. Restoring this passive layer is vital to prevent tea staining around welds.
- The Right Material – Believe it or not, but there are hundreds of different grade stainless steel varieties to choose from. However, only about ten are commonly used by fabricators. It’s the thin chromium oxide layer on the surface that gives the most corrosion resistance to stainless steel. Each grade of stainless steel has its own Pitting Resistance Equivalent. The higher the PRE, the more resistant to corrosion and tea staining the stainless steel will be.
- Regular Maintenance – Despite your belief, stainless steel isn’t 100% maintenance-free. However, simply rinsing off your stainless steel regularly with fresh water can help to remove any corrosives such as salt on the surface.
The Best Methods to Prevent Tea Staining and Removing Tea Staining
- Choose the right stainless steel for the job. The higher the PRE, the more resistant to tea staining and corrosion the metal will be.
- Consider your design and how that design will be once it has been fixed in situation. Try to avoid areas that will accumulate salt or pollutants, such as joints where water can pool for extended periods.
- Be careful during the engineering stage to avoid carbon steel contaminants. Pay close attention to bending, folding, and rolling machines used during the fabrication process and keep stainless steel material away from other material being cut or worked on.
- Clean any weld carefully. After the passive layer has been removed due to welding, passivation is vital. There are various high-quality electro passivation options to choose from, which will help protect any welded stainless steel joints.
- Electropolishing and electrochemical cleaning using a device such as the TIG Brush is an effective way to remove tea staining from stainless steel simply and quickly. You can also utilize aftermarket polishing creams and pads but be careful not to scratch or damage the surface of the stainless steel as it could make the tea staining worse over an extended period.
Before and After using the TIG Brush
What Is Tea Staining In Stainless Steel? – Conclusion
As you can see, there are a variety of different factors which all contribute to tea staining on stainless steel. Fortunately, while tea staining can make stainless steel look less attractive, it will not affect the structural integrity of the metal components.
If you have any questions about tea staining or would like to learn more, please don’t hesitate to reach out and contact us directly. Our friendly and professional team will be happy to assist you with your inquiries.