Most of us understand stainless steel in our day-to-day lives as a metal that doesn’t rust or stain at all. When exposed to water, it can last indefinitely without losing its strength or durability—or its aesthetically appealing luster. Unfortunately, you’ve probably seen just enough rust on stainless steel products in your lifetime to know that rather than “stainless,” a more accurate term for stainless steel might be “stain-resistant.”
So, as a project manager in charge of procurement, you might find yourself wondering: If stainless steel can still rust and stain, is it really safe to use it to build water lines and commercial or industrial water handling systems? Yes—as long as you know how to choose the right type of stainless steel.
At American Stainless, we know stainless steel like the backs of our hands—it’s in our name, after all. In this blog post, we’ll put that expertise to good use to explain how stainless steel reacts to water, as well as how to choose the right grade of stainless steel for water transport systems.
Can stainless steel go in water?
Stainless steel pipe, structural tubing, and other pipeline and process line components can withstand immersion in water. In fact, stainless steel’s water resistance is excellent compared to other metals. However, there are limits to the tolerance of stainless steel.
Stainless steel is highly resistant to moisture, water, and other corrosive chemicals. The secret to its success is a thin, self-healing barrier layer on its surface composed of chromium oxide. This barrier layer is created when oxygen in the air around the steel bonds with chromium in the steel, protecting the iron in the steel from rusting. As a result, stainless steel pipe and tube can maintain their structural integrity for a long time in wet environments.
But being resistant to chemical corrosion or rusting is not the same as being immune. Stainless steel’s chromium oxide layer can still reach the limit of its protective capabilities if it’s exposed to too much water for too long. When that limit is exceeded, the iron within the steel will start to bond with and react to the oxygen in the air and water—and that means rust, which weakens the steel’s structural integrity and exposes your pipe systems to risks of leaks, bursts, and other failures.
So, yes, stainless steel can go in water and stay there for a much longer time compared to steel or iron. In water lines and treatment systems, stainless steel pipe and tube can last longer with reduced maintenance requirements—but it still needs to be regularly inspected and maintained to prevent water damage from taking its toll.
Ranking the Best (and Worst) Stainless Steel for Water Pipes
Industries using steel tubing pay close attention to the type of steel they use. Different types of steel can be more or less chemical-resistant and water-resistant, or more or less capable of functioning under extreme temperatures and pressures. The right steel for the job lasts longer, minimizes risks of emergency maintenance and repairs, and keeps pipe systems functioning at maximum efficiency.
Stainless steel isn’t just one type of steel, but rather a category in its own right. Different grades of stainless steel have different ratios of iron to chromium, nickel, and other elements that affect their water resistance, among other physical properties like their resistance to harsh chemicals and acids.
When you use stainless steel in water handling systems, you need to be careful to use the right type of stainless steel for your environment. The more exposed to water your pipe and tube are, the more important it is to choose a more water-resistant grade.
Excellent Water Resistance: Grades 316 and 316L
Thanks to the addition of molybdenum, Grade 316 and Grade 316L stainless steel is excellent for water pipes—and not just freshwater. Marine vessels and industrial desalination plants can trust Grade 316/L stainless steel to stand up against heavy exposure to seawater and brine, which can be much more corrosive.
Great Water Resistance: Grades 304 and 304L
These are the most widely used stainless steels due to their high strength and easy workability, but their resistance to water is reduced compared to 316/L stainless steel. You can use this stainless steel for water lines, as well as food or beverage processing lines, but avoid using it in marine environments.
Good Water Resistance: Grade 303
303 stainless steel is similar to 304 in its chemical composition, but with added sulfur, which makes it easier to fabricate into complex configurations for a wide range of pipe and tubing applications. However, the trade-off is reduced corrosion resistance, which makes it less suitable for long-term water exposure than 316/L and 304/L stainless steel.
Decent Water Resistance: Grade 430
As a ferritic stainless steel, 430 is less resistant to corrosion than austenitic grades like 304 and 316. It is not recommended for chlorine-rich environments, but is adequate for less demanding water applications where high cost is a consideration.
Poor Water Resistance: Grades 409 and 410
If you plan on using stainless steel for water transport systems, you won’t want to use these grades. Their limited corrosion resistance makes them more suitable for industrial environments where water exposure is minimal.
Choosing the Right Stainless Steel is Easy With American Stainless
Across the US Southeast, industries using steel tubing and pipe turn to American Stainless as their go-to supplier. With a vast network of domestic and global pipe and tube manufacturers and quick turnaround on shipping, purchasing and project managers trust us to deliver the pipe and tube they need, fast.
Quality products and fast delivery are important for any pipe and tube supplier, but sometimes you need help deciding what products your application demands first. When you have questions about choosing the right type of pipe to meet your project specs, our customer service team delivers speedy, straightforward answers so you can make snap procurement decisions with confidence. Not sure how to select the right stainless steel for water pipes or marine systems? Just get in touch with us and ask.