So you have a project, and you want to use a familiar, readily available material. You know your decision boils down to 303 vs 304 vs 316 stainless steel. You want an end product of the best possible quality, but you have to watch costs. Using less expensive components lets you (if you choose) pass on savings to the end user.
Which type of stainless steel alloy is best?
Here are the facts about these three grades of stainless steel vying for your approval. Armed with a little data, you can save time selecting materials, not to mention skip the tension that results if you make a wrong material choice.
303 Vs. 304 Vs. 316 Stainless Steel
First off, what do 303, 304, and 316 stainless steels have in common?
A few things -- they resist corrosion and look great. They're also austenitic, so they're made with 15% to 30% chromium and 2% to 20% nickel content. As a result, they have good:
- Surface quality
- Wear resistance
- Impact resistance
For the most part, they're nonmagnetic. These factors help explain why these stainless steels, especially 304, are among the most-specified grades.
Despite all these similarities, the differences are still notable. The three grades work best in different applications -- like athletes playing different sports, they all have slightly different “skill sets.”
This fact alone can make up-front cost considerations less important than long-term cost-effectiveness. Simply put, 316 stainless costs more than 304 and, somewhat counterintuitively, 303 costs more than 304.
Where and Why Do 303, 304, & 316 Stainless Work Best?
The applications for 303, 304, and 316 stainless steel are not mutually exclusive. But there's a fair amount of crossover. They’re also each best suited for specific purposes or certain environments.
Here's a quick rundown on each alloy:
1. 303 Stainless Steel
This grade gets down to the nuts and bolts -- literally.
Besides chromium (minimum, 17%) and nickel (approximately 8%), it also contains at least 0.15% selenium or sulfur.
With these additional elements, 303 offers increased machinability. This alloy’s composition makes it ideal for corrosion-resistant, strong, long-lasting fasteners. It's also the choice for aircraft fittings and gears as well as bushings and other small components.
It's not as corrosion resistant as 304 stainless steel, but it still stands on its own. And its machinability at least partially makes up for the difference. Welding, however, doesn't work well with 303.
2. 304 Stainless Steel
Comprising 18% chromium and 8% nickel, type 304 stainless steel is sometimes referred to as 18/8.
This stainless steel alloy is pretty popular. Representing about half of all stainless steel products in the world, 304 is a workhorse. It boasts excellent corrosion resistance and it's weldable.
Of course, it's not perfect. In a high-chloride environment, such as near the ocean, it tends to pit. Otherwise, this steel is tough, strong, and lasts.
Applications for 304 stainless steel include places and products where beauty and/or cleanliness are important, such as:
- Kitchen appliances
- Heat exchangers
- Architectural projects
- Food processing plants
3. 316 Stainless Steel
This grade of stainless steel alloy is the most expensive. For good reason, too.
If your project involves a high-chloride environment, 303 and 304 stainless steel are probably not the best choices. But 316 is, and it’s a cost-effective, long-term investment.
What makes the difference? Molybdenum. Just a little, maybe 2% to 3% added to the mix, increases its corrosion resistance properties significantly.
This stainless steel should be considered for any project that might come into contact with chloride, including:
- Marine architecture
- Food processing systems
- Hot water systems
The Right Stainless Grade for the Right Place
When evaluating 303 vs. 304 vs. 316 stainless steel for your project, one of the best things you can do is to talk to your manufacturer about design-stage specifics, such as material choice. There’s nothing worse than finding out from a customer that your product didn’t work as it was supposed to because of an issue with its steel.
Like with any material selection, the key is to make the right choice for the application without making price the sole or even the most important consideration. In the long run, you and your customer will be happier with the finished product.
Here are some helpful charts for choosing the right metal for your project:
(This article was originally published in August 2018 and was recently updated)