So you’ve got a project in mind that requires the use of stainless steel. The question is what type do you need? Among the most common varieties are type 304 and type 316, but apart from 12 digits in the numerical scale what’s the difference. Let’s take a closer look.
The technical answer is that type 304 contains 18% chromium and 8% nickel while type 316 contains 16% chromium, 10% nickel and 2% molybdenum. In simplified terms it means that while type 304 is a versatile and durable metal for easier fabrication, it can succumb to rust when exposed to many types of chemical corrodents such as brine solutions, chlorides, bromides, and iodides.
Conversely with type 316 the key difference is the small amount of molybdenum. By adding just 2% it means that the metal now has a far greater resistance to chemical corrodent attack. So now you have a metal that’s still versatile, durable, and easy to fabricate, except it’s pretty much indestructible (within reason of course).
So what should each type of stainless steel be best used for?
Firstly there’s no visible difference between the two metal types. They are in fact polished and grained in exactly the same way. On smaller parts such as stainless steel clamps and feet items are sometimes marked with a circle and a No. 6 or 4 to indicate that it’s either type 304 or 316 grade steel. However larger parts or indeed sheets of metal aren’t. For this reason you should always have some kind of materials testing report to ascertain that you are in fact getting exactly what you’ve ordered.
Type 304 stainless steel is ideally used in a wide variety of scenarios, particularly where a corrosion resistant material is required, but not necessarily one that comes into direct contact with corrosive chemicals or elements. Therefore electrical enclosures, kitchen equipment including counter tops, wheel covers, storage tanks, pressure vessels, and piping are ideal items which can be made from type 304 steel.
Conversely any parts or items that come directly into contact with salt water or corrosive chemical products really need to be made using 316 stainless steel. It’s also known as marine grade steel for obvious reasons and therefore is best used on ships or other vessels that come directly into contact with salt water. This also includes any underwater pipework or equipment and is used in many industrial applications that come into contact with chemicals, such as storage vessels or tanks. In addition type 316 steel is the preferred metal of choice for many surgical instruments due to it’s non-reactive qualities.
Both types will provide a long service life if they’re used in the right conditions so you just need to make sure you know their final use before you make the final choice. If you’re still unsure about the difference between 304 and 316 grade stainless steel then you can always ask your local metal fabricator for advice.
At Metro Steel we’ve been fabricating steel for many years and have the skills and the experience to turn your ideas into products quickly and efficiently. Contact us on 07 3204 1000 today and put us to the test.