Stainless steel is a group of iron-based metal containing at least 10% chromium (alloy metals).
The chromium oxide "CrO" creates an invisible barrier ("passive film") to oxygen and moisture.
The Chromium protects the iron against most corrosion or red-colored rust; thus the term “stainless” steel.
The layer is too thin to be visible, meaning the metal stays shiny. It is, however, impervious to water and air, protecting the metal beneath. When the surface is scratched this layer quickly reforms.
The purpose of stainless steel is to provide hard steel material highly resistant to stain, rust and corrosion.
There are over 150 grades of stainless steel, of which fifteen are most common. Type 304 is the most commonly used.
When it comes to types 304 vs 316, they are undistinguishable from each other. Although the grades may look the same, it comes down to the different elements. Lets look at the differences here:
304 is Diamond Spas most commonly used stainless steel as its one of the highest quality stainless steels and it welds beautifully. These are some of its characteristics:
-304 stainless steel contains 18% chromium and 8% nickel
- Great forming and welding properties
- Corrosion/ oxidation resistance thanks to the chromium content.
- Excellent toughness, even down to cryonegic temperatures which are defined as very low temperatures.
- Low temperature properties responding well to hardening by cold working.
- Ease of cleaning, ease of fabrication, beauty of appearance.
Commonly used in:
The food industry; for brewing, milk processing, wine making, as well as in pipelines, yeast pans, fermentation vats and storage tanks.
Type 316L stainless steel is more resistant to general corrosion and pitting than conventional nickel chromium stainless steels such as 302-304. It typically costs more but holds up it harsher environments. It has the following characteristics:
- 316 contains 16% chromium, 10% nickel and 2% molybdenum which prevents specific forms of corrosion.
- Withstand a higher load than other gauges for the same length of time.
- Excellent formability.
- Durable strength at high temperatures.
- Corrosion and pitting resistance.
- Proven to offer exceptional resistance in hard water areas.
- More resistant to solutions of sulfuric acid, chlorides, bromides, iodides and fatty acids at high temperatures.
Commonoly used in:
Construction of exhaust manifolds, furnace parts, heat exchangers, jet engine parts, pharmaceutical and photographic equipment, valve and pump parts, chemical processing equipment, tanks, evaporators, as well as pulp, paper and textile processing equipment and any parts exposed to marine environments such as stainless steel spas on yachts or boats.
So the question comes up of when you should use 304 versus 316. If you are planning on buying your hot tub for anywhere on the coasts, or humid enviroments, ask us about 316. Otherwise 304 is a ideal type for all other project locations.