316 grade steel is often known as Marine Grade Stainless Steel and is one of the most common stainless steel on the market. It is an austenitic grade that has also 2-3% molybdenum, further enhancing corrosion resistance. 316 marine grade stainless steel is named as such because of its resistance to chloride corrosion when compared with other stainless steel grades.

Often grade 304 is positioned as a cheaper alternative to marine grade stainless steel, this blog post will outline some of the key comparisons between the two grades.

What is 304 Grade Stainless Steel?

304 is a highly versatile material that finds use in a range of outdoor applications such as automotive molding, wheel covers, trim, hose clamps, and kitchen appliances. It is resistant to moderately caustic or acidic solutions, meaning it works well for non-severe applications like food and kitchen environments. It is easy to use, clean, and comes in a range of finishes, adding to its popularity.

Grade 304 is, however, susceptible to corrosion from chloride solutions present in saline atmospheres. In such atmospheres, chloride ions can form localized areas of corrosion called pitting.

What is Marine Grade Stainless Steel?

There are many similarities been 304 grade and marine grade 316 stainless steel. The key difference between them is their composition, with marine grade stainless steel containing 2-3% molybdenum, which is an extremely hard metallic element that is used to toughen the material and enhance corrosion resistance.

Resistance to Corrosion

Corrosion is the name frequently attributed to the process of metal rusting. The process takes place when iron molecules combine with oxygen in the presence of water, forming a flaky red oxide.

Both iron and steel are extremely susceptible to this kind of corrosion, particularly when salt is present in their atmosphere, such as in coastal areas. 304 contains 18% chromium and 8% nickel while marine grade steel contains 16% chromium, 10% nickel, and 2% molybdenum. The high chromium content in chloride both metals means they are resistant to corrosion. 

Chromium reacts with oxygen, resulting in a small amount of oxidization. A thin film forms on the surface of stainless steel, adhering to the surface. This film forms an effective barrier against any additional oxidization and corrosion.

304 grade stainless steel is more susceptible to corrosion than marine grade steel due to its lack of molybdenum. Marine grade stainless steel is also more resistant to solutions that contain sulfuric acids, fatty acids, and bromides at high temperatures, frequently finding use in chemical processing applications.

Because marine grade stainless steel is non-reactive, it is used in the production of pharmaceuticals, as less contamination is likely to occur.

Is Marine Grade Stainless Steel Worth the Cost?

304 grade and marine grade stainless steel are very similar and both have many benefits. They’re versatile, easy to use and clean, and can be molded with ease. However, for applications close to the coast or other highly corrosive environments, marine grade stainless steel is far superior and will have an extended lifespan compared with 304 grade.

Masteel stocks both 304 grade and marine grade stainless steel, and our team of experts can advise you which grade would work best for your application. Get in touch today for more information.