SS 1.4539 or UNS N08904 is an unstabilized, low-carbon austenitic stainless steel. It has high nickel (23-28%) and chromium (19-23%) content and contains additions of molybdenum (4–5%) and copper (1–2%). The chemical composition makes it highly resistant to corrosion, primarily in reducing acids like sulfuric and phosphoric acid. The steel is of high toughness, even at cryogenic temperatures, and possesses fair weldability and formability.

SS 1.4539 has some significant characteristics that make it fit for challenging uses:

Corrosion Resistance: Provides great resistance to regular corrosion, pitting, crevice corrosion, and stress corrosion cracking, especially in places with a lot of chloride.
Strength and Resistance: Offers a tensile strength of approximately 490 N/mm² and yield strength of 220 N/mm², guaranteeing long-lasting structural strength.
Weldability and Formability: Compatible with a variety of welding techniques and suitable for both cold and hot forming processes.
High-Temperature Resistance: Keeps its strength and resists rust even when it's very hot.

SS 1.4539 plates and sheets find extensive usage in industries that require strong anticorrosive protection.

Chemical Processing: - Utilized in reactors, tanks, pipes, and heat exchangers due to its ability to withstand aggressive chemicals.
Oil and Gas Industry: -Ideal for offshore platforms, subsea equipment, and pipelines that are exposed to marine environments.
Pharmaceutical Industry: -Applied in processing equipment where purity is very high and resistance to corrosive materials is needed.
Marine Applications: - Applied in seawater pipes, offshore machinery, and heat exchangers due to its excellent resistance to seawater corrosion.

In comparison to stainless steel grades such as 304 and 316, SS 1.4539 is more corrosion-resistant in environments with sulfuric and phosphoric acid. Although 304 and 316 are naturally popular, they may not perform as well in extremely corrosive environments. SS 1.4539 is utilized where long-term functionality and corrosion resistance are crucial.

SS 1.4539 UNS N08904 plates and sheets function well in conditions that lead to corrosion. They are required in chemical processing, oil and gas, pharmaceutical, and marine engineering industries. They are highly corrosion-resistant, strong, and possess many uses, which makes them reliable in adverse conditions.