The easiest way to realize anti-corrosion of metals without any special anti-corrosion measures is to use metals that are naturally corrosion resistant in particular environments. For this reason, this is used where there is no other way or the corrosion resistant metals can be applied at low costs. The actual implementations will require careful tests and evaluations in particular environments applied. Some examples are shown below.

(1) Low Alloy Steels

Typical steel is of carbon steel type, and when small amounts of Cu, Cr, Ni, or Mo are added to carbon steel it is called Low Alloy Steel. There are following examples.

Weather Resistant Steel

Steel alloy with small amounts of Cu or Cr added. When exposed in open air and rain, it forms highly corrosion resistant rust on the surface. This layer is formed over several years and no further corrosion will progress.

Sea Water Resistant Steel

Steel plates and pilings used for shoreline protection corrode from being splashed with sea water. To prevent this, steel alloys containing Cu, Ni, and P, or Cu, Cr, and P are typically used.

Sulfuric Acid Resistant Steel

This steel alloy is used for fuel burning power generation station boilers. It is designed to be resistant to sulfuric acid generated from sulfur included in the burning fuel. Alloys with Cu and Sb, Cu, Sb, and Sn added, and low alloys with Cr or Ni added to the former are used.

(2) Stainless Steels

Ferrite Family

A stainless steel alloy type with 12~13% Cr added. Forms a CrO surface layer that does not easily rust. There are SUS405 (Cr18%), SUS430 (Cr18%), SUS446 (Cr26%) and others.

Austenite Family

A stainless steel ally with Cr and Ni added to steel. Cr18%, Ni8% SUS304 is most commonly used.

Bi-polar Stainless Steel

A stainless steel alloy that is Cr and Ni contents adjusted to be 1/2 ferrite and 1/2 austenite.

SUS304L

A stainless steel alloy with carbon content less than 0.030% to overcome the weakness of SUS304 which is intercrystalline corrosion by chloride ions. Too much carbon contained causes forming of CrC, preventing forming of CrO, resulting in corrosions. This principle is also applied to SUS316L, SUS317L, and others.

SUS321、SUS347

A stainless steel with Ti (321) or Nb (347) added. These elements easily bond with carbon and form TiC or NbC, preventing formulation of CrC.