The use of stainless steel for the manufacture of various types of fasteners such as bolts, nuts and screws is common. Different environments and conditions require specific varieties of stainless steel, which are identified by a combination of letters and numbers. Designations such as A2 and A4 are commonly used classifications that indicate different compositions of materials and properties of the fasteners.
A4
Acid-resistant A4 is a corrosion-resistant option specially adapted for use in environments with high levels of salt or acid. These products are among the most durable on the market and are particularly well suited in areas close to the sea. Made of high-quality stainless steel, they are both acid and salt resistant.
A stainless steel A4 product is strong and can withstand high temperatures and is ideal for use in high humidity. This type has an impressive load capacity and is an excellent choice for industrial environments. It is easy to mount and requires no surface treatment.
A2
When choosing stainless material, it is important to strive for a balance between corrosion resistance, strength and cost. Type A2 stainless steel is suitable for use with most other stainless steel grades that have the same or lower corrosion resistance. It shows good resistance to moderate effects of corrosion, such as in non-coastal air environments, in fresh water, and in oxidizing acids (such as nitric acid) and organic acids (such as citric acid), as well as in many alkaline and saline solutions.
However, it is unsuitable for use against non-oxidizing acids (for example hydrochloric and sulfuric acid) and in environments with high chloride levels, such as brackish or salt water and salted winter roads. In environments with non-oxidizing acids, the protective passive film cannot be regenerated if damaged. Therefore, acid-resistant steel grades of A4 quality are required in such situations.
