Why bother about corrosion and surface protection
Corrosion refers to the physico-chemical interaction between the metallic material and its environment. It is important to realise that this interaction can result in changes in the properties of the metal, and this may lead to significant impairments in its performance.
To avoid changes in the properties of the metal, one needs to be mindful about selecting the right surface protection material. This primarily depends on the presence and concentration of corrosion factors in the environment. After identifying the most relevant corrosion factors, it is recommended to take the guidance as defined by ISO 12944 on which surface protection method suits your environment best.
|Comparison||A2 grade||A4 grade|
|Material composition||18% chromium and 8% nickel content||>18% chromium, >8% nickel+ 3% of molybdenum content|
|Corrosion resistance||Limited resistance, only for areas with low and moderate pollution. The A2 grade is not recommended to be applied near salt-water, marine and coastal areas||Very high corrosion resistance. Even resistance in areas with high pollution and salt content|
|Resistance to chemicals||Not resistant to chemicals, and it can even react sensitively to ordinary household detergents||Resistant to aggressive chemicals|
|Cleaning||Recommended to be cleaned by clean water only. Chemicals and detergents can cause impairments in the functioning of the metal||Can be cleaned with both water as well as detergents with high chemical content|
|Hygiene||A2 grade is recommended for areas with low and moderate pollution and only ordinary hygiene requirements||For areas with high hygiene criteria, for example food production, the use of A4 grade is mandatory|
* Please consider the content of the table as guidance over explicit recommendation for a certain material or product
** According to ISO 12944
*** BUP (BIS UltraProtect 1.000) can be used depending on your environment. Please consult us for more information
Stainless Steel has become a popular choice of product over the years, primarily thanks to its high corrosion resistance and aesthetic appeal. The high corrosion resistance of the product is enabled by its high (over 11-12%) chromium content. Unlike regular carbon steel, when getting exposed to corrosive factors, the chromium layer of Stainless Steel starts oxidising instead of the steel itself. The oxidised chromium forms a very thin and tight layer which protects the metal from oxygen attacks. The corrosion resistance of Stainless Steel can further be enhanced by adding more nickel.
A2 vs A4 Stainless Steel
The two most commonly produced grades of Stainless Steel are 304 (also known as A2) and 316 (also known as A4). Even though they share a lot in common, there are some fundamental differences between the two. Please see table below for more guidance.
|Applications*||Corrosivity class**||Zinc coating||Hot dip galvanized||BUP (BIS UltraProtect 1000)||Stainless Steel|
|Dry indoor spaces||C1, C2|
|Indoor spaces with occasional condensation||C1, C2|
|Outdoor areas with low pollution||C2, C3|
|Outdoor areas with moderate pollution||C3, C4||***|
|Coastal areas||C4, C5, CX|
|Outdoor areas with heavy pollution||C4, C5, CX|
Please consult us for more information
The Walraven offer
With over 70 years of experience in the installation and surface protection market, we understand the complexity of selecting the right materials and assessing the corrosion factors in the field. To this end, next to various surface protection options, we offer a complete and fully A4 graded range of Stainless Steel product portfolio suitable for the most typical application areas.
With our customer-oriented logistics concept, we ensure prompt delivery, which can even happen within a week. Furthermore, upon request, we also support with the design, calculation and the prefabrication of the system.
Do you have questions relating to Stainless Steel or would like to get support with you next project?