Why use Stainless Steel fixings?
Stainless Steel has become a popular choice of product over the years, primarily thanks to its high corrosion resistance and aesthetic appeal. It is also very low maintenance and easy to clean making it suitable for applications where cleanliness and corrosion-resistance are key. For example, food and drink production plants, water treatment plants, pharmaceutical plants and so on.
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.
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.
| 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 |
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 EN ISO 14713 on which surface protection method suits your environment best.
| 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 | | | |
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| Outdoor areas with moderate pollution | C3, C4 | *** | |
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| Coastal areas | C4, C5, CX | |
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| Outdoor areas with heavy pollution | C4, C5, CX | |
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| Extreme/special applications | Please consult us for more information |
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* Please consider the content of the table as guidance over explicit recommendation for a certain material or product
** According to EN ISO 14713
*** BUP (BIS UltraProtect 1000) can be used depending on your environment. Please consult us for more information
The Walraven offer
With over 70 years of experience developing corrosion-resistant fixing products, we understand the complexity of selecting the right materials and assessing the corrosion factors in the field. We offer a number of different surface protections on our products from hot dipped galv to BIS UltraProtect to A4 graded Stainless Steel.
Alongside our products we have a Technical Support Service to provide advice and designs for your installation.
Watch our video for a quick overview….
Contact us
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