World over people have tried many materials to manufacture grain storage silos but eventually they could understand that all materials are not suitable for fabricating Grain Storage silos. Some are expensive and unviable and some have durability and strength related issues. Finally, the following metal coated steels are universally accepted to construct grain storage silo.
GI Steel, which has metal coating of 99.7% Zinc + 0.2% Aluminium over mild steel which is carried out at 450 Deg C
Galfan Steel has alloy coating of 95% Zinc + 5% Aluminium
Zincalume Steel has alloy coating of 55% aluminium, 43.4% zinc and 1.6% silicon which is carried out at 600 Deg C.
And, MAGNELIS Steel has coated with alloy of 93.5% Zinc + 3.5% Aluminium + 3% Manganese
In India, Food Corporation of India for its Grain Silo projects has specified minimum acceptable criteria of Silo Sheet as GI Steel of 350 gsm which is actually designated as GI-115 Z-350 having coating thickness 25 microns. However, in Corrigendum 1 of Tender ID: 2018_FCI_336318_1 (RFP Reference No: Silos/279/DBFOO/6 locations), Food Corporation of India has clarified, while answering Query (Refer Sr No. 9) that the developer is allowed to design and select specification & material for sheet metal silo bins to achieve the output parameters and services level indicators. This means that developers are free to choose any material for silo which can fulfil the minimum service life criteria of 30 years. Henceforth developers started experimenting with various grades of Metal Coated steels of GI, Galfan, Zincalume and Magnelis so that they get maintenance free silos with service life much more than 30 years.
Grain silos are outdoor equipment and hence exposed to harsh environmental corrosion. All metal coated steels have capabilities to withstand environmental corrosion. These capabilities are measured by conducting accelerated corrosion test which is known as Salt Spray Test. The results of Accelerated Salt Spray Tests exhibit how a metal coated steel will perform against environmental corrosion.
Performance of various metal coated steels on Accelerated Salt Spray Tests is shown in tabular form below which shows that Magnelis is far superior than any other Metal Coated steel to resist environmental corrosion. Hence Magnelis is most suitable material for Grain Silo Manufacturing.
Advantages of Magnelis Steel
Magnelis® is a wonder steel with a protective alloy coating of 93.5% Zinc + 3.5% Aluminium + 3% Manganese. Magnelis steel has various benefits in comparison to other metal coated steels as mentioned below.
Magnelis is a most cost-effective alternative to stainless steel and aluminium.
Magnelis is always recommended for applications where the risk of corrosion is higher than usual, such as in areas exposed to chlorides and ammonia. Hence it is best suited for environmental corrosion.
Magnelis® forms a very dense impermeable zinc magnesium based protective film, unlike galvanised steel where the film is very porous. Hence it is almost impossible for the environment to penetrate this film and this makes Magnelis a long lasting material.
Even the primary Magnelis grade which is ZM 120 outperform GI – Z640, Galfan ZA-275, Zincalume (or Aluzinc) AZ-150 grade.
Besides, Magnelis has exceptional corrosion resistance to soil, which is 3.8 times more as compared to galvanised steels.
The extended durability of Magnelis® results in reduced maintenance and saves a lot of money as it eliminates need for post painting of sheets.
Magnelis is a self-healing steel which means that if the material is scratched, a chemical reaction will automatically create a protective layer over the scratched portion and protects it from further corrosion.
The picture below is self explanatory and shows the superiority of Magnelis Steel