What is the difference between T1 and T2 in ASTM A463? Can T1 replace T2?
Firstly, let's take a look at the past and present of the continuous hot-dip galvanizing process
From 1930 to 1931, the Sengemir process was born, and the emergence of the continuous hot-dip galvanizing process marked the beginning of the era of large-scale industrial production of coated steel. In 1939-1940, based on the Sengemir method, the American company Amco developed aluminum plated steel plates. However, for over 50 years, aluminum plated steel plates were not widely used due to their poor processing performance, where molten aluminum quickly formed Fe AI based metal compounds upon contact with the steel base.This alloy was hard and brittle, which would seriously affect the plastic formability of aluminum plated steel plates! In 1999, ArcelorMittal successfully developed aluminum silicon steel plates, which solved the above-mentioned defects by adding a certain proportion of silicon to the coating, further improving the processing, heat resistance, and corrosion resistance of the steel plates.
In 2006, the ASTM A463 standard was introduced, and Type 1 aluminum silicon alloy coatings and Type 2 pure aluminum coatings were officially introduced.
T1 coating is usually 80-150 grams per square meter, with a silicon content in the range of 5-11%. Pure aluminum coating T2 has a minimum value of 200 grams per square meter in this standard! Currently, there are approximately 12 global manufacturers of aluminum coated steel plates, with the vast majority producing T1 standards. The latest survey has found that there may not be more than two companies that can produce T2 standards, or even only one... Moreover, due to the small number of orders, it is difficult to organize production, the delivery time is very unstable, and the price seriously exceeds the market's acceptance capacity! This has led to an increasing number of projects replacing T2 with T1.
Can T1 replace T2? Is this operation scientific? Next, we will analyze three aspects of metal protection:
1. Weather resistance:
Strictly speaking, aluminum forms aluminum oxide during the oxidation process, while silicon forms silicon oxide. The stability of aluminum oxide is slightly better than that of silicon oxide, but if the chemical bond between the two is to be broken, it must reach at least 1700 ° C and 2050 ° C. Therefore, in general application scenarios, there is no significant difference in weather resistance between the two, as the energy required to destroy Al-O and Si-O is too large! If we have to make a comparison, T1 is slightly weaker than T2 in this regard.
2. Chemical resistance:
Because aluminum is a reactive metal and silicon is a non-metal, aluminum silicon coated steel plates have better chemical resistance than pure aluminum coatings in acidic and alkaline environments. Therefore, in this regard, T1 is significantly better than T2!
3. Mechanical resistance:
Due to the presence of silicon, the aluminum silicon coating not only does not form a rich Fe Al hardening layer on the surface of the steel substrate, giving the aluminum silicon steel plate better processability, but also makes the alloy coating slightly harder than pure aluminum coating. Therefore, in this regard, T1 is significantly better than T2!
In practical applications, weather resistance is quite complex and often involves more than just oxidation or high temperature environments.
There may be some acidity or alkalinity present. Therefore, we believe that as long as the coating thickness of T1 is increased to meet the standard of T2, T1 can replace T2 in many industries such as petrochemicals and new energy. However, T2 may not necessarily replace T1 because the formability of T2 processing is the core factor limiting its development, which is also why T1 has experienced rapid growth in demand in recent years. Users can confidently use T1 products.
The above is the conclusion drawn by our company based on industry characteristics, material characteristics, element properties
And other aspects after consulting and researching various manufacturers and consulting a large amount of literature! And we boldly predict that pure aluminum T2 coating may be discontinued and eventually disappear due to its very high price, difficulty in organizing orders, long delivery time, and other factors. The above information is for reference only!
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