Corrosion Resistant Aluminum Sheeting for Pontoon Boat
A pontoon boat is a flat boat that relies on pontoons to stay buoyant. These pontoons (also known as tubes) contain substantial reserves of buoyancy, allowing designers to create large deck with a variety of accommodations, including spacious lounge areas, standing bars and sun pads. A pontoon boat can have a draft of only 8 inches (20 centimeters), which reduces the risk of grounding and underwater damage, which allows it to load and unload cargo close to shore.
The pontoon boat made of 5083 aluminum armor plate can be used for decades without suffering any noticeable corrosion. The decommissioning of such ships is usually due to technical obsolescence rather than aging of the aluminum structure. As an Al-Mg alloy, 5083 aluminum alloy has excellent corrosion resistance and weldability, and can be used as the basic material for the manufacture of high-speed surface ships. Compared with steel, aluminum hulls and components are lighter in weight, higher in speed, and more fuel-efficient. It also has lower maintenance costs due to corrosion.
From the intergranular corrosion test, it can be seen that the alloying element affecting the weight loss per unit area of the 5083 alloy from large to small are Mn, Si, Zn, and Mg. The effect of Mn content on the mass loss per unit area of the alloy is significant, while the effects of other elements are relatively insignificant.
With the increase of Mn content, the mass loss of the 5083 alloy shows a trend of increasing first and then decreasing rapidly. When the Mn content is 0.75%, the mass loss of the alloy is the largest; with the increase of Zn content, the mass loss first decreases and then increases; with the increase of Mg content , the mass loss first decreases and then increases and then decreases again; as the Si content increases, the mass loss presents a trend of first increasing and then decreasing, and the mass loss is the largest when the Si content is 0.33%.
It can be inferred that in order to reduce the mass loss caused by intergranular corrosion of 5083 aluminum alloy, the Mn content should not be in the range of 0.5% to 0.75%, the Si content should not exceed 0.2%, and the Zn content should be controlled at 0.14 % or so, the Mg content is controlled at around 4.3%.
Studies have shown that Mn can make the 0(Mg5Al8) phase in the alloy precipitate uniformly, improve the intergranular corrosion resistance of the alloy, and reduce the harm of impurity Fe as a neutralizing element. When the Mn content is higher than 0.75%, the intergranular corrosion degree of the 5083 marine grade aluminum can be significantly improved. When the Mn content is 0.5% to 0.75%, the intergranular corrosion resistance of the 5083 aluminum is adversely affected.
Combining the test results of intergranular corrosion, exfoliation corrosion, and polarization curves, and through experimental verification, it is believed that the content of Mn is about 0.5%, the content of Si is not more than 0.2%, the content of Zn is controlled at about 0.14%, and the content of Mg is about 0.14%. When it is controlled at about 4.3%, and the rest is within the limit, 5083 corrosion resistant aluminum has good corrosion resistance.
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