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Which is better for the roof, PPGI or PPGL?

Hi, I’m Ella Ma, the CEO of tytsteel.com. With more than 10 years of experience in OEM/ODM steel pipe, I’d love to share with you the valuable knowledge related to steel products from a Chinese supplier’s perspective. Hope you like this article, and please share it or subscribe to our newsletter.

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PPGI and PPGL sheets are two different kinds of color coated steel, which are widely used in various industries, for example, advertising, construction, transportation, appliance industry, etc. They are very similar. But there are still some differences.

So, what are the differences between PPGI and PPGL sheets? Keep reading for details.

Different Substrates

PPGI is short for pre-painted galvanized steel, while PPGL is short for pre-painted galvalume steel. As the name suggests, PPGI uses galvanized sheets (with a layer of zinc coating) as base metal. While PPGL is with galvalume sheet as substrate, which is coated with 55% aluminum, 43.3% zinc, and 1.6% silicon. This is the main difference between PPGI and PPGL, which will further influence their features and applications.

Service Life

As mentioned, both zinc coating and Al-Zn coating are used to protect the metal from rusting to prolong its service life. For the GI sheet, the base metal will be damaged when the zinc coating is all corroded. Generally, a galvanized sheet may last for 10 to 15 years. While aluminum and zinc alloy forms microscopic particle areas. The Zn-rich phase will corrode preferentially, while the Al-rich phase will corrode very slowly. So Al-Zn coating is more corrosion-resistant than zinc-coated steel sheet. According to data, the service life of PPGL is 3 times longer than that of PPGI. Below are some pictures for you.

Weight Difference

With the same coating thickness, Al-Zn coating is lighter than zinc coating. It is because the specific weight of aluminum is lower than that of zinc. That is to say, with the same weight, Al-Zn coating can cover 3% more space than the GI sheet.

Appearance Difference

The surface of the PPGL sheet is smoother than that of the PPGI sheet. It is because of the better adhesion of aluminum than zinc. For the same reason, PPGL sheets can be painted directly without pre-treatment. However, it is necessary to be pre-treated for galvanized sheets.

Different Features

The heat resistance of the PPGL sheet is better than that of the PPGI sheet. PPGL sheet can withstand temperatures of 315 ℃. Also, PPGL sheets have better corrosion resistance than PPGI. It is because that the dense layer made of aluminum can prevent the base metal from further eroding.

Price Difference

Due to the better performance and fewer qualified manufactures, the price of the PPGL sheet is 3%-11% higher than that of the PPGI sheet.

Which is better for the roof, PPGI or PPGL?

PPGL is more heat and corrosion resistant. Its service life is over 50 years under normal conditions. Whereas PPGI’s is about 20-30 years. But PPGL roofing sheets are more expensive than PPGI roofing sheets. This depends on your budget and the environment in which they are used.

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