PPGI vs PPGL sheet in PUF panels, and which sheet thickness to choose

What do PPGI and PPGL mean?

PPGI

Pre-painted galvanised iron: a steel sheet hot-dip coated with zinc, then primed and painted on a coil line. The zinc protects the steel by corroding first, sacrificially, at scratches and cut edges.

PPGL

Pre-painted galvalume: a steel sheet hot-dip coated with an aluminium-zinc alloy (about 55% aluminium), then painted. The aluminium forms a tough barrier layer, and the zinc still gives some sacrificial protection at edges.

In a PUF panel the skins are the weather face outside and the hygienic face inside. The foam does the insulating; the skins decide how long the panel keeps looking and performing like new.

PPGI vs PPGL: how do they compare?

For most outside faces in India, PPGL is the safer default. PPGI remains common for inside faces and for buildings in dry inland climates where cost is the main concern.

What do the 0.3, 0.35, 0.4 and 0.5 mm columns mean?

Price lists show one rate for each sheet thickness, for example 0.3/0.3 mm or 0.5/0.5 mm, meaning the thickness of the outer and inner skin. Our price board lists four columns of PPGL on both faces; the same core with thicker skins costs more because the panel contains more steel.

You can also mix skins, for example 0.5 mm outside and 0.4 mm inside, where a maker offers it. See every thickness and sheet column priced on pages such as the 80 mm wall panel and the 50 mm roof panel.

Does the paint on the sheet matter?

Yes. The metallic coating protects the steel; the paint protects the coating and gives the colour. Most panel skins carry a polyester paint system on the outer face, which is the common standard for roofs and walls in India. Silicone-modified polyester and PVDF systems typically hold their colour and gloss longer in strong sun, and cost more.

The inner face of a cold room or food room usually needs a light, smooth, easy-to-clean finish suitable for food contact areas, and some makers offer a specific hygienic or food-safe coating. Ask the maker which paint system is on each face, the paint thickness, and whether the colour is the same batch for the whole order; colour can vary slightly between coil batches.

Light colours reflect more sunlight than dark ones, so a white or off-white outer face on a roof stays cooler in the sun and puts less heat load on the PUF core. Dark colours fade more visibly over the years and run hotter on the surface.

When is the thicker or better-coated sheet worth paying for?

• Coastal and humid sites (within a few kilometres of the sea, or near ponds and wash areas): choose PPGL with a good paint system, and seal every cut edge.
• Cold rooms and processing rooms washed down often: choose a food-safe inside finish and at least 0.4 mm on faces that trolleys and crates can hit.
• Roofs walked on during installation and maintenance: thicker outer skins dent less under feet.
• Chemical or ammonia exposure: ask the maker for a specific paint system or stainless steel faces; standard paint may not suit.
• Dry inland cabins and partitions: 0.3–0.35 mm PPGI or PPGL is common and keeps the rate down.