Storage, Processing and Installation Guide for PPGI and PPGL Coated Coil

Prepainted galvanised and zinc-aluminium coated steel coil, known as PPGI and PPGL, is a finished building material rather than a raw substrate. Its service life is decided long before the roof or wall panel is fixed, by how the coating system is chosen for the environment, how the coil is stored, and how carefully it is formed and installed. The following guidance covers the points that most often determine whether a coated coil performs for its intended design life or fails early through avoidable damage.

Selecting the Coated Coil for the Environment

Selection starts from the atmosphere the finished panel will face, not from the price per tonne. The four broad categories are rural, urban, industrial and marine atmosphere, and each imposes a different corrosion load. The relatively enclosed internal environment of a building also matters, because trapped moisture or chemical vapour attacks the reverse side of the sheet as well as the coated face. The organic coating system is specified under EN 10169, the metallic coating under EN 10346, and prepainted metallic-coated sheet for building use under ASTM A755/A755M, so the coating mass class, for example a Z275 zinc designation, and the paint system should be recorded on the order.

Identify the specific exposure conditions of the site: acid, alkali, salt, humidity, sunlight and ventilation.

Match the coating system to those conditions, and write both the metallic coating mass and the organic coating type into the specification.

Confirm the intended service life so that substrate and coating are selected for the same target, rather than over-specifying one and under-specifying the other.

Storage and Transport Rules

Store PPGI and PPGL coil in a dry, ventilated place, away from acids, alkalis, salts, organic solvents and other corrosive media.

Protect the coil during transport and handling from rain, snow and mist, which cause surface rust, and from paint film damage, contamination, collision and squeezing.

Keep the coil in its original factory packaging and in its original wound state; the packaging should not be opened at will before processing.

Use lifting equipment that does not damage the coil edge or the outer wraps, and avoid dragging coils across each other.

Processing and Installation Rules

For one project, follow the principle of using products from the same manufacturer and the same batch, so that colour difference between panels does not spoil the appearance.

Avoid low-temperature processing. Forming and profiling should be carried out above about 7 degrees Celsius, because the coating becomes brittle when cold and is more likely to crack.

Select tooling suited to coated material and check surface quality and coating adhesion during processing; if an abnormality appears, stop and identify the cause before continuing.

Prevent damage to the protective coating: keep cut metal particles from hot cutting off the surface, avoid sliding and collision between stacked profiled sheets, avoid dragging tools across the coating and avoid walking on panels in hard-soled footwear.

Seal fixing bolts with waterproof and anti-corrosion material so that fasteners do not become the starting point for corrosion.

If the coating is damaged during processing or installation, apply a compatible repair coating promptly to preserve the service life of the sheet.

Post-Installation Care, Roof Slope and UV Exposure

After the profiled sheets are installed, keep the sheet surface and the cut edges clean and free from corrosive media such as cement, acid, alkali and salt. Where the coil is used for roofing, the installation slope should not be less than 10 degrees so that rainwater drains freely and does not pond on the panels, because standing water is one of the main causes of premature corrosion at joints and fasteners. Long-term direct sunlight and other ultraviolet exposure should be avoided during transport, storage, processing and installation of coil with an epoxy backing coat, since the backing layer is not formulated as a weather face. Regular cleaning of the finished surface, without abrasive tools, preserves both appearance and coating integrity.

Checks on Delivery and During Processing

Inspect each coil on arrival for wrapping damage, edge deformation, moisture and any visible coating defect, and record the batch number against the delivery documents. Where an appearance or quality abnormality is found, processing should be suspended and the deviation raised with the supplier before the material is used, because a defect that is built into a finished roof is far more expensive to correct than a coil that is queried on the yard. During processing and use, monitor surface condition and coating adhesion, and store the tested samples with the batch records so that performance can be traced later.

Frequently Asked Questions

Q: What decides which PPGI or PPGL coil should be selected?
The external atmosphere of the site, whether rural, urban, industrial or marine, together with the enclosed internal environment and the specific exposure to acid, alkali, salt, humidity, sunlight and ventilation.

Q: Why should coated coil be formed above about 7 degrees Celsius?
At low temperature the organic coating becomes less flexible, so bending and profiling can crack the film. Working above roughly 7 degrees Celsius keeps the coating ductile enough for forming without damage.

Q: Why must panels for one project come from the same batch?
Coating colour can vary slightly between production batches, and mixing batches on one elevation makes that difference visible. Using one manufacturer and one batch keeps the colour consistent.

Q: How should a damaged coating be treated on site?
Minor damage should be repaired promptly with a compatible repair coating, and cut edges and drilled holes should be treated in the same way, so that the substrate is not left exposed to the atmosphere.

Q: What roof slope is recommended for coated steel sheet?
A slope of not less than 10 degrees is recommended, so that water drains freely and does not stand on the panels, since ponding accelerates corrosion around joints and fasteners.

Q: How should coated steel coil be stored before installation?
In a dry and ventilated place, away from acids, alkalis, salts and organic solvents, in the original factory packaging and wound state, protected from rain, snow and mist throughout transport and handling.