news — from the mill.
Production notes, industry updates, and a little colour on what we’re making this month.
PPGI Coil Oil Canning and Ridging Prevention
Oil canning and ridging in PPGI roofing can be reduced, but rarely eliminated, by controlling four variables together: the flatness and residual stress of the incoming coil, the panel geometry and rib pattern, the roll-forming setup, and how the sheets are stored, handled and fixed on site. The most reliable prevention strategy is to treat […]
Read →GI Substrate Surface Quality for PPGI Spangle and Skin Pass
For a smooth, defect-free prepainted finish, the GI substrate characteristics that matter most are spangle size and uniformity, surface profile (roughness), skin-pass condition, surface cleanliness, and flatness. Spangle is the visible zinc crystal pattern formed during hot-dip galvanizing; if it is coarse or uneven, its relief can telegraph through thin paint films as a mottled […]
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Galvalume Substrate for PPGI: Benefits and Limitations
Using a Galvalume (GL) substrate instead of a galvanized (GI) substrate for prepainted steel gives you better cut-edge and scribe corrosion resistance in many atmospheres, higher heat reflectivity, and often a longer time to first red rust on sheared edges — but it also brings harder forming behaviour, edge-creep paint undercutting risks, tighter coil-handling requirements, […]
Read →PPGL vs PPGI Cut Edge Corrosion Resistance
The cut edge of PPGL usually corrodes differently from PPGI because the two products carry different metallic coatings under the paint: PPGI is built on a zinc coating, while PPGL is built on an aluminium-zinc coating (commonly called Galvalume). Zinc protects a cut edge mainly by sacrificial action — it corrodes preferentially and, in effect, […]
Read →PPGI for Roofing: Oil Canning vs Ridging Causes
Oil canning and ridging are two different cosmetic defects that appear on prepainted galvanized (PPGI) roofing sheets, and they have different causes. Oil canning is local, wavy elastic buckling of a flat area between ribs or stiffeners, driven mainly by low bending stiffness, wide flat widths, thin gauge and installation stress. Ridging is a directional, […]
Read →PPGI Export Packaging Standards for Seaworthy Shipments
The standard packaging requirement for exporting PPGI coils to prevent sea freight damage is a layered, seaworthy pack that keeps moisture away from the coil, holds the coil rigid inside the container, and survives multiple handlings between the coating line and the buyer’s decoiler. In practice that means an inner wrap, a metallic or heavy-duty […]
Read →PPGI Coil Edge Damage: How to Inspect, Document, and File a Claim
If your PPGI coil arrives with edge damage, the correct sequence is: stop unloading or further handling, photograph and video the coil in place before anything is moved, record the damage on the delivery receipt or carrier document, notify the supplier and freight forwarder in writing within the notice period stated in your contract, and […]
Read →PPGI Pencil Hardness Test: A Quick Check for Coating Durability
The pencil hardness test on PPGI (prepainted galvanized iron) is performed by drawing pencils of increasing hardness across the cured paint film at a fixed angle and load, then inspecting the coating for scratches or film removal to identify the hardest pencil that does not damage it. The result is reported as a grade on […]
Read →PPGI T-Bend Test Explained for Coil Buyers
A T-bend rating tells you the tightest 180° fold a prepainted galvanized (PPGI) test strip can survive without the paint coating cracking or flaking, expressed as a multiple of sheet thickness: 0T is a fold with no gap, 1T folds the strip back on itself with one thickness of material in the bend, 2T leaves […]
Read →PPGI Color Fade Warranty: What to Expect
A realistic PPGI color fade warranty is usually a limited, pro-rata or stepped guarantee against excessive chalking and color change on the painted face of the coil, typically measured against a defined standard and expressed in years from delivery or installation — not a promise that the roof will look new for that period. Most […]
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