Resources / Reference

Glossary

Aluminum coil terminology, defined plainly: the terms used across this site and in RFQ conversations.

Alloy series

The four-digit number identifying an aluminum alloy's primary alloying element: 1xxx is near-pure aluminum, 3xxx is manganese, 5xxx is magnesium, 6xxx is magnesium and silicon, 7xxx is zinc.

Coil ID / OD

Inner diameter and outer diameter of a wound coil: ID must match the customer's uncoiler mandrel, OD affects total coil weight and handling.

Coil set

The tendency of coil to retain a curved shape after being uncoiled, from having been wound tightly. Excess coil set causes feeding and flatness problems downstream.

Cut-to-length

A processing step where coil is sheared into individual flat sheets at a specified length, rather than left in continuous coil form.

Delta-E (ΔE)

A numeric measure of the visual difference between two colors. Lower delta-E means a closer color match, used to confirm coating color consistency batch to batch.

Dry film thickness (DFT)

The thickness of a coating after it has cured, measured to confirm it meets the specified thickness for performance and warranty purposes.

Galvanic corrosion

Accelerated corrosion that occurs when two dissimilar metals (such as aluminum and steel) are in direct contact in the presence of an electrolyte like moisture or salt air, without isolation between them.

MEK rub

A solvent resistance test where a cloth soaked in methyl ethyl ketone is rubbed against a coating a set number of times to confirm the coating has fully cured.

Mill finish

The natural, uncoated surface of aluminum as it comes off the mill, not polished or treated beyond standard production.

Oil canning

Visible waviness or rippling in a flat metal panel, caused by internal stress or coil flatness variation. It's a cosmetic issue, not a structural failure, but it's the most common complaint on flat metal roofing and cladding.

Pencil hardness

A coating hardness test using graded pencil leads of increasing hardness, pressed against the coating until it scratches; the hardest pencil that doesn't mark the coating is the result.

RAL

A European color-matching standard widely used to specify coating colors precisely, identified by a four-digit code (for example RAL 9006, a standard silver).

Slitting

A processing step where a wide coil is cut lengthwise into narrower coils at specified widths, using rotary blades.

Stucco embossing

A repeating texture pattern rolled into coil during production, which adds stiffness, hides handling marks, and reduces glare compared to a flat surface.

T-bend

A coating flexibility test: the coated sheet is bent back on itself around a mandrel of a specified thickness, and the coating is checked for cracking at the bend.

Temper

The heat treatment and/or work-hardening state of an alloy, denoted by a letter and number suffix: for example T6 (solution heat-treated and artificially aged) or H14 (strain-hardened, half-hard). Temper changes strength and formability without changing the alloy itself.