Most cabinets and enclosures are built from one of three sheet products: plain cold-rolled steel, galvanneal, or hot-dip galvanized. They look similar on a drawing and behave very differently in the shop and in the field. The choice affects corrosion life, powder coat adhesion, weld quality and cost. Here is how they compare and where each belongs.
Want a design-for-fabrication review on your drawing? Call 601.892.5017 or email collin.t@fabtekindustries.com — send the model or drawing and our engineers will mark it up.
- Cold-rolled (ASTM A1008): uncoated, smooth, lowest cost, easiest to weld and paint — right for indoor painted parts, where the coating alone protects it.
- Galvanneal (A653, e.g. A60): zinc coating alloyed with iron by heat treatment — matte, excellent for paint and powder, welds well; a common choice for painted outdoor enclosures.
- Galvanized (A653, e.g. G90): heavier pure-zinc coating (about 0.9 oz/ft² total), the most corrosion protection bare, but harder to paint and weld — best for unpainted or duplex service with proper pre-treatment.
- Sheet Metal Gauge Chart
- How to Tolerance a Sheet Metal Drawing
- K-Factor, Bend Allowance & Bend Deduction
- Weld Symbols & Weldment Design
- Designing for Hot-Dip Galvanizing
- Designing for Powder Coat
- PEM Hardware vs. Stud Welding vs. Tapped Holes
- Galvanneal vs. Galvanized vs. Cold-Rolled Steel (you are here)
Side-by-side comparison
| Cold-rolled | Galvanneal (A60) | Galvanized (G90) | |
|---|---|---|---|
| Specification | ASTM A1008 | ASTM A653 / A924 | ASTM A653 / A924 |
| Coating | None (oiled) | Zinc-iron alloy, 0.60 oz/ft² total both sides | Pure zinc, 0.90 oz/ft² total both sides |
| Approx. coating per side | — | ~0.5 mil | ~0.75 mil |
| Surface | Smooth, bright | Matte gray, no spangle | Bright, may show spangle |
| Bare corrosion resistance | Poor | Moderate | Best of the three |
| Paint / powder adhesion | Excellent with pre-treatment | Excellent | Good only with proper pre-treatment |
| Weldability | Excellent | Good | Fair; zinc fume and burn-back |
| Forming | Excellent | Good; coating can powder on tight bends | Excellent |
| Relative cost | Lowest | Middle | Middle to higher |
Coating weights are total for both sides per ASTM A653; per-side thickness is approximate (about 1.7 mils of zinc per oz/ft²).
Coating designations explained
ASTM A653 designates zinc coatings with a G (galvanized, pure zinc) or A (galvannealed, zinc-iron alloy) followed by the total coating weight in hundredths of an ounce per square foot, both sides combined. G90 is 0.90 oz/ft²; G60 is 0.60; A60 is 0.60 oz/ft² of alloyed coating; A40 is lighter. Galvanneal is made by passing freshly galvanized strip through a furnace so iron diffuses into the zinc, turning the coating into a hard, matte zinc-iron alloy. That coating is slightly less protective than the same weight of pure zinc, but it is a far better base for paint.
Paint and powder adhesion
Cold-rolled steel takes paint and powder very well after cleaning and a conversion coating; it simply has nothing underneath if the coating is breached. Galvanneal’s matte, slightly rough alloy surface gives paint and powder excellent adhesion with standard pre-treatment, which is why it is widely used for painted appliance, HVAC and electrical enclosures. Galvanized sheet is smooth pure zinc, often with a passivation treatment from the mill; paint adhesion can be poor unless the surface is properly cleaned and pre-treated for zinc, and zinc can outgas under powder in the oven. Done correctly, powder over galvanized — a duplex system — gives the longest life of all.
Welding and cut edges
Cold-rolled welds cleanly. Galvanneal welds well with MIG, laser and resistance welding, with modest zinc fume. Galvanized sheet releases more zinc fume, requires ventilation and good technique, and the coating burns back from the weld; welds and heat-affected areas are touched up with zinc-rich paint (ASTM A780) or covered by the powder system. Laser-cut edges of both coated products are bare steel with a little zinc drawn over them, which is why outdoor enclosures from coated sheet are still pre-treated and powder coated rather than left bare (see Fiber Laser Cutting).
Which to choose
Indoor cabinets, control panels, switchgear sections and internal parts — cold-rolled steel with a single powder coat. Outdoor NEMA 3R enclosures, pad-mount cabinets and BESS enclosures — galvanneal with a two-coat powder system is a common, cost-effective choice, and some specifications call for galvanized with duplex powder for maximum life. Unpainted parts — brackets, cable-tray supports, internal hardware in mild environments — G90 galvanized. Coastal and corrosive sites — consider galvanized plus powder, or stainless (NEMA 4X), and specify the coating system to IEEE C57.12.28/.29 where it applies. Many customers already have a standard; the right answer is the one the equipment spec and the site environment require.
How to write it
“Enclosure panels and doors: 0.1084″ (12 ga) galvannealed steel, ASTM A653 CS Type B, A60 coating; pre-treat and powder coat, two-coat system, 3–5 mils total. Internal mounting panels: 0.0747″ (14 ga) cold-rolled steel, ASTM A1008 CS Type B, powder coat white. Weld areas on coated steel shall be cleaned and covered by the finish system; field repairs per ASTM A780.”
How FabTek handles it
FabTek cuts, forms and welds cold-rolled, galvanneal and galvanized sheet on its fiber lasers, press brakes and laser welding cell, then pre-treats and finishes in house on the automated powder coat line to an IEEE 2,000-hour salt-spray certified system. Engineering confirms the sheet product, coating weight and finish system against the customer’s specification during DFM review, and heat numbers are carried from coil to part.
Frequently asked questions
What is the difference between galvanneal and galvanized steel?
Both are zinc-coated sheet to ASTM A653. Galvanized has a pure zinc coating; galvanneal is heat-treated after coating so the zinc alloys with iron, giving a matte surface that paints and powder coats very well and welds more easily, but with somewhat less bare corrosion resistance than the same weight of pure zinc.
What does A60 galvanneal mean?
A60 is a galvannealed coating designation under ASTM A653: a zinc-iron alloy coating weighing 0.60 ounces per square foot in total for both sides, roughly 0.5 mil per side. It is a common coating for painted enclosures and cabinets.
What does G90 mean on galvanized steel?
G90 is a pure-zinc galvanized coating of 0.90 ounces per square foot in total for both sides, roughly 0.75 mil per side, under ASTM A653. It is a common coating for unpainted parts and for duplex (galvanized plus paint) systems.
Can you powder coat galvanized steel?
Yes, with proper pre-treatment for zinc surfaces and attention to outgassing during cure. Powder over galvanized, called a duplex system, gives very long life. Galvanneal is easier to powder coat because its alloyed surface accepts paint readily.
