Outdoor furniture listings treat “anodized” and “powder-coated” as if they were two rungs on the same ladder. They are not. They are different kinds of protection, they fail in different ways, and — this is the part nobody selling furniture wants to say — the specification class matters more than which of the two words is on the page.
The one difference that explains everything else
Powder coating and paint are films. They are applied on top of the metal and held there by a chemical pretreatment layer.
Anodizing is not applied at all. It is an electrochemical process that converts the surface of the aluminum itself into an oxide layer. The Aluminum Anodizers Council describes the result as “fully integrated with the underlying aluminum substrate, so it cannot chip or peel” (anodizing.org). The Aluminum Extruders Council puts it the same way: the parts go into an acid electrolyte bath, current is passed through, and “the resulting oxide layer will not chip or peel” (aec.org). Color on an anodized part is dyed into the pores of that oxide layer, not sprayed onto it.
That single structural difference drives the whole comparison:
- A film can be breached. Scratch a powder-coated frame down to bare metal and moisture gets underneath the coating.
- An integral layer cannot chip off — but it is only as protective as it is thick, and decorative anodizing is very thin.
The numbers that are worth asking for
Anodizing: ask for the class, in mils
AAMA 611 defines two architectural classes. Class I is a minimum of 0.7 mil (18 microns); Class II is a minimum of 0.4 mil (10 microns), and Class II is an interior specification. Class I is required to withstand 3,000 hours of accelerated salt spray, Class II only 1,000 (Linetec).
The Aluminum Anodizers Council's own specification bulletin sets the bands: under 0.4 mil is “protective and decorative”; 0.4–0.7 mil is Architectural Class II; 0.7 mil and above is Architectural Class I. Marine products are specified at 0.7 to 1.2 mil (AAC Technical Bulletin).
So “anodized” on its own spans everything from a cosmetic flash of a few ten-thousandths of an inch to a genuine marine finish. They are not the same product, and only one of them is a corrosion story.
Powder and paint: ask for the AAMA number
Painted and powder-coated architectural aluminum is graded by three specifications, and the gap between them is large (Linetec):
| Spec | Salt spray | South Florida weathering | Minimum film | Typical use |
|---|---|---|---|---|
| AAMA 2603 | 1,500 hrs | 1 year, slight fade allowed | 0.8 mil | interior, low expectation |
| AAMA 2604 | 3,000 hrs | 5 years | 1.2 mil | storefronts, high traffic |
| AAMA 2605 | 4,000 hrs | 10 years | 1.2 mil | monumental, 70% PVDF |
The 2604 requirements are independently confirmed in the testing protocol published by AMICO: 3,000 hours to ASTM B117 in a 5% salt solution, 3,000 hours humidity at 100°F and 100% relative humidity, and five years of Florida exposure at 45° facing south (AMICO).
A warning about salt-spray hours, including ours
You will see “3,000 hours salt spray” used in marketing as if it converted into years at the beach. It does not, and the standard itself says so. ASTM B117 states that “prediction of performance in natural environments has seldom been correlated with salt spray results when used as stand alone data,” and that correlation “should be considered only in cases where appropriate corroborating long-term atmospheric exposures have been conducted” (ASTM B117-19).
Salt-spray hours are a comparative laboratory number, useful for ranking finishes tested the same way. They are not a lifespan. And the 3,000 hours in AAMA 611 Class I and the 3,000 hours in AAMA 2604 come from different specifications with different protocols — putting them side by side and declaring a winner would be dishonest, so we are not going to.
How each one actually fails
Powder coating: filiform corrosion
The characteristic coastal failure of powder-coated aluminum has a name. QUALICOAT UK & Ireland describes filiform corrosion as “a spider like corrosion that creeps under the powder coating and runs along the aluminium grain boundaries” (QUALICOAT UKI). It begins wherever the film is breached or thin — a chip, a sharp edge, a scratch from a concrete step.
The recognized defense is not a thicker color coat. It is a deeper etch before coating: the QUALICOAT Seaside class doubles the minimum aluminum removal from 1 g/m² to 2 g/m² and requires applicators to pass an additional filiform corrosion test. For pool environments specifically, Products Finishing recommends a conversion coating, a powder primer, and a second layer for edge coverage, and warns against designs with exposed metal or crevices that trap moisture (Products Finishing).
In other words: with powder coating, the pretreatment you cannot see does more work than the color you can.
Anodizing: thinness, and chlorine
An anodized layer cannot peel, but a thin one can be worn through, and it is not a universal answer either. On the finishing industry's own technical forum, the consistent view is that “chlorine in a swimming pool is always a problem” for anodized aluminum, and that a bright decorative anodize is only a few ten-thousandths of an inch thick (finishing.com). A cosmetic anodize is not a pool-duty finish.
Maintenance matters for both. Mineral deposits and construction residue should be rinsed off promptly, and that is “especially true for mill-finish or anodized surfaces” (Products Finishing).
What to actually ask a seller
- Which process, and to what class? “Anodized” should come with a thickness in mils or microns. “Powder-coated” should come with an AAMA number, or at minimum a description of the pretreatment.
- What pretreatment? For a coated frame this is the question that predicts coastal life. A seller who has specified a Seaside-class or high-etch pretreatment will know it; one who has not will change the subject.
- Are the fasteners and hardware the same metal? Corrosion usually starts at the joints, not in the middle of a tube.
- What happens at the edges? Sharp edges hold less film. Ask whether edges are radiused, and whether there is a primer coat.
- Is there a written warranty against finish failure, and does it survive coastal or pool use? Many exclude exactly the environment you are asking about.
The honest conclusion
Neither finish is universally better. A Class I or marine-thickness anodize is an excellent, unpeelable finish. A properly pretreated AAMA 2604 or 2605 powder coat is an excellent, tough finish in a wider range of colors. A thin decorative anodize and a single-coat powder over a minimal pretreatment are both mediocre, and both get sold using the same two words as the good versions.
Ask for the class. If the answer is a marketing adjective, you have learned something anyway.
We hold ourselves to this too. Our own frames are described on the product pages for the Bosphorus folding sun lounger and the ChillGo folding lounge chair; where we have not yet published a figure to the standard above, we would rather you ask us than assume.