TL;DR
Iron rusts and aluminum does not -- that single difference drives everything. On iron, the coating is the only thing between the metal and rust, so any chip is a repair job. On aluminum, the surface oxidizes to a chalky gray that looks like damage but is actually the metal protecting itself. Both need washing, drying, and a look at the coating twice a year.
Wrought iron: the coating is everything
Wrought iron and steel furniture is protected by paint or powder coating. As long as that layer is continuous, the metal underneath is fine. Where it chips, cracks, or wears at a contact point, water gets to bare iron and rust starts.
Rust then spreads under the surrounding coating, lifting it in a widening ring. That is why a small chip left alone for a season becomes a palm-sized bubble.
So the maintenance job is really two jobs: wash the surface, and inspect the coating.
Washing iron furniture
Mix warm water with dish soap. Wash with a soft brush or a sponge, working into the scrollwork and the joints where debris collects. Rinse with a hose on a normal setting.
Then dry it. This is the step that matters most and the one people skip because it is outdoor furniture and it seems absurd to towel it off. But water sitting in a hollow leg, at a weld, or in a joint is exactly where rust starts, and a few minutes with a towel plus an hour in the sun prevents a season of corrosion.
Tip chairs and tables to drain hollow sections. Many outdoor frames have small drain holes -- check that they are clear, the same principle as the weep holes on a window.
Source: outdoor furniture manufacturer care guidance.
Dealing with rust spots
Catch them small. Scrub the rust off with a wire brush, sandpaper, or an abrasive pad until you reach clean metal, feathering the edges of the surrounding coating so the repair does not show as a ridge.
Wipe away dust, let the area dry completely, and apply a rust-inhibiting primer made for metal, then a matching exterior enamel or coating. Two thin coats beat one thick one.
Do this on a dry day with low humidity. Priming over damp metal traps moisture and the rust simply continues underneath.
For heavy, structural rust -- flaking sheets, holes, weakened joints -- cleaning is not the answer. That is a refinishing or replacement decision, and a piece with a compromised leg or a rusted-through weld is a safety issue.
Cast aluminum: chalking is not damage
Cast aluminum furniture is powder coated, and under the coating the metal itself does not rust. What happens instead is that where the coating wears thin or fails, the aluminum oxidizes to a dull chalky white or gray.
Run a finger over it and you get a powdery residue. That is aluminum oxide, and it is a self-limiting protective layer rather than an ongoing corrosion problem. Structurally the piece is fine.
Washing removes the loose chalk. Getting the original finish back requires recoating, which is a refinishing job. Some people apply a car wax or a product intended for painted metal to reduce the chalky appearance and add some protection, which helps cosmetically without being a permanent fix.
The same oxidation shows up on aluminum window screen frames, discussed in cleaning window screens.
Side by side
| Wrought iron and steel | Cast aluminum | |
|---|---|---|
| Magnetic | Yes | No |
| Weight | Heavy | Light |
| Corrosion type | Rust -- structural, spreads under coating | Oxidation -- chalky, cosmetic, self-limiting |
| Coating failure | Urgent; leads to real damage | Cosmetic; metal stays sound |
| Drying after washing | Essential | Good practice |
| Repair | Sand, prime, repaint the spot | Wash; recoat only for appearance |
| Winter storage | Strongly recommended in a wet climate | Helpful but less critical |
What not to use on either metal
| Avoid | Why |
|---|---|
| Chlorine bleach | Corrodes and pits both metals and degrades coatings |
| Mixing bleach with any acid or ammonia product | Toxic gas; there is no reason to use bleach here at all |
| Strong alkaline degreasers on aluminum | Etch and darken aluminum permanently |
| Abrasive powders on intact coating | Cut through the protection you are trying to preserve |
| Pressure washing at close range | Drives water into joints and blasts coating off edges |
| Leaving furniture wet through the wet season | The single biggest cause of rust on iron pieces |
Living with them in a wet climate
The Willamette Valley's long rainy season is hard on outdoor metal, and the practical strategy is not exotic.
Cover or store furniture between fall and spring. A breathable cover is better than a sealed tarp, which traps condensation against the metal and can be worse than leaving the piece uncovered.
Keep feet off wet concrete for months at a time. Concrete stays damp, wicks moisture into a hollow leg, and rusts iron from the bottom up. Plastic or rubber glides lift the foot slightly and make a real difference, though note that some rubber compounds mark stone patios.
Inspect twice a year -- spring and fall. Look at contact points, welds, undersides, and anywhere two parts meet. Touch up chips as you find them rather than waiting.
Mixed-material furniture
A lot of patio furniture combines metal frames with glass tops, sling fabric, or wood slats, and each material has its own routine. Chrome and plated hardware pits from abrasives and acids, covered in cleaning chrome without scratching. Brass fittings may be lacquered, in which case polish ruins them, explained in lacquered versus unlacquered brass. Copper accents develop deliberate patina, in cleaning copper and its patina. Stainless hardware is pitted by chloride, discussed in why bleach pits stainless steel.
When in doubt on a mixed piece, wash the whole thing with mild soap and water and dry it, then address individual materials separately.
FAQ
How do you remove rust from wrought iron furniture?
Scrub the rust back to clean metal with a wire brush or sandpaper, feathering the edges of the surrounding coating. Wipe away dust, let it dry fully, then apply a rust-inhibiting metal primer and a matching exterior enamel in two thin coats on a dry day.
Why is my aluminum patio furniture chalky?
The powder coating has worn thin and the aluminum underneath has oxidized. That white powder is aluminum oxide, which is protective rather than destructive -- the metal is structurally fine. Washing removes the loose chalk; restoring the finish requires recoating.
Can you pressure wash outdoor metal furniture?
Only at a distance and on a low setting, if at all. Close-range pressure blasts coating off edges and drives water into joints and hollow sections where it causes rust. A hose, mild soap, and a soft brush do the job with none of that risk.
Should you use bleach on outdoor furniture?
No. Chlorine bleach corrodes both iron and aluminum, degrades protective coatings, and must never be combined with acids or ammonia cleaners. Mild dish soap and water handle outdoor grime, and a soft brush handles what soap alone does not.
How do you tell wrought iron from cast aluminum?
Hold a magnet to it -- iron and steel are magnetic, aluminum is not. Weight is the other giveaway: an aluminum chair lifts with one hand easily, while an iron one is genuinely heavy and awkward to move.
The whole-house equivalent of this routine is covered by house cleaning services.
Both metals last decades with a wash, a dry, and a twice-yearly look at the coating. Every home is different, so what a full clean covers depends on size, condition, and what you want included. Get a quote and we will walk you through it.