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Aluminium vs steel windows: rust, weight, sightlines and cost

Steel and aluminium both make good windows when they are specified and protected properly. This guide compares them on neutral criteria, explains what galvanising does, and says plainly where cost data is missing.
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THE SHORT ANSWER

Steel wins on slim frames, aluminium on weight and simpler upkeep

In the aluminium vs steel windows choice, steel is stronger and gives the slimmest frames, but it rusts once its zinc and paint layers are breached. Aluminium is about a third of the weight, does not rust and suits most homes and sea-air sites with the right coating. Which costs less depends on which steel window you mean.
Three different products are sold as steel windows in India. Fabricated galvanised iron or mild steel windows are listed on directories at roughly Rs 435 to 980 per sq ft. Slim, Crittall-style steel windows are described by guides as premium and often imported, with no published rupee figure. Steel-look aluminium copies the slim black frame in aluminium. We work with AluK Home aluminium systems and do not make steel windows; if you choose steel, ask the fabricator for proof of hot-dip galvanising and the coating specification.

Aluminium and steel windows compared

Steel here means galvanised and coated steel, the protected form. Bare steel is not a fair comparison.
CriterionAluminiumSteel, galvanised and coated
Rust and corrosionDoes not rust; a thin oxide film protects it, but salt attacks bare aluminiumBare steel rusts; zinc and powder coat protect it while intact
WeightDensity about 2.70 g/cm³, roughly a third of steelHeavy; needs sturdy fixing and lintel
SightlinesSlim systems exist, such as a 21 mm sliding interlock; standard sections are widerSlimmest; a steel mullion can be a third of the width, guides say
HeatConducts heat; thermally broken systems are commonConducts heat; slim sections rarely take a thermal break
MaintenanceLow: cleaning, clear weep holes, touch up chipsLow to medium: touch up coating, lubricate hinges
Sea airMarine-grade powder coat or anodising, SS 316 hardwareRisky unless the coating is perfect, guides say
Cost directionMainstream; standard windows Rs 300 to 950 per sq ft in guidesGI or MS listings Rs 435 to 980; slim steel described as premium
Typical useMost homes, large sliding and folding doorsHeritage or industrial look with the thinnest frames

Sources: Studiomatrx steel, coastal and durability guides (June 2026), Wikipedia on aluminium and galvanisation, AluK Home sliding doors page, IndiaMART steel window listings (Oct 2026), Houseyog (May 2026). Vendor figures, not test results.

What galvanising does, and where it stops

Steel rusts when bare. The usual protection is hot-dip galvanising, a zinc coating, followed by powder coat. Painting over bare steel is not galvanising, a point one guide makes plainly. Zinc protects steel sacrificially, because zinc is more reactive than iron, and reference sources say it keeps protecting exposed steel within about 5 mm of a scratch or cut.
Coating thickness sets coating life. The Galvanizers Association of Australia, an industry body for galvanising, says coating life is proportional to thickness, that chlorides near the sea speed corrosion and that surf coasts can sharply cut coating life, while calm coasts are relatively benign beyond 50 m of high tide. Its figures are for Australian sites, so we do not convert them into an Indian service life.
Aluminium does not rust, because it contains no iron. It forms a thin oxide film, about 5 nanometres, that protects it from further corrosion. Chlorides and salt water greatly reduce that resistance, especially where aluminium touches a different metal, so bare aluminium pits in coastal air. The coating and the hardware matter on both materials.

WEIGHT AND SIGHTLINES

Weight, strength and how slim the frame can be

Steel is much stronger, so its sections can be thinner. One Indian guide says a steel mullion can be a third of the width of an equivalent aluminium one, and describes classic Crittall-style profiles at roughly 20 mm. The price of that strength is weight: steel frames are heavy and need sturdy fixings and a sound lintel.
Aluminium has a density of about 2.70 g/cm³, roughly a third of steel’s. Lighter frames put less load on fixings and lintels, which helps with large sliding and folding panels. Slim aluminium systems exist too: AluK Home’s Infineo sliding door has a 21 mm interlock. We do not claim it matches the thinnest steel; the right comparison is the frame you want against the panel size you need. Our aluminium vs uPVC guide covers the other common material choice.

Both metals carry heat through the frame

Both metals conduct heat. Published conductivity values used in window modelling put aluminium at about 160 W/(m.K) and steel at about 50, but a frame’s performance depends on its section design, thermal break and glass, not on the metal alone. Slim steel sections rarely take a polyamide thermal break, one guide notes, so the frame stays a heat path and it suggests low-E double glazing with outside shading instead. Many aluminium systems carry a thermal break; our thermal break guide explains what it does.
If road noise rather than heat is the reason for replacing, glass and seals do most of the work in either metal; our soundproof windows price guide sets out what each acoustic upgrade adds.

Coastal sites: why the coating matters most

Near the sea, both materials depend on their coating. A coastal guide says galvanised steel lasts a long time only with hot-dip galvanising and powder coat fully intact, and that un-galvanised steel rusts, jams sashes and stains the wall below. It calls steel on the coast risky unless the coating is perfect, and recommends marine-grade aluminium or uPVC as safer defaults.
For aluminium, the same guide asks for marine-grade powder coat or anodising in writing and SS 316 hardware, because bare aluminium pits in salt air. Cut edges and chips are where coating trouble starts on either metal. Our coastal homes page covers specification for sea-facing sites, and stainless grade matters for balcony railings too, as our glass railing price guide notes.

COST

Steel and aluminium listing prices side by side

At listing level the two overlap. Directory listings for galvanised or mild steel windows sit at roughly Rs 435 to 980 per sq ft (IndiaMART, October 2026), while published guides list standard powder-coated aluminium at Rs 300 to 950 (Houseyog, May 2026; Studiomatrx, June 2026). On a 4 ft by 5 ft window, 20 sq ft, that is Rs 8,700 to 19,600 for the steel listings and Rs 6,000 to 19,000 for the aluminium guides. Arithmetic on asking prices, not quotes.
At the premium end, guides describe genuine slim steel as broadly in line with or above premium aluminium systems, and a UK seller says aluminium is cheaper as a raw material and to fabricate. Nobody publishes a verified Indian figure for Crittall-style steel. Compare like for like: same size, same glass, same finish, both installed. Our aluminium window price guide lists published rates by type.

No independent 20 year cost data exists, so build your own

We looked for an independent 20 year cost comparison and found none. Guide sites claim 60 to 100 years for galvanised, coated steel and 30 to 50 years for marine-grade aluminium, and a UK vendor site gives 60 years or more for steel and 30 to 40 for aluminium, excluding paint. None of these cites a test. Steel sellers argue a longer life cuts replacement cost; aluminium sellers argue lower upkeep. Rather than invent a total, fill in this worksheet with your own written quotes.
  • Supply and installation price for the same openings, glass and finish
  • Recoating or touch-up interval and cost, from the supplier in writing
  • Hardware replacement: hinges, rollers, locks, and their expected interval
  • Yearly cleaning and inspection time, more often on the coast
  • Warranty documents for the profile, the coating and the hardware, separately

When steel fits, and when aluminium does

Choose aluminium for most homes

Standard residential windows, large sliding and folding doors, upper floors where weight matters and sea-air sites with a marine-grade coating. Aluminium is lighter, carries thermally broken systems and needs less routine care, guides say. Our window maintenance guide covers the routine.

Choose steel for the thinnest frame

A heritage or industrial look where the slimmest frame matters more than weight, on a site that is inland or well maintained. Budget for hot-dip galvanising and a good coating, and for strong fixings. Ask the fabricator for galvanising and coating proof before you order.

Consider steel-look aluminium

If you want the black grid look on a coastal or upper-floor home, steel-look aluminium copies the style with a slightly fatter frame, one guide says. Check the sightline on a sample at the showroom rather than in a photo.

Avoid uncoated or painted-only steel

Bare or simply painted steel will rust, especially near the sea, and rust stains walls and jams sashes. If a low steel price shows no galvanising on paper, assume there is none, and ask before you compare it with a coated aluminium price.

FAQ

Aluminium vs steel window questions

Answers to the questions people ask when choosing between the two metals.
It depends on the steel. Directory listings for simple galvanised or mild steel windows, about Rs 435 to 980 per sq ft (IndiaMART, October 2026), overlap standard aluminium at Rs 300 to 950 in published guides. Guides describe slim Crittall-style steel as premium, with no published Indian price. No independent comparison exists, so compare written quotes for the same size and glass.
Bare steel does. Hot-dip galvanising followed by powder coat protects steel while the coating is intact, and zinc keeps protecting small scratches nearby. Chips and cut edges are the weak points, and salt air near the coast speeds corrosion. Ask for galvanising proof in writing; painting over bare steel is not the same thing.
No. Aluminium contains no iron, so it cannot rust, and it forms a thin oxide film that protects it. Salt and chlorides can still corrode bare aluminium, especially next to a different metal, which is why coastal homes need a marine-grade powder coat or anodising and stainless steel hardware.
Steel is much stronger, which is why its frames can be so slim; one guide says a steel mullion can be a third of the width of an aluminium one. Aluminium is about a third of the weight, which suits large sliding panels and upper floors where heavy frames need heavy fixings.
Guide sites claim 60 to 100 years for galvanised, coated steel and 30 to 50 years for marine-grade aluminium, but none of these figures cites independent testing. Either material lasts only as long as its coating and hardware are maintained. Ask each supplier what the warranty covers and what upkeep it requires, in writing.
Guides call steel on the coast risky unless the galvanising and coating are perfect, and recommend marine-grade aluminium or uPVC as safer defaults. If you choose steel near the sea, budget for hot-dip galvanising, a good powder coat and prompt touch-up of chips, and check the coating every year.
No. We supply and install AluK Home aluminium windows and doors, including slim sliding systems, from our showroom in Belagavi. For genuine steel windows, ask a steel fabricator for galvanising and coating proof. If you are comparing the two, send us your sizes and we will price the aluminium option after measurement.

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Visit the AluK Home Experience Center in Tilakwadi, Belagavi, or send your opening sizes for a measured quote.
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