Galvanized Steel Carports: Coating, Where Rust Starts and Cost
CarportBay Editorial Team Reviewed
Last verified:
Galvanized steel carports have a zinc coating, but a listing rarely says how much zinc or how it was applied. Of 14 carport seller sites read, 11 print galvanized or a zinc coating for the frame and none prints a coating weight. Ask each seller for the process, grade and rust-through terms in writing before you compare prices.
| Question | Answer in the sources |
|---|---|
| Sites printing galvanized frames? | 11 of 14 read |
| Sites printing a zinc weight? | 0 of 14 read |
| G90 zinc per side? | About 19 micrometers |
| Hot-dip tube minimum (A123)? | 45 micrometers average |
On this page
What does galvanized mean on a carport?
On a carport, galvanized means zinc-coated steel, and it can describe coated sheet, tube galvanized in a mill line, or a frame dipped in zinc after it is built.
Steel carport frames, gauges and prices sit on the steel carport page, and this page covers the zinc coating.
Sheet or tube made from zinc-coated coil carries zinc on both faces, labelled G60 or G90. Tube galvanized in a mill line carries zinc outside and a zinc-based coating inside. A frame dipped in zinc after it is built carries a thicker zinc-iron layer on every surface, welds and cut ends included. That grouping is CarportBay's summary of trade and maker pages.
| Coating | Source | Zinc weight, oz per sq ft | Micrometers per side | Mils | Times G90 |
|---|---|---|---|---|---|
| G60 coil sheet or tube | ASTM A653 | 0.60, both sides | 12.8 (calc) | 0.50 | 0.67 |
| G90 coil sheet or tube | ASTM A653 | 0.90, both sides | 19.2 (calc); AGA 18, GalvInfo 21 | 0.76 | 1.00 |
| In-line tube, AGA figure | ASTM A1057 | About 0.5, outside face | 21.4 (calc, one face) | 0.84 | 1.11 |
| In-line tube, Allied | Maker page | 1.0, outside face | 42.7 (calc, one face) | 1.68 | 2.22 |
| Hot-dip, tube walls under 1/8 in | A123 grade 45 | 1.0 per surface | 45 minimum average | 1.8 | 2.34 |
| Hot-dip, walls 1/16 to under 1/8 in | A123 grade 65 | 1.5 per surface | 65 minimum average | 2.6 | 3.38 |
| Hot-dip, walls 1/8 to under 1/4 in | A123 grade 75 | 1.7 per surface | 75 minimum average | 3.0 | 3.90 |
These are the published figures of the sources named, read on the dates shown, and the printed standard governs. They describe zinc layers in general, not any carport here, and the page does not say that any product meets any standard.
The American Galvanizers Association (AGA) is a trade body for hot-dip galvanizers, so the hot-dip rows come from an interested source. G90 is about 19.2 micrometers a side by calculation, and grade 45 is 2.34 times that. A dipped 14 or 12 gauge wall falls in the grade 45 row. No row says which layer a carport seller uses.
Sellers write metal carport for any metal. Read metal carports across materials and styles and how an aluminum carport differs from steel.
Type a coating weight or thickness from a seller's answer to see the zinc layer in micrometers and mils.
What do carport sellers print about galvanized?
Of 14 carport seller sites read on 2026-10-06, 11 print galvanized or a zinc coating for the frame and none prints a coating weight, grade or standard.
Eagle Carports, Legacy Carports and Absolute Steel print neither word. No seller names a G-number, a zinc weight or an ASTM number, and no product page read names a process.
This table reports what each seller prints on the pages read.
| Seller | Frame wording as printed | Process, weight, grade or standard | Frame rust-through term |
|---|---|---|---|
| AA Metal Buildings | "Galvanized steel frame" | None | 20 years |
| Absolute Steel (TX) | Not stated | None | Not stated |
| Alan's Factory Outlet | "galvanized steel square tubing"; sheet "baked enamel" | None | 20 years on 12 gauge only |
| American Metal Buildings | "galvanized steel components" | None | "up to 20-year" |
| American Steel Carports | "14 gauge galvanized"; blog claims hot-dip frames | Blog says hot-dip, no weight | 10 years on 14 gauge; 20 on 12 |
| Carport Central | Galvanized frame; blog says hot-dip for sheets | Blog says hot-dip, no weight | 20 years, 12 and 14 gauge |
| Carport Direct | "Galvanized steel construction" | None | 20 years, 12 and 14 gauge |
| Carport.com | "galvanized frames" | None | 20 years on 12 gauge; 14 gauge 30-day workmanship |
| Coast to Coast Carports | Frames "galvanized" | None | 20 years on 12 gauge only |
| Eagle Carports | Not stated | None | Not stated |
| Keen's Buildings | Frame of "galvanized tubing" | None | "20-year warranty" |
| Legacy Carports | Not stated | None | "20 year warranty", not a rust-through term |
| Midwest Steel Carports | "a protective zinc coating" | None | 7 years on 14 gauge; 20 on 12 |
| Viking Steel Structures | "100% Galvanized Steel" | None | 20 years, limited |
Four sellers print 2 1/2 in tube at 14 gauge and 2 1/4 in at 12 gauge, and a tube size says nothing about zinc. Steel carport parts and tube sizes get their own page.
Three sellers call their roof sheet painted or enameled, and none names the coating under the paint.
Retail kits at Home Depot and Tractor Supply print galvanized for the roof, the frame or both, and one listing says galvanized frame in its title and powder coated frame in its body.
Rust-through terms run from 7 to 20 years. Five sellers attach 20 years to 12 gauge only, and the 14 gauge term is 7 years at Midwest and 10 at American Steel Carports, which excludes "water under the base rail." No warranty page read mentions scratches, cut ends, coast or salt.
A warranty length is the seller's term, not a lifespan or a standard.
Ask each seller four things in writing: the zinc process, the coating weight or standard, whether cut ends and welds are touched up, and the 14 gauge rust-through term.
Where does rust start on a galvanized carport?
Sources place rust on a galvanized carport frame at bare steel spots such as cut ends, drilled holes, welds and scratches, and where the zinc has worn away.
- Marker 1: Cut ends of tube. The AGA and Gibraltar describe bare cut edges.
- Marker 2: Drilled and bolt holes. Metals Depot, a tube seller, says holes need cold galvanizing compound.
- Marker 3: Welds. Metals Depot says welds need it too.
- Marker 4: Scratches. The AGA gives distances over which zinc protects a scratch.
- Marker 5: Base rail or post base on wet ground. American Steel Carports' warranty names water under the base rail.
- Marker 6: Inside the tube. Wheatland, a tube maker, describes a coating inside its in-line tube.
No carport seller page read mentions markers 1, 2, 3, 4 or 6, and the map does not rank the spots.
The AGA says zinc protects bare steel only a short distance: at most slightly over 1/4 in, and down to just over 1/8 in when the bare patch is wider. Scratches under 1/8 in need not be repaired in mild climates, and its trade pages say coastal, marine or chemical exposure means repairing even small ones.
GalvInfo Note 3.6, from the International Zinc Association, a zinc producers' body, reports a 1 mm sheet free of red rust at 6 months and a 2.3 mm sheet rusted within 2 weeks. A 14 gauge wall is about 1.9 mm, nearer the thicker sample. That reading is CarportBay's.
Gibraltar, a roof panel maker, says the edges of its metal are bare steel and field cuts hold up less well than factory cuts. Metals Depot, a tube seller, says saw cuts, drilled holes and welds need cold galvanizing compound. The base rail exclusion is the one seller term that names a wet place.
McElroy Metal, a roof maker, lists copper contact, including from pressure-treated lumber, uncured concrete and ponding water as corrosive to galvanized sheet. No source on carport base rails and concrete was found.
ASTM A153 covers zinc on hot-dip hardware such as bolts (ASTM), and no seller prints a standard for bolts or base plates. No source read defines red rust, so this page sets no threshold for it.
How long does galvanizing last?
No source read gives one service life for a galvanized carport, because zinc is lost at 0.1 to 8.4 micrometers a year by corrosion class.
A G90 layer is about 19 micrometers a side by calculation, and the setting sets how fast it is used up. The AGA says most North American sites, coastal included, are class C3, and the Hot Dip Galvanizers Association of South Africa ties C4 and C5 to sites within 1 km of the ocean.
| Class | Zinc loss (micrometers a year) | Setting as sources describe it | Crude zinc layer years, G90 (calc) |
|---|---|---|---|
| C2 | 0.1 to 0.7 | Rural, low pollution (AGA) | 26 to 210 |
| C3 | 0.7 to 2.1 | AGA: most North American sites, coastal included | 8.6 to 30 |
| C4 | 2.1 to 4.2 | HDGASA: within 1 km of the ocean | 4.3 to 10 |
| C5 | 4.2 to 8.4 | Same HDGASA line as C4 | 2.1 to 5 |
The years here are arithmetic, the zinc layer divided by a corrosion rate. They are not a prediction or a service life.
Portland Bolt, a fastener seller, quotes the AGA chart for a 2.5 mil hot-dip coating: rural 80 or more years, suburban 60, temperate marine 55, tropical marine 50 and industrial 45. That coating is thicker than G60 or G90 and CarportBay did not read the chart, so the values are second-hand and are not applied to G60 or G90.
A City of Nowthen, Minnesota, planner's memo gives about 15 to 20 years for a galvanized roof and cites no test. An Ontario farm factsheet says G90 truss plates show "severe corrosion within 5 to 10 years" in livestock barns. Neither is about a carport.
Two seller blogs claim longer lives, American Steel Carports for hot-dip frames and Metal America for G90 in mild climates, and neither cites a test.
Galvanized or Galvalume?
Galvanized sheet is coated in zinc and Galvalume in a 55 percent aluminum, 43.5 percent zinc alloy, and the makers read claim Galvalume resists corrosion longer.
| Point | Galvanized | Galvalume | Who says |
|---|---|---|---|
| Coating | Zinc, ASTM A653 | 55 percent aluminum, 43.5 percent zinc, ASTM A792 | GalvInfo Note 1.2 |
| Weight labels | G60 is 0.60 oz, G90 0.90 oz per sq ft, both sides | AZ50 is 0.50 oz per sq ft, not the same as G50 | Steelscape, McElroy |
| Corrosion claim | Zinc protects by sacrificing itself | Makers claim at least twice the corrosion resistance | Dofasco, Steelscape (makers) |
| Warranty as printed | None for galvanized sheet | Unpainted AZ50 40 years, excluding cut edges and within 1,500 ft of salt water | Steelscape, Dofasco |
| Conditions warned about | Copper contact, uncured concrete, ponding | Animal confinement, wet cement, buried soil, copper | McElroy, Dofasco, Steelscape |
| What carport sellers print | Frame: galvanized at 11 of 14; sheet usually painted | No seller names its sheet coating | Seller pages |
Every claim of longer corrosion resistance in the table is a maker's, and no source read compares the two on a carport.
The roof sheet is a separate product from the frame. Metal roof carport panels and coatings are on the metal roof carport page.
How much do galvanized carports cost?
Seller listings read on 2026-10-06 run from $4.49 to $9.67 per square foot of footprint, and no listing prices a carport by its coating.
These are the sellers' and retailers' own listed prices.
| Seller and listing | Price | What the price covers | $ per sq ft (derived) |
|---|---|---|---|
| Alan's, 20x20 boxed eave | $1,795 | Starting price; install not stated | $4.49 |
| Alan's, 24x25 vertical roof | $3,095 | Starting price; install not stated | $5.16 |
| Keen's, 22x25 | $2,870 | Sale price | $5.22 |
| Keen's, 30x30 | $4,783 | Sale price | $5.31 |
| Alan's, 12x20 regular roof | $1,295 | Starting price; install not stated | $5.40 |
| Carport Direct, 24x26 vertical | $4,050 | Starting at; select areas | $6.49 |
| Coast to Coast, 12x21 regular | $1,695 | Free delivery, install | $6.73 |
| Keen's, 12x20 | $1,620 | Sale price; free install | $6.75 |
| Coast to Coast, 20x20 regular | $3,305 | Free delivery, install | $8.26 |
| AA Metal Buildings, 20x20x7 | $3,866 | Starting at; free install | $9.67 |
The tables above report what each source states, so you can compare on their own words before you ask anyone for a price.
Rows differ in seller, size, roof style and what the price includes, so no premium is read from them. The AA Metal Buildings page is titled 20x21 and lists 20x20x7, so 20 by 20 is the footprint.
| Retailer and kit | Price | What the listing says about zinc | $ per sq ft (derived) |
|---|---|---|---|
| Home Depot, WD28-160 21x12 | $1,021.40 | All-metal galvanized steel | $4.05 |
| Home Depot, 12x20 marketplace | $1,084.62 | Title: galvanized frame; body: powder coated | $4.52 |
| Home Depot, Sudzendf 10x15x8 | $809.94 | Galvanized roof; powder coated frame | $5.40 |
| Tractor Supply, Arrow 12x24 | $1,599.99 | No coating stated | $5.56 |
| Tractor Supply, Arrow 20x24x7 | $2,842.99 | 29 gauge galvanized roof; powder coated frame | $5.92 |
| Home Depot, Arrow 12x20x7 | $1,658 | Galvanized steel | $6.91 |
| Home Depot, VAMOP 12x20x8.6 | $1,944.43 | Galvanized steel, no gauge | $8.10 |
Retail kits are a different price basis, because the buyer installs them. Kit prices exclude installation and run from $4.05 to $8.10 per square foot. See what a carport kit includes, before you read kit prices against the seller rows.
Prices change, so confirm the current price and what it includes. The two tables are not compared line to line, and no price here depends on the coating.
How do you care for a galvanized carport?
Sources read describe three care steps for galvanized steel: rinse off salt and dirt, check for scratches and bare edges, and repair damage with a zinc-rich product.
American Steel Carports, a seller, says rust is all about water and advises rinsing. Gibraltar says to wash Galvalume panels near the coast with fresh water at least twice a year. The AGA's check is to look for scratches and bare edges.
For repairs, the AGA, summarizing ASTM A780, lists three methods for hot-dip galvanized steel. Zinc-rich paint has 65 to 69 percent zinc in the dry film and goes on 50 percent thicker than the coating around it. Zinc solder and sprayed zinc are the other two. Clean off rust and oil first.
These repair figures are the AGA's summary of ASTM A780. Follow the maker's directions on any repair product. No source read says whether the A780 steps apply to pre-galvanized tube, so ask your seller.
The AGA, a galvanizing trade body, names ACQ and copper azole treated wood as active corrosion materials for steel and says hot-dip galvanized steel suits them. Wood carports and the steel hardware they use cover a wood frame.
Common questions
Seven questions cover the meaning of galvanized, rust, G90, hot-dip, service life, coastal use and touch-up.
Galvanized steel is steel coated in zinc to slow rust. On a carport listing, the word can mean zinc-coated sheet, tube galvanized at the mill, or a frame dipped in zinc after it is built. Of 14 seller sites read, none prints a coating weight.
Yes. Galvanized steel can rust where the zinc is cut through, worn away or used up, as at cut ends, drilled holes, welds and scratches. Zinc slows rust and does not stop it. Seller rust-through warranties run from 7 to 20 years, and a warranty is not a lifespan.
G90 is a zinc coating weight for galvanized sheet under ASTM A653: 0.90 ounce of zinc per square foot, both sides combined. That is about 19 micrometers a side by calculation. No carport seller read prints G90 for its own tube or sheet.
The listings read do not say. Hot-dip can mean tube dipped in zinc after it is built or tube galvanized in a mill line, and the zinc layers differ. Two seller blogs name hot-dip, one for sheets and one as a claim for frames. No product page read names a process.
No source read gives one life for a galvanized carport, because zinc loss depends on the setting and on how thick the layer is. Zinc is lost at 0.1 to 8.4 micrometers a year by corrosion class, and a G90 layer is about 19 micrometers a side. A seller warranty is not a lifespan.
Sources treat coastal air as harder on zinc, not as off limits. The American Galvanizers Association says even small scratches should be repaired in coastal exposure. No standards body distance was found, and warranty and seller distances run from 1,500 feet to 5 miles.
Under ASTM A780, written for hot-dip products, the American Galvanizers Association lists three repairs: zinc-rich paint, zinc solder and sprayed zinc. Clean off rust and oil first. Zinc-rich paint is 65 to 69 percent zinc in the dry film and goes on 50 percent thicker than the coating around it.
Ready to move forward
Get Matched With Installers Near You
Tell us a bit about your project and we will connect you with vetted installers and manufacturers who serve your area. There is no cost or obligation to request information.
See the affiliate disclosure page for how referrals work.
Where to read next
CarportBay's steel carport, metal carport, aluminum carport and carport kit pages continue from this galvanized steel carports page.
Sources
Each figure above is quoted from the page named, on the read date. Seller and retailer pages are cited by name and date. Standards are cited by number and edition, and no standard text is reproduced.
- AA Metal Buildings, 20x21 two car carport page (read 2026-10-06)
- Absolute Steel (TX), home page and price page (read 2026-10-06)
- Alan's Factory Outlet, home, carports and Florida pages and help center article on materials (read 2026-10-06)
- American Metal Buildings, metal carports page (read 2026-10-06)
- American Steel Carports, warranty page and blog posts (read 2026-10-06)
- Carport Central, home, warranty, blog and 18x20 carport pages (read 2026-10-06)
- Carport Direct, 24x26 vertical carport and warranty pages (read 2026-10-06)
- Carport.com, home page and building styles pages (read 2026-10-06)
- Coast to Coast Carports, metal carports, regular style carports and 12x21 pages (read 2026-10-06)
- Eagle Carports, home and metal carports pages (read 2026-10-06)
- Keen's Buildings, carports page (read 2026-10-06)
- Legacy Carports, home page (read 2026-10-06)
- Midwest Steel Carports, steel frame gauge options page (read 2026-10-06)
- Viking Steel Structures, Montana metal carports page (read 2026-10-06)
- Metal America, blog post on galvanized carports (dated 2026-03-21; read 2026-10-06)
- Home Depot, kit listings (read 2026-10-06)
- Tractor Supply, Arrow carport listing and metal carports category page (read 2026-10-06)
- American Galvanizers Association, ASTM A123/A123M grade table (read 2026-10-06)
- ASTM International, A123/A123M-17 store page (read 2026-10-06)
- ASTM International, A153/A153M store page (read 2026-10-06)
- ASTM International, A653/A653M-20 store page (read 2026-10-06)
- ASTM International, A780/A780M-20 store page (read 2026-10-06)
- ASTM International, A1057/A1057M-25 store page (read 2026-10-06)
- International Zinc Association, GalvInfo, Note 1.2, zinc and zinc-alloy coated sheet (read 2026-10-06)
- International Zinc Association, GalvInfo, Note 1.6, selecting coating thickness (read 2026-10-06)
- International Zinc Association, GalvInfo, Note 3.6, protection at cut edges and damage (read 2026-10-06)
- Steelscape, metallic coating summary (read 2026-10-06)
- ArcelorMittal Dofasco, Galvalume brochure (read 2026-10-06)
- ArcelorMittal Dofasco, Galvalume warranty (read 2026-10-06)
- McElroy Metal, what is the difference between galvanized and Galvalume (read 2026-10-06)
- McElroy Metal, technical bulletin on conditions corrosive to galvanized and Galvalume (read 2026-10-06)
- Tube & Pipe Journal, batch hot-dip and in-line galvanizing, by an AGA author (dated 2002-04; read 2026-10-06)
- Atkore, Gatorshield Plus galvanized steel tubing (read 2026-10-06)
- Wheatland Tube, mechanical tubing brochure (read 2026-10-06)
- Metals Depot, galvanized square tube (read 2026-10-06)
- Gibraltar Building Products, why the edges of a painted galvanized roof rust (read 2026-10-06)
- Gibraltar Building Products, Galvalume panel rust and washing near the coast (read 2026-10-06)
- American Galvanizers Association, damaged galvanized steel and storage (read 2026-10-06)
- American Galvanizers Association, when to repair scratches (read 2026-10-06)
- American Galvanizers Association, hot-dip galvanized steel in contact with treated wood (read 2026-10-06)
- American Galvanizers Association, touch-up and repair (read 2026-10-06)
- American Galvanizers Association, zinc corrosion rates for ISO 9223 categories (read 2026-10-06)
- Hot Dip Galvanizers Association of South Africa, Info Sheet 8, corrosivity of atmospheres (read 2026-10-06)
- Portland Bolt, galvanized coating lifespan FAQ, quoting the AGA (read 2026-10-06)
- City of Nowthen, Minnesota, planning packet with a planner's memo (dated 2019-03; read 2026-10-06)
- Ontario Ministry of Agriculture, Food and Agribusiness, factsheet 25-017 on corrosion of roof truss plates in farm buildings (dated 2025-06; read 2026-10-06)
- Xometry, gauge table for steel (read 2026-10-06)
Last verified: