How a steel can is protected from rust, and what each finish trades off.
Bare steel rusts, and a rusted fuel can contaminates its contents and eventually leaks. What keeps a steel container in service for years is the coating, inside and out.
Quick answer: What is the difference between galvanised steel and stainless steel?
Galvanised steel is mild steel with a zinc coat, which corrodes in place of the steel until it is used up. Stainless steel is an alloy with at least 10.5% chromium, whose oxide film heals itself when scratched. The US FDA Food Code keeps galvanised metal off food-contact surfaces used with acidic food, so galvanised cans carry fuel.
Steel corrodes when moisture and oxygen reach the metal. For a container that lives outdoors, on a tailgate or in a wash-down bay, unprotected steel has a short life. Protection is what makes steel viable. When you specify a steel can, you are specifying its coating, so treat that as the decision.
Iron oxidises wherever water and oxygen reach it, and the oxide that forms is porous and flakes away instead of sealing the surface. That is the difference from aluminium and stainless steel, whose oxides are dense, tightly bonded and stop the reaction within a few atomic layers. Rust exposes fresh metal to the air and lets the process run to the end of the material.
So protecting steel means one of two things: keeping the water and oxygen away from it, or giving the corrosion something it prefers to eat. Paint, powder and interior linings take the first route and fail the moment the film is breached. Zinc takes the second and keeps working after it is scratched. Knowing which route a finish uses tells you exactly how it will behave once the can leaves the warehouse and starts getting knocked about.
Galvanizing coats the steel in zinc, which resists corrosion and, where the coating is scratched, sacrifices itself to protect the steel beneath. It is a durable, low-maintenance finish suited to fuel and outdoor use. The zinc is also why a galvanized can is for fuel and not for food or water. Zinc can leach into what a can holds, and the US FDA Food Code keeps galvanized metal off food-contact surfaces used with acidic food.
Two processes carry the same word and are not interchangeable. Hot-dip galvanizing to ISO 1461 immerses the steel in molten zinc and grows a metallurgically bonded coating typically 45 µm to 85 µm thick. Continuously galvanized sheet to EN 10346 is thinner: a Z275 designation means 275 g/m² across both faces, about 20 µm a side. Electro-galvanizing to ISO 2081 is thinner again, often 5 µm to 12 µm on plated parts, and electro-galvanised sheet such as JIS G 3313 SECC carries about 1.4 µm to 5.6 µm a side. It buys you a very even surface that takes paint well rather than a long outdoor life.
The practical consequence for a buyer is that the word galvanized, on its own, covers finishes that differ by a factor of ten in service life. Ask which process and what coating weight, and get the answer written into the specification alongside the steel grade. A quotation that says only galvanized has told you nothing you can hold anyone to, and the difference between Z275 sheet and a hot-dip finish is visible in the price for a reason.
Zinc corrodes in preference to steel. Scratch a galvanized surface and the zinc around the mark gives up its own metal to keep the exposed steel clear of rust. Engineers call this cathodic, or sacrificial, protection, and it is the reason a galvanized can shrugs off the scuffs of daily handling. Paint behaves the other way. Chip a painted panel and you expose bare steel that starts rusting at once, with the rust then creeping under the film. That gap in behaviour matters most on a can that gets dragged, stacked and knocked.
Zinc sits at about −0.76 V on the standard potential scale against iron's −0.44 V, so where both metals are wet and connected, the zinc is the one that dissolves. The protection reaches sideways across the bare patch, which is why a scratch a few millimetres wide stays clean while the zinc either side of it slowly gives itself up. Nothing needs to flow over the damage or seal it. The steel is simply the wrong metal for the reaction to attack.
The limit is that sacrificial protection is consumed as it works, so the coating has a calculable life. ISO 9223 puts zinc loss at 0.7 to 2.1 µm a year in an ordinary urban atmosphere and 2.1 to 4.2 in a coastal or industrial one. On the seafront it is 4.2 to 8.4, and up to 25 where salt spray is constant. Run those against the coating weights above and a Z275 sheet finish gives a few years on a coastal site where a hot-dip coating on can-gauge sheet gives about five to twenty. That single calculation should drive the finish you specify, and the chart below runs it out.
It holds up in hard fresh water, in soil between pH 5.5 and 12.5 and in cured concrete, and it wears fastest in soft water, sea water and acid ground. In water, the chemistry sets the rate. The American Galvanizers Association (2020) puts zinc’s slowest corrosion between pH 5.5 and 12, rising sharply below pH 4 or above 12. Moderately hard and hard water, 60 to 180 ppm as calcium carbonate, forms protective scales on the zinc; soft water under 17 ppm is much more corrosive. Chloride is the most aggressive ion: 80 ppm in soft water causes severe corrosion, while hard water carrying 700 ppm may cause little or none.
Sea water takes zinc faster than salt air. The Galvanizers Association gives 10 to 15 µm a year for continuous immersion in UK waters, and the American Galvanizers Association about 25 µm in tropical seas. Heat changes the chemistry too. Above 60 °C, zinc may become cathodic to steel in some waters, so a damaged coating stops protecting the steel at the break (Galvanizers Association).
Buried, the soil decides. The Galvanizers Association names its pH, drainage, resistivity and whether it has been disturbed as the main factors, rates pH 5.5 to 12.5 as favourable and singles out soils containing ash and clinker as harmful. It suggests a thicker coating for buried work. The zinc a coating loses goes into the ground beside it, with the trace of lead the zinc carries. A 1993 survey of soil at transmission towers up to 29 years old, reported by the American Galvanizers Association, found lead above background only at the tower base. The level was below a fifth of the 500 µg/g the US EPA uses to decide on a clean-up. The survey found little sideways movement.
Concrete is the gentler case. While fresh concrete cures, calcium hydroxide in the wet mix reacts with the zinc to form calcium hydroxyzincate and hydrogen, and the reaction stops within a few days as the concrete sets (American Galvanizers Association, 2001). The same paper advises avoiding wet mixes above pH 13.3 unless chromates are present. The Galvanizers Association says galvanised steel can be safely embedded in concrete, and that damp mortar, cement and plaster etch the zinc slightly only while they set. None of this turns a galvanised can into a water can: ours carry fuel, for the reasons in food-contact and water certification, and other liquids are covered in the chemical compatibility guide.
A painted or powder-coated body adds corrosion resistance and colour. Powder coating to a RAL colour is the durable option, and it is how a private-label steel can carries a house colour. Powder bonds as a thicker, harder film than wet paint, so it resists the chipping that starts corrosion, which is why it is the sensible choice when a can carries your name.
Powder cures to around 60 µm to 80 µm in a single pass where a wet coat lands nearer 25 µm to 40 µm. The cured film is a crosslinked thermoset rather than a solvent-dried one, so it takes an impact by deforming instead of shattering. What decides whether it stays on, though, is the pretreatment underneath. Degrease, phosphate and rinse properly and the film holds for years; skip a stage to save cost and it lifts in sheets from the first stone chip.
Put powder over zinc and you get more than the sum of the two. The paint keeps water off the zinc so the zinc corrodes slower, and the zinc stops rust creeping under the paint where it is chipped. The American Galvanizers Association cites European studies that give this duplex system 1.5 to 2.3 times the life of the two coatings added together. For a private-label can that carries a house colour into a coastal market, that is the specification to write.
Clean the zinc, roughen it where it is smooth, and use a paint or powder made for galvanised steel. New zinc carries loose particles of zinc oxide and hydroxide that dissolve in water, and a coating laid over them can lift as they come away (American Galvanizers Association, Duplex Systems, 2012). The finished patina is an insoluble film bonded tight to the zinc, and paint grips it once it is clean. ASTM D7803 says that conversion can take up to two years.
Most painting falls in the awkward window, between 48 hours and a year after galvanising. Ask the galvanizer not to water-quench or chromate-quench work you will paint, because both can weaken the bond. Three ASTM documents split the preparation by product: D6386 for paint on hot-dip galvanized articles, D7803 for powder on the same articles, and D7396 for new sheet galvanised on a continuous line, which D6386 excludes.
A smooth, bright zinc surface needs a mechanical profile. The Hot Dip Galvanizers Association Southern Africa sets sweep blasting at no more than 3 bar nozzle pressure, a nozzle angle of 60 to 90° and a distance of 500 to 600 mm. It asks for non-metallic grit of 0.2 to 0.8 mm, used once. Full blast cleaning, as used on mild steel, damages the zinc layer.
Powder needs one more step. Gas trapped during galvanising escapes as the powder cures, and ASTM D7803 warns that unless outgassing drives it off before the bake, it leaves pinholes or blisters through which chlorides reach the zinc. Our galvanised cans take a RAL powder coat for private label, which makes them the duplex system described above.
The inside matters as much as the outside, and the two are separate jobs. Galvanizing or powder protects the outside; the inside needs its own lining, and a fuel can needs both. A hydrocarbon-service internal coating protects a fuel can's interior and is specified for the contents, not applied generically. The wrong interior is the most common failure in a cheap can, because the shell can look sound while the fuel attacks the wall you cannot see.
Ask about the interior at enquiry: "what is the lining and how is it applied". A named system with a stated film thickness is an answer. "Coated" is not. Interior coatings are where cost is quietly removed from a cheap can: the outside carries the appearance and the inside carries the service life, and only one of those is visible on a sample.
Coatings are thinnest on edges, welds and the neck, because the film pulls back from a sharp corner and a weld bead, so those spots rust first; check them before the flat panels. Keep coated steel dry in storage, and inspect for chips and corrosion between uses. Rinse off salt and mud after a trip, and let the can dry before you put it away. A small coating repair extends a can's life; ignored, a chip becomes a rust spot and then a leak.
Touch up galvanized steel with a zinc-rich paint rather than an ordinary one, because the repair has to restore the sacrificial protection and not just cover the mark. An ordinary topcoat over bare steel on a galvanized body seals moisture against the metal at the one place the zinc is already gone, which is why a cosmetically tidy repair can corrode faster than the untouched chip.
White rust, or wet storage stain, is a white or grey powder of zinc oxide and zinc hydroxide that forms on new galvanised steel kept damp without air. In open air, the thin oxide film that forms as the steel leaves the zinc bath reacts with carbon dioxide into a zinc carbonate patina (Galvanizers Association, HDG Datasheet 11). Water trapped between nested or stacked parts shuts the carbon dioxide out, and the hydroxide keeps growing for as long as the surface stays wet. Chlorides from sea spray or road salt speed it up (American Galvanizers Association, 2014).
The stain looks worse than it is. Its powder takes up three to five times the volume of the zinc it consumed, and a light dusting has no discernible effect on coating thickness. The Galvanizers Association reads EN ISO 1461:2022 as giving no grounds for rejection unless the stain has thinned the coating by a large margin, so measure the zinc before you reject a delivery. Stain that has turned black means much of the zinc is gone, and the American Galvanizers Association then calls for stripping and regalvanising.
Prevention is airflow and drainage, from the galvanizer’s yard to your store:
In transit, a tarp over spaced stock keeps rain off, and the American Galvanizers Association advises a drying agent in any sealed container. A plastic film laid tight on the zinc does the opposite and traps sweat. Galvanised sheet can leave the mill passivated, oiled or both (codes C, O and CO in thyssenkrupp’s EN 10346 range), which guards against the stain. The American Galvanizers Association warns that such post-treatments may interfere with paint and powder adhesion, so tell the mill or the galvanizer when the zinc will be coated.
Two errors ruin a good can. The first is filling a galvanized or coated steel can with drinking water or food, when neither the zinc nor the coating was made for food contact; a water can needs a food-contact specification, covered in food-contact and water certification. The second is ignoring the interior spec and ending up with rust in the fuel. Match the coating to the contents and neither happens.
The version that catches good buyers is a can moved between duties rather than specified wrongly at the start. A container bought for water and later filled with a solvent has a perfectly correct interior for the job it was bought for and the wrong one for the job it is doing. Mark cans by contents at the point they enter service, not at the point somebody remembers, because the reassignment is what breaks the specification rather than the purchase.
Galvanised steel is mild (carbon) steel with a zinc coat, and plain mild steel is the same metal left bare. Stainless steel is an alloy with at least 10.5% chromium and no more than 1.2% carbon, the EN 10020 definition as DIBt states it. The zinc corrodes in place of the steel; the chromium forms an oxide film that heals itself.
Zinc corrodes too, at a small fraction of the rate of steel. ISO 9223 puts zinc’s first-year loss in an urban C3 atmosphere at 0.7 to 2.1 µm, as the American Galvanizers Association tabulates it, and BS EN ISO 12944-2 puts low-carbon steel at 25 to 50 µm (SteelConstruction.info). On a coast with high salinity, category C5, the figures are 4.2 to 8.4 µm against 80 to 200 µm. Bound for bound, from C3 to C5, bare steel loses 19 to 36 times as much metal, and the American Galvanizers Association puts weathered zinc at about a thirtieth of the rate of steel in the same place.
| Property | Galvanised steel | Stainless 304 | Mild (carbon) steel |
|---|---|---|---|
| How it resists rust | Zinc corrodes first and protects a scratch | A chromium oxide film re-forms when scratched | It does not; paint or a lining does |
| First-year loss, C3 | 0.7–2.1 µm of zinc | No ISO 9223 rate; chlorides can pit it | 25–50 µm of steel |
| Appearance | Bright when new, matte grey as the patina forms | Metallic finish set at the mill | Dark grey, red-brown once it rusts |
| Welding | Zinc burns off the seam and the fume needs extraction; repair with zinc-rich paint | Welds; the L grades suit welded, corrosive duty | Welds with no coating in the way, then needs paint |
| Painting | Needs zinc-specific preparation, above | Needs no paint | Paint is its only outside protection |
| Food and drinking water | FDA Food Code 2022, 4-101.15: not for food-contact surfaces used with acidic food; WHO: zinc tastes astringent from about 4 mg/l in water | Our water cans use it across the wetted path | Needs a lining: Food Code 4-101.11 asks for corrosion-resistant food-contact materials |
The contents choose between them. Our horizontal galvanised can (0.6 mm, or 0.7 to 0.8 mm in the heavier build) and 20 L fuel tank with spout (0.8 mm) are fuel cans, bare galvanised inside or lined for jet fuel. Both list acids, alkalis, food and drinking water as unsuitable. Check any other liquid in the chemical compatibility guide. For salt air, read stainless 304 vs 316 and marine fuel and water containers. Most NATO pattern cans are lined cold-rolled steel with zinc or powder outside. Grades and gauges are in steel grades for containers, and the non-steel bodies in steel vs HDPE and aluminium vs steel.
Stainless steel resists corrosion because its chromium forms a transparent, chromium-rich oxide film that re-forms by itself wherever air or aerated water reaches the surface. EN 10088-1 sets the floor at 10.5% chromium and no more than 1.2% carbon (Euro Inox, Pickling and Passivating Stainless Steel, 2007). Aluminium protects itself the same way, as aluminium vs steel fuel cans explains. Molybdenum and nitrogen strengthen the film against chlorides, and the British Stainless Steel Association (BSSA) ranks grades by PREN, the pitting resistance equivalent number: %Cr + 3.3 × %Mo + 16 × %N.
The BSSA prints each range from the lowest and highest composition the standards allow, and warns that PREN ranks grades without predicting whether one suits a given duty. The typical values in stainless 304 vs 316, 18 to 20 for 304 and 24 to 26 for 316, sit inside these ranges.
| Grade | EN number | Type | PREN | Corrosion resistance |
|---|---|---|---|---|
| 430 | 1.4016 | Ferritic, 16–18% chromium | 16.0–18.0 | Good indoors; needs frequent cleaning in harsher air. Resists stress corrosion cracking |
| 303 | 1.4305 | Austenitic, free-machining, 0.15–0.35% sulphur | 17.0–20.8 | Mildly corrosive environments; remove sulphides after machining |
| 304 | 1.4301 | Austenitic, 17.5–19.5% chromium, 8–10.5% nickel | 17.5–20.8 | Urban and rural air, foods and beverages |
| 304L | 1.4307 | 304 with carbon held to 0.030% | As 304 | As 304; resists sensitisation in welded medium and heavy sections |
| 316 | 1.4401 | Austenitic, 2–2.5% molybdenum | 23.1–28.5 | Better against pitting and crevice attack in chlorides |
| 316L | 1.4404 | 316 with carbon held to 0.030% | 23.1–28.5 | As 316, for welded medium and heavy sections |
| 2205 | 1.4462 | Duplex, 21–23% chromium, 2.5–3.5% molybdenum | 30.8–38.1 | Severe marine exposure |
PREN from the BSSA. It does not list 303, so that range is worked out the same way from the EN 10088-1 limits in Euro Inox’s tables (2007); 304L shares 304’s chromium and nitrogen limits. Service notes from Acerinox (430), Marcegaglia (303, 304, 316) and ASSDA (304 to 2205).
PREN leaves out the sulphur that makes 303 easy to machine. Marcegaglia rates its 303 for mildly corrosive environments and advises a chemical treatment on every part to strip sulphides from the finished surface. Grade 430 has no molybdenum in its specification; Acerinox finds it good indoors and calls for frequent cleaning in harsher air to keep stains off. The L grades matter where heat of 450 to 850 °C, as in welding medium or heavy sections, would otherwise precipitate chromium carbides at the grain boundaries; without that, ASSDA finds standard and L grades usually identical in corrosion resistance. Our 20 L stainless water can is 304 across the wetted path, and the grades behind each body are in steel grades for containers.
Where stainless does corrode, the attack is local. Euro Inox describes pitting and crevice attack in small areas starved of oxygen: mechanical joints, tight corners and incomplete or poorly finished welds. Heat tint, the coloured oxide beside a weld, leaves a surface layer low in chromium until it is pickled off. On the coast a brown film called tea staining builds up; ASSDA cites a finish no rougher than 0.5 µm Ra and suggests washing the steel whenever nearby glass needs washing. A brown bloom or rusty scour marks after installation often come from carbon steel particles left on the surface, which the ferroxyl test in ASTM A380, 7.3.4, detects. Strong hypochlorite attacks 304 as well, which is why our cleaning guide rinses it out of stainless cans.
Where corrosion protection is a burden, stainless steel and HDPE avoid it entirely. Read steel vs HDPE and stainless 304 vs 316.
Each of those trades the coating problem for a different one rather than removing it outright. Stainless removes the liner and brings a chloride-pitting question and a higher price. HDPE removes corrosion altogether and brings permeation and a five-year dangerous-goods life. Coated steel keeps both problems and is the cheapest and toughest body of the three. Each option has a cost. Pick the one whose cost your duty cycle can bear.
Fortitude21 galvanizes steel cans for fuel, powder-coats them to a RAL colour for private-label runs, and specifies the interior lining to what the can will hold. Tell us the contents and where the can will live, and we match the coating inside and out to that job.
Coating follows the contents and the exposure.
| Your use case | Recommended can | Why this one |
|---|---|---|
| Galvanised for outdoor fuel duty |  Horizontal Galvanised Can — 5L / 10L / 20L |
Sacrificial zinc resists rust and scuffs. |
| Coated steel fuel can |  20L NATO Steel Fuel Can |
Galvanised outside, hydrocarbon-lined inside. |
| No coating to maintain |  Stainless NATO Can — 10L / 20L |
Stainless avoids the corrosion problem entirely. |
| Water, where zinc is unsafe |  20L Stainless Steel Water Can |
AISI 304 stainless, food-grade across the wetted path. |
Hot-dip immerses the steel in molten zinc, giving a thick, metallurgically bonded coating that lasts far longer outdoors. Electro-galvanizing deposits a thin, even zinc layer electrically, giving a better surface for painting but much less corrosion life. Jerry cans in field service want hot-dip or an equivalent coating weight.
No. Stainless resists corrosion through its own passive chromium oxide layer, which repairs itself when scratched. That is the practical advantage over coated steel: a deep scratch on a coated can starts rust, while the same scratch on stainless does nothing.
Because water collects at the base and the internal coating is hardest to inspect. Condensation from temperature cycling, or water absorbed by an ethanol blend, settles under the fuel and attacks any coating defect. Storing cans full, and draining fully before long storage, both reduce it.
Yes. Galvanised steel is carbon steel with a zinc coat, so it is a ferrous metal and a magnet holds to it through the zinc. The Australian Stainless Steel Development Association gives mild or carbon steel a ferritic structure with a relative permeability of at least 200. Austenitic stainless such as 304 counts as non-magnetic when annealed but attracts a magnet where it has been cold worked, so a weak pull at a pressed corner can still be stainless.
Only a little in air. On the Galvanizers Association scale, where 0 means little or no extra corrosion of the zinc and 2 calls for protective measures, contact with aluminium rates 0 in rural air and 0 to 1 in urban, industrial and marine air. Immersed, it rates 1 in fresh water and 1 to 2 in sea water. Separate wet joints with plastic washers or spacers, and isolate large aluminium areas such as cladding.
Yes, in air. The Galvanizers Association rates stainless steel in contact with galvanised steel at 0 to 1 in rural, urban and marine air, and expects no bimetallic problem from stainless fasteners, whose area is small beside the zinc. It still names insulating washers as best practice. Immersed, the rating rises to 0 to 2 in fresh water and 1 to 2 in sea water, so isolate any joint that sits wet.
By dipping cleaned steel in molten zinc. The Galvanizers Association lists the stages: degrease, remove rust and mill scale in hydrochloric acid, dip in a flux of zinc and ammonium chloride, dry, then immerse in molten zinc. The bath runs at 440 to 460 °C, against a melting point of 419 °C. The zinc reacts with the steel to form zinc-iron alloy layers under a layer of near-pure zinc. Long runs of sheet, wire and tube go through automated lines outside EN ISO 1461.
Yes. The Galvanizers Association says steel and zinc are recycled together in the established steel recycling processes, and the zinc goes back to zinc production without loss of properties, then into galvanising again. Galvanised parts can also be reused with their coating in place, or regalvanised at the end of their design life and returned to the same use.
Often you need not. The American Galvanizers Association says light and medium white rust weathers into the normal zinc patina once air reaches it. Where it must go, the Galvanizers Association suggests a stiff brush with a dilute acidic or ammonia solution, then a fresh-water rinse and full drying. Measure the zinc thickness left afterwards. Black stain means so much zinc has gone that the steel needs stripping and regalvanising.
Yes, sheet made for forming bends and presses. The steelmaker thyssenkrupp says every common cold-forming process works on its hot-dip galvanised sheet to EN 10346 when the die geometry and surface suit it, and the die must be smooth so it does not wear the zinc off. The zinc also lowers friction, to a coefficient of 0.08 to 0.12 against 0.14 to 0.18 for uncoated sheet, so blank-holder settings may need changing.
Yes. The zinc coat and the steel under it are both metals, and both carry current. The steelmaker thyssenkrupp notes that the zinc gives galvanised sheet a lower contact resistance than uncoated cold-rolled sheet, which is why resistance spot welding it needs a higher current and electrode force. Stainless steel conducts as well: Euro Inox, quoting EN 10088-1, gives grade 1.4301 (304) an electrical resistivity of 0.73 Ω·mm²/m at 20 °C.
The steel grade under the zinc sets it. Hot-dip galvanised sheet in the common forming grade DX51D to EN 10346 has a tensile strength of 270 to 500 MPa, about 39 to 73 ksi (Nippon Steel Slovakia). Structural grades carry their minimum yield in the name: S350GD yields at 350 MPa or more and reaches at least 420 MPa in tension, about 61 ksi (Salzgitter Flachstahl). Ask for the steel grade as well as the coating weight.
Usually a trace. The American Galvanizers Association says zinc used for galvanising contains up to 1% lead, because lead occurs in most natural zinc deposits. In its study the finished coating held 25 to 75% of the bath’s lead level, 50% on average, as small particles in the outer layer of free zinc. A bath of High Grade zinc in the same study held 0.022% lead, so the zinc a galvanizer buys sets how much lead reaches the coating.
Less so than 304. Grade 301, 1.4310 in EN 10088-1, allows 16 to 19% chromium and 6 to 9.5% nickel, against 17.5 to 19.5% and 8 to 10.5% for 304, as Euro Inox tabulates the standard. Worked out the British Stainless Steel Association way, its PREN floor is 16.0 against 17.5 for 304, so it ranks lower for pitting resistance. Keep it to mild, dry service and choose 304 or 316 where chlorides or standing water reach it.
Keep them apart. In the Galvanizers Association’s bimetallic table, contact with copper rates 1 to 2 in urban and marine air and 2 to 3 in sea water, on a scale where 3 means contact should be avoided. Brass rates 1 in urban air and 2 to 3 in sea water. The Association advises against using galvanised steel and copper together, strongly advises electrical isolation even in air, and warns that rain running off copper can deposit enough copper on the zinc to corrode it.
Yes. Acerinox describes 1.4016, the EN number for 430, as the base alloy of the ferritic group, and the Australian Stainless Steel Development Association lists ferritic stainless steels as magnetic. Austenitic 304 and 316 are generally non-magnetic when annealed but attract a magnet once cold worked, so a magnet cannot tell 430 from carbon steel or prove a pressed part is 304. An EN 10204 3.1 mill certificate settles the grade.
Partly: steel and its zinc coat both have recycling routes, but the coat is used up as it protects. The US EPA estimated that 70.9 per cent of steel cans were recycled in 2018, and the US Geological Survey reports that US smelters recover zinc from galvanising residues. ISO 9223 puts zinc loss at about 0.7 to 2.1 micrometres a year in an ordinary urban atmosphere, so a thicker coat gives a longer-lived can.
Yes, once the zinc is used up. The zinc corrodes first and protects the steel beneath, even across a scratch a few millimetres wide, but it is consumed as it works. ISO 9223 puts zinc loss at about 0.7 to 2.1 micrometres a year in an ordinary urban atmosphere and 4.2 to 8.4 on the seafront. That is why a thin Z275 sheet finish lasts a few years on a coastal site, where a hot-dip coating lasts about five to twenty.
Yes, and the combination outlasts either coating alone. The American Galvanizers Association cites European studies that give paint or powder over zinc 1.5 to 2.3 times the life of the two coatings added together. The paint keeps water off the zinc, and the zinc stops rust creeping under a chip. New zinc carries loose oxide and hydroxide, so clean it and roughen smooth zinc before coating, and repair chips with a zinc-rich paint.
No. Galvanised steel is ordinary steel with a zinc coating, and the zinc corrodes in place of the steel until it is used up. Stainless steel has no coating: it is an alloy steel with at least 10.5 per cent chromium, which forms a thin oxide film that repairs itself when scratched. Both are ferrous metals. The US FDA Food Code bars galvanised metal from food-contact surfaces used with acidic food, so galvanised cans carry fuel and stainless carries drinking water and food.
Steel sheet or coil zinc-coated on a continuous line before it is cut and formed, under EN 10346. Its coating is thinner than on an article hot-dip galvanised after fabrication to ISO 1461: a Z275 sheet carries 275 grams per square metre over both faces, about 20 micrometres a side, against 45 to 85 micrometres. Ask a supplier which process a can or pallet uses, and the coating weight, because service life differs several times over.
Edges are where it rusts first, though not at once. Cutting or drilling leaves bare steel at the edge, and the zinc beside it protects a narrow strip sacrificially, the same way it keeps a scratch a few millimetres wide clean. That protection uses the zinc up faster at the edge. Touch up cut edges and holes with a zinc-rich paint, because an ordinary topcoat seals moisture against the bare steel.
Steel ones do once their protection fails. Aluminium and stainless cans form a dense oxide that stops the reaction, so they do not rust the way bare steel does. A steel can depends on its finish: galvanizing gives up zinc to keep a scratch clean, while paint and powder keep water off until they chip. Rust starts at edges, welds, the neck and the inside base where water settles, so check those first and touch up chips with zinc-rich paint.
Yes. Galvanised sheet is carbon steel with a zinc coating: ISO 3575 covers it as continuous hot-dip zinc-coated carbon steel sheet. The steel carries the load and the zinc protects it, corroding in preference to the steel wherever the coating is scratched. Stainless steel is a different alloy. It resists corrosion through its own chromium oxide layer, so it needs no zinc and no paint.
Yes, with fume control. HSE links metal fume fever, a flu-like illness, mainly to welding or hot work on galvanised metal. It expects engineering controls such as local exhaust ventilation for welding indoors, with respiratory protection where extraction alone does not control exposure. The weld itself carries no zinc, so restore the protection with a zinc-rich paint. An ordinary topcoat over bare steel seals moisture against the metal and can corrode faster than an untouched chip.
SPCC is the grade symbol in the Japanese standard JIS G 3141 for cold-reduced carbon steel sheet for general use, the basic commercial grade; SPCD and SPCE are the drawing and deep-drawing grades. SPCC is bare carbon steel, so it rusts wherever moisture and oxygen reach it. A container pressed from it needs zinc, paint or powder outside, and a lining specified for the contents inside.
Yes. SPCC is a grade of cold-reduced carbon steel sheet under the Japanese standard JIS G 3141, and it is bare carbon steel, with no zinc coating and none of the chromium that protects stainless. It rusts wherever water and oxygen reach the metal, and the rust flakes away to expose fresh steel. A container pressed from cold-rolled sheet relies on galvanising, paint or powder coating outside and a lining inside.
The standards and regulations this page relies on, at their issuing body. Where a market rule is named here, check the current revision before you specify against it.
Last reviewed by David Guru, Co-Founder & Business Development Director.
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