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Stainless Steel Foil — Gauge, Grade and Tolerance Selection
The material we refer to as stainless steel foil is cold-rolled stainless supplied below approximately 0.20mm – just thin enough that only a few grains traverse the thickness and sheet-metal rules don’t really apply. ASTM A480/A480M provides general requirements for stainless plate, sheet, and strip but does not offer separate terminology for foil. Consequently, two mills can simultaneously quote same product of 0.1 mm for 304 stainless steel foil based on their internal rules and be considered correct in each respective response.
0.0005–0.020 in
Decimal band this page covers
(0.0127–0.508 mm)
A480 / ISO 9445
Tolerance frameworks you can hold a mill to
10 grades
201 · 301 · 304 · 304L · 316 / 316L · 321 · 309S · 310S · 430 · 2205
EN 10204 3.1
Certificate type to name in the purchase order
N = 4.4–8.9
Grains through thickness in commercial 0.1 mm 316L
20-high mill
Cold-rolling class that reaches foil gauge
Why Thin-Gauge Stainless Sourcing Goes Wrong — The 0.2 mm Problem
A shipment of thin stainless rarely is turned away because of chemistry. Often the problem is that the mill and customer worked from different definitions for the same word and no one documented it on the purchase order. That’s the practical implication of our 0.2 mm Problem.
Start here: the standard does not define foil
“ASTM A480/A480M-23b, General Requirements for Flat-Rolled Stainless and Heat-Resisting Steel Plate, Sheet, and Strip”‘s Scope clause 1.1 refers to A240/A240M, A263, A264, A265, A666, A693, A793 and A895 flat-rolled stainless steel. Foil is not one of the types of products it specifies.
Three things go wrong once material crosses that line:
- For instance, tolerance charts break down. Thickness tables that are applicable to sheet and strip can be on a different scale entirely than those required for, say, 0.02 mm and finer.
- An order that says nothing more about temper than grade leaves annealled, half hard, and full hard all within compliance.
- Even edge finish can become a crucial manufacturing specification. The slight burr that was cosmetic on 2mm material will be functionally catastrophic on foil-sized material, creating stacked issues or shortages.
Our Solution: Order By Specifications.
We quote based on precise dimensions. Every inquiry is specified according to exact thickness, width, temperament and tolerance so the term “foil,” is never forced to carry the entire specification alone.
The reason we do that is that all of our precision cold rolling, annealing and inspections take place in one, ISO 9001 certified, facility; meaning TiAlloy engineers can verify a 0.05mm specification with realistic mill capabilities before issuing pricing. Production purchasers will receive the same consistent result regardless of where that specification Falls, eliminating the potential for a first-time purchase ending up as a complaint.
Not sure whether your part is foil or strip under your own standard?
Download the Foil Gauge Map PDF and check the boundary against your drawingThe Foil Gauge Map — Inch, Millimeter, Micron and Sheet Gauge
North America usually asks for foil to be made in decimal inches, while Europe and Asia prefer millimeters and researchers and coaters commonly use microns. These are the three different measurement scales that describe the same material, and confusing them on the initial order is not uncommon. This chart is published here so that it can be compared against a drawing before it’s sent to any potential supplier.
| Decimal (in) | Millimeter | Micron (µm) | Typical duty at this gauge |
|---|---|---|---|
| .0005 | 0.0127 | 12.7 | Vapor-deposition and research substrate |
| .0007 | 0.0178 | 17.8 | Ultra-light shielding and barrier layers |
| .001 | 0.0254 | 25.4 | Metal domes, diaphragms, strain-gauge carriers |
| .002 | 0.0508 | 50.8 | Heat treating tool wrap; light stampings |
| .0025 | 0.0635 | 63.5 | Precision spacers and reed components |
| .003 | 0.0762 | 76.2 | Gasket carriers; fine etched parts |
| .004 | 0.1016 | 101.6 | Fuel-cell bipolar plate stock; heat-exchanger fin |
| .005 | 0.1270 | 127 | Shim stock; formed seals |
| .006 | 0.1524 | 152.4 | Deep-drawn cans and cups |
| .007 | 0.1778 | 177.8 | Spring clips and retainers |
| .008 | 0.2032 | 203.2 | General shim and leveling stock |
| .009 | 0.2286 | 228.6 | Formed brackets in thin gauge |
| .010 | 0.2540 | 254 | Strip-adjacent; slitting behaves like thin sheet |
| .012 | 0.3048 | 304.8 | Light structural stampings |
| .014 | 0.3556 | 355.6 | Clamp bands and hose ferrules |
| .015 | 0.3810 | 381 | Thin sheet territory |
| .016 | 0.4064 | 406.4 | Thin sheet territory |
| .020 | 0.5080 | 508 | Thin sheet territory |
Direct answer — is 20 gauge thicker than 22 gauge?
Yeah. Actually, with that in the stainless sheet gauge the smaller the number is, the thicker the material; 20 gauge is 0.0375 inches (0.95 mm) and 22 gauge is 0.0312 inches (0.79 mm).
For the foil buyer, even more importantly than there being a smaller number indicating a thicker material, it’s that the foil gauge runs out in number long before sheet ends. The gauges for stainless sheets stop around 0.0125-in (30 gauge) which is still five times thicker than 0.0025 inches and that’s why every foil order we ever get is referenced in decimal form instead of gauges.
Two different styles come off the samecoil:continuousrolls are manufactured for use on continuous stamping and etching lines, while the flat stainless steel sheet is supplied as blanks typically up to 300 mm x 300 mm for laboratory, prototype and short production runs.
We frequently hear stories of drawings showing 0.1 mm, whereas the order is written up in 0.004-inches (an approximation only, after tolerance). Our engineers will always restate the specification in both units before accepting any enquiry and the ISO 9001 record provides confirmation of any delivered product’s dimensions in both millimeters and inches to avoid post-production quibbling over whether a 0.1016-mm delivery is acceptable for a stated requirement of 0.1 mm.
Working with three measuring systems on a single drawing?
Download a printable PDF chart of our Foil Gauge Map →Foil Grades, Tempers and Surface Finishes — Product Selection
Buyer focus, and procurement should match.
Like with thicker plates, the grade choice for foil in gauge is based on corrosion and temperature exposure ratings, but one factor is added to that decision making: How much cold working will the part require? For instance, a grade that can be annealed without complications and work-hardened reliably will be more valuable for a 0.05-mm (0.002-in) application than a grade with a somewhat better published rating for corrosion resistance.
Because 300-series austenitics work-harden readily at high reductions, without fracturing, they have long been the preferred choice when rolling metal for foil applications; 304, however, is the most commonly-used stainless steel in any sheet form, and the addition of titanium to 321 and niobium to 347 stainless provides enhanced resistance to hot environments.
Temper is half the specification
Cold working causes a reduction in elongation combined with increased strength and a substantial difference in these two factors exists between any two different tempers of the same grade at foil gauge. If an order is placed without specifying a temper, the most critical material characteristic will have been left up to chance. Most Published mechanical properties always include a temper specification for this very reason.
| Condition | What it is | Order it when |
|---|---|---|
| Annealed (soft) | Fully recrystallized after final pass | Deep drawing, bending, forming to a radius |
| Quarter hard | Light cold reduction retained | Mild forming with some stiffness needed |
| Half hard | Moderate cold reduction retained | Flat parts that must resist handling damage |
| Full hard | Maximum cold reduction, minimal ductility | Shim stock, flat springs, blanked parts |
| Spring temper | Highest reduction, grade-dependent (301) | Reeds, clips, components that must return |
Surface finish changes what the part can do
A mirror-bright surface with no visible signs of oxide can be achieved through bright annealing under protective atmosphere, eliminating both the need for pickling and its accompanying dull oxide layer typically associated with 2B and 2D surfaces. Surface characteristics may be specified on each of the four major stainless steel groups, along with any other criteria you desire.
“On foil we quote three things before price: the decimal thickness, the temper, and what the customer is going to do to the material afterwards. Two of those get left off most enquiries, and that is where the rework comes from.”
— TiAlloy Engineering Team, flat-rolled productsWe manufacture flat-rolled stainless from melting through rolling and annealing in one plant, with the manufacturing chain running from vacuum induction melting, vacuum arc remelting and electroslag remelting on the front end and bright annealing, solution annealing and pickling-passivation lines on the back end. Foil-gauge cold rolling runs on multi-high mill stands, the same 20-high configuration named in the published rolling art for precision stainless strip. Where a grade sits outside the foil band we will say so at enquiry rather than at delivery.
Picking the highest-alloy grade is not always the right call. Unlike a plate application, where the corrosion number usually decides, a foil part is often limited first by how the material behaves through the last rolling pass, and the trade-off between corrosion margin and formability has to be made deliberately.
If your requirement sits above the foil band, the same grades are available as stainless steel coil and plate – see how plate and sheet tolerances change once you leave the foil band.
Comparing 316 stainless steel foil against 304 for a chloride duty?
Request a free sample swatch set in both grades →Thickness Bands and Tolerance — What “Tight Tolerance” Actually Means
The Four Thickness Bands
There are 4 bands that span the working range and in each of the bands a different criterion dictates acceptance. The Four Thickness Bands below have been extracted from established tolerance standards, and also from actual cold roll mill hold capability and are therefore universal.
Strip-adjacent. Published strip tolerance tables still track reality; slitting and shearing behave close to thin sheet. Most heat-exchanger and gasket work sits here.
True foil. Size effects are active for common annealed grades. Temper and grain condition drive acceptance more than the thickness figure does.
Sub-50 micron. Flatness, coil set and edge burr become functional defects rather than cosmetic ones. Handling damage starts to rival rolling accuracy.
Ultra-thin. Grain orientation dominates the mechanical response. Specify by end-use performance, not by a thickness figure alone.
A peer-reviewed study of five industrial stainless steel foils from different suppliers, all at 0.1 mm thickness, measured grain sizes from 11.2 m to 22.5 m. That gives a thickness-to-grain-size ratio (N = t/d) between 8.9 and 4.4 – a two-fold spread across nominally identical material.
Grain-specimen size effects begin once N falls below about 15, and certainly below 10. Every one of those five commercial foils was already inside that zone, which means forming behavior was being governed by something the grade and the thickness tolerance never disclosed.
With four to nine grains through the thickness, the response of the sheet stops being an average and starts depending on how individual grains happen to be oriented. That is why two lots that both pass a thickness check can behave differently in the same die. Consistent grain condition from lot to lot, not the tolerance figure alone, is what turns product consistency into supply reliability.
The other study that used the same research finds results that challenge an old habit from when we worked with sheets: forming limits for 304 foil actually improved with annealing, even though the ratio between thickness and grain size decreased from 7.5 to 2.4. In other words, finer grain size isn’t always better, at least within the foil band.
Machinists that have work with the material characterize the failure modes very simply. You know, I’ll just pull this up verbatim. You read what they say, and it just plain and simple.”
- The only thing you have an issue could be some debris on stock on of stainless when cutting down ordered material
- There is sheer lips on it already – this stock has got to be flattened out before it’s usable.
- I cut and use tons of thin little shims for the parts and there are going to be tons of the small ones for that, I’m saying like 60 per shift, depending on the occasion.
- 0.1mm metal thickness – impossible? I am going crazy with what I think it should be a straightforward ask – to source the band in the first place.
The four that have these are complaint as I previously stated all chemistry related edge and flatness issues rather than chemical in nature. The practical reason that a foil order requires an edge is.
Condition of the slit edge and the Coilset and flatness must be placed orderwise as thickness dimension. We quote these items with line items, as items these need to be audited.
In fact, tighter is not better, which is the trade-off worth calling out explicitly. If you make a class tighter than the required standard table accept a class will require more careful controlling and you will increase rejecting rate. That is why TiAlloy engineers will suggest if a tight control over an accept a given class will require a precision which the piece does not. Indeed, our ISO 9001 inspection chart reveals exactly the same 0.005 mm acceptance.
What to write instead of “tightest tolerances”
State name of tolerance scheme, namely ASTM A480/A480M or EN ISO 9445, nominal thickness as a decimal, width and slitting type, tempers required and allowed edge condition. Five such listed parameters are better than one adjective, and will cause both sides to stand at something your micrometer will determine. If a specific dimension is required to be classified beyond that contained within the standard table, advise at enquiry to cause a reject or accept boundary to be drawn prior to quoting instead of after delivery.
Foil, Strip or Thin Sheet — and When Aluminum Is the Wrong Answer
Before a grade is even considered, the following two questions would have to be answered. Should this be foil in the first place? Should this be stainless at all? Any miss-step made in answering those would lead to a cost-ly screw-up since the part will likely be tooled up before the material specification can be double checked.
steel foil vs aluminum foil is that Steel is selected on cost and weight and the assembly runs at 300C – aluminum is selected, loses the material strength properties long before 660C melting temp – steel with a specification minimum tensile stress of 515MPa, tested to ASTM and ISO standards, has a minimum tensile property of 515MPa at 300C. This is a classic example of a job where the engineers are choosing based on price not engineering.
| Property | 304 stainless foil | 316L stainless foil | Commercial aluminum foil |
|---|---|---|---|
| Tensile strength, min | 515 MPa | 485 MPa | ~90 MPa (1100-O) |
| Yield strength, min | 205 MPa | 170 MPa | ~35 MPa (1100-O) |
| Elongation, min | 40 % | 40 % | ~35 % |
| Density | 7.9 g/cm³ | 8.0 g/cm³ | 2.70 g/cm³ |
| Melting range | 1400–1455 °C | 1370–1400 °C | ~660 °C |
| Chloride pitting resistance | Moderate | Raised by 2–3 % Mo | Poor in salt service |
However, aluminum foil wins from weight and for cost per m 2, but loses everything above a few hundred degrees. Whether a barrier has to stand furnace, exhaust or steam service, the melting range alone determines the answer. Copper and brass foil are selected for their conductivity, not for corrosion resistance, and answer yet another question.
Metal Foil General is machine shop consumable and production consumable at the same time as a engineering material, that is why the wrong decisions have come to surface at late stages. TiAlloy engineers perform the substitution check against the temperature of the application and chloride content before we even provide a quote, on precisely machined tooling as we do for the inspected coil that we will deliver.
Foil or slit strip Which one comes out on top? is determined by the width and what follows the width.
- Consider foil when the component thickness is below 0.20 mm, especially for stamping, etching, wrapping or laminating processes.
- Use a split strip if thickness exceeds 0.20 mm or if a rounded edge is to be made before coiling / winding.
- Use thin sheet for a single section if it’s handled on its own and flatness of panel as a whole is best to maintain it.
Considering a stainless-for-aluminum swap on a hot-side part? Send the drawing for a feasibility check against the service temperature
Shoot the drawing over to check feasibility at your service temp, and see what tollerance you needWhere Stainless Steel Foil Is Used — Application-to-Grade Routing
Acceptance criteria are changing more dramatically between applications than the list of grades would imply. A gasket carrier and a bipolar plate can be cut from the same 0.10 mm 316L and rejected for completely different reasons. The material occupies a space between consumer and industrial use, while the demand for the thinner bands is being pulled by battery, medical and hydrogen programs.
| Application | Grade | Gauge band | What governs acceptance |
|---|---|---|---|
| Heat treating tool wrap | 321, 309S | 0.05 mm (.002 in) | Service temperature ceiling; airtight fold; single use |
| PEM fuel cell bipolar plate | 316L | 0.075–0.11 mm | Formability at channel corners; interfacial contact resistance |
| Battery can and pouch barrier | 304, 316L | 0.02–0.10 mm | Electrolyte compatibility; coating adhesion |
| Heat exchanger and condenser fin | 304, 316L, 2205 | 0.08–0.20 mm | Corrosion in service water; brazing or welding response |
| Food-contact packaging and equipment | 304, 316L | 0.05–0.20 mm | Surface cleanability; hygienic joint design |
| Gaskets, seals and spacers | 304, 316L, 321 | 0.05–0.20 mm | Compression set; edge burr; flatness under bolt load |
| Shim and leveling stock | 304, 316L | 0.025–0.51 mm | Thickness repeatability lot to lot; clean shear |
| Automotive exhaust and sensor components | 321, 430, 409 | 0.05–0.20 mm | Thermal cycling; oxidation resistance at the hot end |
| Electromagnetic shielding layers | 430, 304 | 0.01–0.05 mm | Continuity of the layer; magnetic behavior of the grade |
| Precision stampings and metal domes | 301, 304 | 0.01–0.10 mm | Temper consistency; spring return; grain condition |
| Catalytic converter substrate | Ferritic high-Al types | 0.03–0.05 mm | Oxidation resistance through thermal cycling |
| Flexible display and solar substrate | 304, 316L | 0.02–0.10 mm | Surface roughness; rolling-direction texture |
There are two types which do the honors. Type 321 will operate to 2000 F (1093 C) and type 309 to 2240 F (1227 C); type 309 is more expensive and small addition of titanium in type 321 foil is said to absorb residual oxygen.
For part protection wrapping deals with two very common misconceptions. Scale is black iron oxide. Decarburization is a carbon deficient layer just below the scale which does not hardenable and cannot be visually detected without a proper etching technique. When you need part protection and there isn’t the opportunity for a vacuum atmosphere or atmosphere-treated part, Foil wrapping is the affordable solution to part protection.
Got the drawing and the application but no material call yet? Send the drawing for a feasibility check.
Certifications, Testing and Traceability
When looking to procure metals from Asia, buyers can find audits with advice as succinct as, “Mill Test Certifications are commonly forged, be very careful about an ISO 9001 certificate verify it with the issuer of the certification,” or, as our own firm likes to say: “Better to publish a guide of how to audit us than ask you to take our word.”
Why heat lots matter
A 2.2 test certificate could truthfully and will give you no idea of the coil in front of your eyes, since it was born in a different batch. 3.1 provides evidence for the heat batch that actually was delivered, witnessed by a quality function not reporting to production.
Where purchase orders just state “MTC required”, EN 10204 3.1 type is what the mill will offer as. The material manufactured to the American Standard and produced by Asian mills is generally specified as EN 10204 3.1 / 3.2 against buyer’s specific agreement.
The costliest error is regarding a certificate as proof, rather than as a testable assertion. Falsifying it is inexpensive to create and costly to find at the works, and risk doesn’t vanish simply because a supplier is big – audit guidelines warn that capacity-pressured mills sublet to unregistered workshops. At least four tests are worth having on a thin-gauge stainless supplier – including our own:
- Make absolutely sure you check the ISO certificate number yourself by asking the certification body, not the supplier.
- Select a completed coil and request a traceable run back to its originating heat number.
- Carry out a positive material identification using the X-ray fluorescence gun upon receipt of the material, verify carbon-grade markings and for L and Mo-bearing grades look at molybdenum content.
- Check the grade on the paperwork matches the type given in the purchase order
Would you like the bundle first before making a first commitment?
Ask for the certificate and test report set →Sourcing Stainless Steel Foil — What an RFQ Must Specify
The common denominator in delayed first-order queries are; grade, thickness, quantity. Those three allow a mill to guess the other four which drive the price and lead-time. We supply stainless steel foil to a specification written on a purchase order, and, to be able to offer a quick quote, we need the 8 data-fields below;
- Material Grade & Specification; example; 316L to ASTM A240/A240M or; EN 1.4404 to EN10088-2.
- Nominal thickness & tolerance frame; example; 0.10mm, T to EN 10024.
- Finished Width & Type of Slit; example; 200mm slit edge.
- Temper; example; annealed, Q temp, H, S temp, SS temp.
- Surface finish; examples; BA or 2B, with a roughness limit if subsequent operations like plating or bonding require it.
- Downstream processes; example; stamping, laser cutting, winding.
- Certificate; type; example; EN 10204-2.1, EN 10204-3.1, EN 10204-3.2, PMI or; other type.
- Form & packaging; example; in-coil or cut sheet, coil weight and bore diameter, interlayer material and wrapping and whether it will be shipped either eye-up or eye-horizontal.
One line that removes a whole round of emails
The specification should be a single written string: Grade – Thickness – Tolerance Frame – Finished Width – Temper – Surface Finish – Certificate. Example of a specification to support this: ‘316L – 0.10mm – EN ISO 9445 – 200mm slit -annealed – 2B – EN10204-3.1’. Requests of, for instance, “SS foil, cheap, quantity 500kg’ will take 3 more stages to arrive.
What actually moves the price
The price of foil is determined not solely on price/kg, but on a combination of price drivers, which you then have an opportunity to influence. Quotation drivers for cold-rolled stainless foil. Figures are established at enquiry against your specification.
| Driver | Effect on the quotation |
|---|---|
| Alloy content | Nickel and molybdenum bearing grades carry a raw-material premium over 200-series and ferritic grades |
| Thickness band | Each band down adds rolling passes, intermediate annealing and yield loss |
| Width and slitting | Narrow widths multiply slitting operations and scrap per finished meter |
| Temper | Spring and full hard require controlled final reduction; annealed requires a furnace pass |
| Surface finish | Bright annealing needs protective atmosphere capacity; 2B and 2D route through pickling |
| Tolerance class | Tightening below the standard table shifts the accept-reject line and the yield |
| Certification level | 3.2 adds third-party witnessing time; additional PMI or mechanical testing adds lab time |
| Packing specification | Export packing, moisture barrier and pallet type are quoted per shipping mode |
Packing is a technical requirement at foil gauge
Failure in transport resulting in cracked edges and collapsed cores is now why so many international thin-coil orders end when delivered into the buyer’s receiving departments. Paper interleaving, with appropriate moisture barrier wraps, is essential to ensure coils arrive undamaged with strapping, with internal paper, plastic slip sheets, or fully boxed coils to the receiving company’s specification; the correct shipping orientation being listed on the specification form and the pallet labelled with product identity & heat number.
Choosing based on the lowest headline number of the purchase specification price often does not result in the most economical solution in respect of price per kg from goods inwards onwards. A quoted price that does not specify the edge condition or certificate may appear cheaper, and then become prohibitively expensive once delivered; here our L1099 TIF Cert, with in house precise slitting is factored into line price and not added separately at the end.
After that initial set of eight fields have been established the lead time and MOQ is determined through the grade, then the thickness band then width. After a specification is agreed (reviewed by our technical enquiry desk) we return a written quote with those details, and the wider stainless steel product range covers the same grades in coil, plate, pipe and bar.
Stainless Steel Foil Engineering Tools
Foil Gauge Converter
Accurately convert stainless steel foil thickness between gauges, millimeters, and inches for precise specification.
Foil RFQ Builder
Configure your stainless steel foil requirements and generate a standardized Request for Quote instantly.
Foil Grade Selector
Compare mechanical properties and chemical compositions to select the optimal stainless steel foil grade.
Foil Coil Calculator
Calculate foil coil weight, length, and outside diameter to optimize your shipping and production planning.
Stainless Steel Foil FAQ — Samples, MOQ, Certificates and Delivery
Yes. State the gauge ranges you want to use and a swatch set comes to us – all we need to get material for you to cut, formed or wrapped in so that you don’t have to over invest in the initial order.

