Stainless vs cast iron vs carbon steel: coating-free cookware compared

The short answer

Bare stainless, bare cast iron, and carbon steel are coating-free cook surfaces — no PTFE or ceramic film to wear off.[1][2] Acidic foods can pull nickel and chromium from stainless (highest when pans are new) and can pull dietary iron from cast iron; both effects depend on time, acidity, and prior use.[3][4] Carbon steel behaves like a lighter cast-iron cousin: oil seasoning, rust vigilance, excellent sear. On our methodology, bare stainless and carbon steel score 10/10 materials; bare cast iron 9.5; enameled iron 8.5.

As an Amazon Associate I earn from qualifying purchases. Affiliate status never changes rank. 0 paid placements. This is not medical advice — especially for nickel allergy or iron-restricted diets.

What “coating-free” means on this site

Consumer Reports notes that uncoated pans — including carbon steel and cast iron — are unlikely to contain PFAS, and that seasoned iron can become slick without a synthetic nonstick film.[1] Ecology Center’s FTIR work was aimed at identifying PTFE vs silicon-dioxide ceramic coatings on nonstick pans, not at declaring bare metal “toxics-free” in every sense.[2]

Our rankings therefore treat coating-free metals as the top materials band for a plastic-free / low-fluoropolymer preference, while still citing metal-release literature and XRF where enamel pigments enter the picture. Hybrid PTFE pans such as HexClad’s hybrid sit much lower because fluoropolymer valleys remain part of the cook surface — see our HexClad PTFE explainer.

Stainless steel: nickel, chromium, and acidic foods

Food-grade stainless is mostly iron with chromium (and often nickel) that form a passive oxide layer. It does not need oil seasoning the way bare iron does, and it shrugs off dishwashers and tomato simmering better than seasoned iron. The tradeoff is technique: stainless wants heat control and fat to reduce sticking; it is not a factory-slick nonstick pan.

Kamerud, Hobbie, and Anderson (Oregon State; Journal of Agricultural and Food Chemistry, 2013) cooked commercial tomato sauces with stainless grades and a saucepan. After six hours, nickel and chromium in sauce rose up to 26-fold and 7-fold versus sauce cooked without stainless, depending on grade; new stainless leached the most; leaching fell across repeated cycles and stabilized after about the sixth cycle, though contributions remained measurable — about 88 µg Ni and 86 µg Cr per 126 g serving by the tenth cycle in their average reported scenario.[3]

Those figures are experimental cooking results, not a claim that everyday 20-minute sauté matches a six-hour simmer. They do support a practical rule: if you are highly nickel-sensitive, long acidic cooks in brand-new stainless deserve more caution than a well-used skillet doing quick weeknight work. For shoppers prioritizing PTFE avoidance with published PFAS panels on stainless samples, our top seed entry is the Made In Stainless Clad Frying Pan (Light Labs cookware PFAS reports cited on that product page).[5][6]

Bare cast iron: seasoning, iron contribution, weight

Bare cast iron is high-carbon iron with a rough surface that builds a polymerized oil seasoning. Virginia Tech food scientist Sean O’Keefe describes seasoning as oil molecules combining under heat into a protective layer that limits rust and adds release — and notes bare cast iron will rust rapidly without that layer because it lacks stainless’s chromium oxide film.[7]

Brittin and Nossaman (Journal of the American Dietetic Association, 1986) cooked twenty foods in iron vs non-iron utensils: 90% of foods contained significantly more iron when cooked in iron, with acidity, moisture, and cooking time significant factors.[4] A later systematic review of iron cookware/ingots similarly reports that cooking in iron can raise food iron content, with study quality and clinical anemia outcomes mixed enough that authors call for more research.[8]

O’Keefe’s practical caveat matches home-cook experience: a well-seasoned pan can handle short acidic contact, but long tomato simmering is a better job for enamel or stainless.[7] Cast iron is heavy, holds heat, and goes stove-to-oven; it is a poor pick if you want a light pan for constant tossing.

We do not yet seed a bare cast-iron skillet SKU; enameled iron is represented by Staub and Le Creuset — PTFE-free enamel over iron, with XRF pigment caveats covered in our enamel lead/XRF journal.

Carbon steel: lighter iron, same seasoning logic

Carbon steel is mostly iron with less carbon than cast iron, rolled thinner. Consumer Reports groups carbon steel with cast iron as uncoated options unlikely to contain PFAS, noting that seasoning can become “like a nonstick coating” over time.[1] Care rules rhyme with cast iron: dry thoroughly, oil lightly, avoid dishwasher neglect, and treat long acidic braises as seasoning-stripping events.

Compared with cast iron, carbon steel usually heats and cools faster and weighs less — better for sauté motion and restaurant-style tossing — while offering less thermal mass for deep frying or cornbread. Our materials scores give carbon steel the same 10/10 materials band as bare stainless because both avoid fluoropolymer and ceramic films; we still expect seasoning maintenance that stainless does not need.

No carbon-steel SKU is in the current seed ranking. If you send a brand COA, independent FTIR/XRF, or Light Labs-style panel for a specific carbon-steel pan, we will review it via Contact rather than inventing lab rows.

Side-by-side comparison

Use this table as a shopping compass, not a medical chart. Metal-release numbers below are from the cited studies’ conditions — we do not extrapolate them into homemade ppm claims for every brand.

Who each material suits

• Choose bare stainless if you want low-maintenance PTFE-free cooking, fond for pan sauces, and published PFAS screening on a clad line — start with Made In’s stainless clad pan and our full rankings.
• Choose bare cast iron if you value heat retention, oven work, and do not mind weight plus seasoning rituals — and move long tomato braises to enamel or stainless.[7]
• Choose carbon steel if you want cast-iron behavior in a lighter skillet and will maintain seasoning; treat it as a skill pan, not a wipe-clean nonstick substitute.[1]
• Choose enameled cast iron if you want iron’s oven performance without bare-iron seasoning, accepting enamel pigment homework — see Staub/Le Creuset entries and the XRF enamel guide.
• Skip “non-toxic” marketing on hybrid PTFE pans when your goal is coating-free metal; read HexClad hybrid PTFE explained first.

How this maps to our scoring (without inventing products)

Materials scores are fixed by cook-surface class in code and documented on /methodology: bare_stainless 10, carbon_steel 10, bare_cast_iron 9.5, enameled_cast_iron 8.5, ceramic_nonstick 5.5, hybrid_ptfe 3.5, traditional_ptfe 2.[11] Lab evidence is a separate axis — Made In’s Light Labs panels can lift stainless evidence scores; bare iron without a cited independent test stays at “no published lab data” until a source exists.[5][6] Consumer Reports’ safer-kitchenware guidance likewise steers PFAS-avoiding shoppers toward uncoated stainless and cast iron rather than PTFE nonstick.[10]

Ceramic nonstick is still a coating, not a peer of these three metals — details in Is ceramic nonstick actually non-toxic?.

FAQ

Which is the most “non-toxic” of the three?

None is a blank toxics certificate. All three avoid PTFE/ceramic films.[1][2] Stainless raises nickel/chromium questions with long acidic cooks; iron raises dietary iron transfer questions.[3][4] Pick based on your constraints (nickel sensitivity, iron intake, maintenance tolerance), not a single marketing adjective.

Is seasoned cast iron basically Teflon?

No. Seasoning is polymerized cooking oil on iron, not a fluoropolymer coating.[7] It can flake or strip with abuse and can be rebuilt; PTFE-family films are a different chemistry class authorized for food contact under 21 CFR 177.1550 when they meet that rule’s limits.[9]

Can I simmer tomato sauce in stainless every week?

Many households do. The Kamerud study shows measurable Ni/Cr transfer that is highest on new pans and long cooks.[3] If you have clinician guidance on nickel, follow that; otherwise stainless remains our default PTFE-free sauce pan on the rankings.

Why rank enameled iron if this post is about bare metals?

Because shoppers often cross-shop Dutch ovens when they leave nonstick. Enamel removes seasoning chores but adds glaze/pigment variables — scored separately at 8.5 materials and discussed in our enamel XRF post.

Do you sell or endorse a carbon-steel brand yet?

Not in the seed dataset. The materials class exists in scoring so we can add a SKU when evidence and product notes are ready — send sources via Contact.

References

1. Consumer Reports — You Can’t Always Trust Claims on ‘Non-Toxic’ Cookware (https://www.consumerreports.org/toxic-chemicals-substances/you-cant-always-trust-claims-on-non-toxic-cookware-a4849321487/)
2. Ecology Center — What’s Cooking? (https://www.ecocenter.org/our-work/healthy-stuff-lab/reports/whats-cooking)
3. Kamerud et al. — Stainless steel leaches nickel and chromium into foods during cooking (PubMed 23984718) (https://pubmed.ncbi.nlm.nih.gov/23984718/)
4. Brittin & Nossaman — Iron content of food cooked in iron utensils (PubMed 3722654) (https://pubmed.ncbi.nlm.nih.gov/3722654/)
5. Light Labs — Made In Cookware PFAS report (https://app.lightlabs.com/comprehensive-testing-report/69/1621)
6. Light Labs — Made In Cookware PFAS report (later panel) (https://app.lightlabs.com/comprehensive-testing-report/69/244)
7. Virginia Tech News — Cast iron myths (O’Keefe) (https://news.vt.edu/content/news_vt_edu/en/articles/2024/08/cast-iron-myths.html)
8. Sharma & Priti — Effect of cooking food in iron-containing cookware… systematic review (PubMed 34290890) (https://pubmed.ncbi.nlm.nih.gov/34290890/)
9. eCFR — 21 CFR 177.1550 Perfluorocarbon resins (https://www.ecfr.gov/current/title-21/chapter-I/subchapter-B/part-177/subpart-B/section-177.1550)
10. Consumer Reports — Opt for safer kitchenware (https://www.consumerreports.org/home-garden/opt-for-safer-kitchenware-a2506781798/)
11. Best Cookware Ranked — methodology materials scores (https://best-cookware-ranked.com/methodology)