Corrosion Resistance Finder

Find alloys that resist specific corrosive environments — saltwater, acids, high temperature oxidation, and more.

Finder

How to Use

  1. 1
    Select the Alloy and Corrosive Medium

    Choose the alloy grade from the database and specify the corrosive environment — such as dilute sulfuric acid, seawater, sodium chloride solution, or humid atmosphere — along with concentration and temperature.

  2. 2
    Review the Corrosion Resistance Rating

    Read the resistance rating (Excellent / Good / Fair / Poor / Not Recommended) for the selected alloy-medium combination, with typical corrosion rate ranges where available.

  3. 3
    Explore Alternative Alloys

    If the selected alloy is rated Fair or Poor, browse the suggested alternatives sorted by resistance rating to identify a more suitable material for your specific environment.

About

Corrosion is the most costly form of materials degradation, with global annual costs estimated in the trillions of dollars. Selecting an alloy with adequate corrosion resistance for its service environment is therefore one of the highest-return investments an engineer can make in the design phase. The complexity lies in the enormous number of alloy-environment combinations: a grade that performs excellently in nitric acid may fail rapidly in hydrochloric acid at the same concentration.

The AlloyFYI Corrosion Resistance Finder consolidates data from NACE International publications, ISO 8044 corrosion terminology standards, and alloy supplier corrosion handbooks into a searchable database organized by alloy family and corrosive medium category. The tool covers aqueous corrosion (acids, alkalis, salt solutions, natural waters), atmospheric corrosion (rural, urban, marine, industrial), high-temperature oxidation and sulfidation, and galvanic compatibility. Each rating is linked to source data and notes on limiting conditions such as maximum safe temperature or concentration.

FAQ

What is the difference between general corrosion and pitting corrosion?
General (uniform) corrosion consumes metal at a roughly equal rate across the entire exposed surface, making it predictable and manageable through thickness allowances in design. Pitting corrosion is localized attack that creates small, deep cavities, often in alloys that rely on passive oxide films such as stainless steels and aluminum. Pitting is particularly insidious because wall penetration can occur even when average metal loss is negligible. Chloride ions are the primary trigger, destabilizing the passive film and initiating pits. Materials with high PREN values resist pitting more effectively.
How does galvanic corrosion occur and how can it be prevented?
Galvanic corrosion occurs when two dissimilar metals in electrical contact are immersed in an electrolyte; the less noble metal (anode) corrodes preferentially at an accelerated rate. The driving force is the potential difference in the galvanic series. Prevention strategies include selecting alloys close together in the galvanic series, insulating dissimilar metal contacts with non-conductive gaskets or coatings, ensuring the anode-to-cathode area ratio is as large as possible (a small anode corrodes rapidly), applying protective coatings to the cathode, or using cathodic protection.
Why does stainless steel corrode in some environments?
Stainless steel's corrosion resistance depends on a thin (approximately 2–3 nm) passive chromium oxide film on the surface. This film is stable in many environments but breaks down in high chloride concentrations (seawater, de-icing salts), reducing acids (hydrochloric acid), and under crevices or deposits where oxygen depletion prevents film repassivation. Selecting a higher-alloyed grade (duplex 2205, super-duplex 2507, or 6Mo austenitic alloys) with increased chromium, molybdenum, and nitrogen content provides substantially better resistance to these breakdown mechanisms.
What does 'isocorrosion' mean in corrosion charts?
Isocorrosion charts plot corrosion rate contours (typically 0.1 mm/year and 1.0 mm/year) on axes of temperature versus acid concentration for a specific alloy-medium combination. The 0.1 mm/year isocorrosion line is commonly used as the boundary for acceptable service (the 'practical immunity' region below it), while the 1.0 mm/year line defines the limit for applications where higher corrosion rates can be tolerated with appropriate thickness allowances. These charts allow engineers to verify that service conditions fall safely below the critical threshold for the selected alloy.
How does surface finish affect corrosion resistance?
Surface finish significantly influences corrosion behavior. Rough surfaces trap electrolyte, debris, and biological fouling, creating crevice conditions that locally deplete oxygen and promote crevice corrosion. A finer surface finish (lower Ra) reduces these sites and also improves the quality and uniformity of passive oxide films on stainless steels and aluminum alloys. Electropolishing of stainless steel removes inclusions and surface damage from machining, producing a chromium-enriched surface layer with measurably superior pitting resistance compared to mechanically polished surfaces of the same alloy.
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