{
  "spore": "profile",
  "id": "chromium-oxide-coating",
  "spore_version": "0.2",
  "family": "oxide-ceramics",
  "name": "Chromium oxide thermal spray coating (Cr2O3, chromia)",
  "abbreviation": "Cr2O3",
  "role": "Hard ceramic wear and seal-face coating, sprayed onto steel parts",
  "category": "coatings",
  "type": "anodize",
  "summary": "Chromium(III) oxide (chromia, Cr2O3) is sprayed onto steel by atmospheric plasma spraying to form a hard ceramic layer. Vickers microhardness of the plasma-sprayed Metco 6156 coating was 1496 HV300 g in one test and 1762 HV300 g in another, per Odhiambo et al. The coating is brittle, so it chips under point impact and its thickness is limited before it spalls, according to the HTS Coatings technical data table.\n",
  "best_for": "Wear-resistant, sliding and abrasive contact faces on steel, such as printing anilox rolls and mechanical seal faces, where the part does not take impact",
  "weakest_at": "Brittleness: chromia chips under point-loaded impact or edge loading, and thick build-up risks spalling (HTS Coatings)",
  "identity": {
    "formula": "Cr2O3",
    "cas": "1308-38-9",
    "crystal_system": "trigonal (corundum structure)",
    "space_group": "R-3c (No. 167)",
    "designations": [
      {
        "system": "Trade name",
        "code": "Metco 6156",
        "source": "odhiambo2021",
        "where": "Experimental details, first paragraph: commercially available powder (Metco 6156)"
      }
    ],
    "source": "wikipedia-cr2o3",
    "where": "Chembox: CAS number, crystal structure (corundum) and space group sections"
  },
  "tags": {
    "environments": [],
    "stresses": [],
    "applications": []
  },
  "properties": [
    {
      "benchmark": "density",
      "label": "Density of crystalline chromium(III) oxide",
      "value": 5.22,
      "bound": "exact",
      "unit": "g/cm3",
      "scope": "material",
      "conditions": {
        "basis": "bulk crystalline Cr2O3 at 25 degC as printed in the Merck Index entry",
        "not_a": "sprayed coating density"
      },
      "method": "Value printed in the experimental-properties section of the PubChem record, citing the Merck Index",
      "status": "ground",
      "source": "pubchem-cr2o3",
      "where": "Chemical and Physical Properties > Experimental Properties > Density, first entry (5.22 g/cm3 at 25 degC)",
      "source_detail": {
        "title": "PubChem compound record, Chromium(III) oxide (CID 517277): GHS classification and experimental properties",
        "id": "CID 517277; CAS 1308-38-9",
        "url": "https://pubchem.ncbi.nlm.nih.gov/rest/pug_view/data/compound/517277/JSON",
        "year": 2026,
        "kind": "database",
        "license": "public domain (NCBI)"
      }
    },
    {
      "benchmark": "melting_point",
      "label": "Melting point of chromium(III) oxide",
      "value": 2435,
      "bound": "exact",
      "unit": "°C",
      "scope": "material",
      "conditions": {
        "basis": "bulk crystalline Cr2O3 as printed in the Merck Index entry"
      },
      "method": "Value printed in the Chembox properties of the Wikipedia article (melting point 2435 °C, printed as 2,435 °C); the PubChem record prints the same figure from the Merck Index",
      "status": "ground",
      "source": "wikipedia-cr2o3",
      "where": "Chembox Properties, melting point: 2,435 °C (2435 °C in the infobox source)",
      "source_detail": {
        "title": "Chromium(III) oxide, Wikipedia",
        "id": "Wikipedia article Chromium(III) oxide",
        "url": "https://en.wikipedia.org/wiki/Chromium(III)_oxide",
        "year": 2026,
        "kind": "web",
        "license": "CC BY-SA 4.0 (Wikipedia)"
      }
    },
    {
      "benchmark": "vickers_hardness",
      "label": "Typical hardness of atmospheric plasma sprayed chromia",
      "value": 900,
      "value_high": 1200,
      "bound": "range",
      "unit": "HV300",
      "scope": "material",
      "conditions": {
        "form": "atmospheric plasma sprayed coating (typical APS)",
        "basis": "range printed for typical APS coatings in the technical data table"
      },
      "method": "Range printed in the HTS Coatings technical data table, Hardness (Vickers) row",
      "status": "ground",
      "source": "hts-chrome-oxide",
      "where": "Technical data table, Hardness (Vickers) row: 900-1200 HV300 typical APS",
      "source_detail": {
        "title": "Chrome oxide thermal spray coating: technical data table, applications and sources (HTS Coatings)",
        "id": "HTS Coatings product page, /coatings/chrome-oxide",
        "url": "https://htscoatings.com/coatings/chrome-oxide",
        "year": 2026,
        "kind": "web",
        "license": "supplier web page, linked not reproduced"
      }
    },
    {
      "benchmark": "rockwell_c_hardness",
      "label": "Hardness of chromia coating in Rockwell C",
      "value": 62,
      "value_high": 72,
      "bound": "range",
      "unit": "HRC",
      "scope": "material",
      "conditions": {
        "form": "chromia coating, range depends on formulation as printed"
      },
      "method": "Range printed in the HTS Coatings technical data table, Hardness (HRC) row",
      "status": "ground",
      "source": "hts-chrome-oxide",
      "where": "Technical data table, Hardness (HRC) row: 62-72 HRC depending on formulation",
      "source_detail": {
        "title": "Chrome oxide thermal spray coating: technical data table, applications and sources (HTS Coatings)",
        "id": "HTS Coatings product page, /coatings/chrome-oxide",
        "url": "https://htscoatings.com/coatings/chrome-oxide",
        "year": 2026,
        "kind": "web",
        "license": "supplier web page, linked not reproduced"
      }
    },
    {
      "benchmark": "vickers_hardness",
      "label": "Microhardness of plasma sprayed Metco 6156, first coating",
      "value": 1496,
      "bound": "exact",
      "unit": "HV300 g",
      "scope": "material",
      "conditions": {
        "feedstock": "Metco 6156 chromium oxide powder",
        "process": "atmospheric plasma spray, no bond coat, 550 A arc current",
        "load": "300 g",
        "dwell": "15 s"
      },
      "method": "Mean Vickers microhardness on polished cross-sections, as stated in the microhardness section",
      "status": "ground",
      "note": "The conclusion section of the same paper prints 1497 HV for this coating, one unit higher.",
      "source": "odhiambo2021",
      "where": "Microhardness section (Vickers microhardness values for 550A)",
      "source_detail": {
        "title": "Influence of plasma spraying current on the microstructural characteristics and tribological behaviour of plasma sprayed Cr2O3 coating",
        "id": "doi:10.1016/j.bsecv.2020.03.007 (Bol. Soc. Esp. Ceram. Vidr. 60, 338-346, 2021)",
        "url": "https://www.elsevier.es/en-revista-boletin-sociedad-espanola-ceramica-vidrio-26-articulo-influence-plasma-spraying-current-on-S0366317520300340",
        "year": 2021,
        "kind": "paper",
        "license": "open access, as listed on the journal page"
      }
    },
    {
      "benchmark": "vickers_hardness",
      "label": "Microhardness of plasma sprayed Metco 6156, second coating",
      "value": 1762,
      "bound": "exact",
      "unit": "HV300 g",
      "scope": "material",
      "conditions": {
        "feedstock": "Metco 6156 chromium oxide powder",
        "process": "atmospheric plasma spray, no bond coat, 650 A arc current",
        "load": "300 g",
        "dwell": "15 s"
      },
      "method": "Mean Vickers microhardness on polished cross-sections, as stated in the microhardness section",
      "status": "ground",
      "note": "The conclusion section of the same paper prints 1763 HV for this coating, one unit higher.",
      "source": "odhiambo2021",
      "where": "Microhardness section (Vickers microhardness values for 650A)",
      "source_detail": {
        "title": "Influence of plasma spraying current on the microstructural characteristics and tribological behaviour of plasma sprayed Cr2O3 coating",
        "id": "doi:10.1016/j.bsecv.2020.03.007 (Bol. Soc. Esp. Ceram. Vidr. 60, 338-346, 2021)",
        "url": "https://www.elsevier.es/en-revista-boletin-sociedad-espanola-ceramica-vidrio-26-articulo-influence-plasma-spraying-current-on-S0366317520300340",
        "year": 2021,
        "kind": "paper",
        "license": "open access, as listed on the journal page"
      }
    },
    {
      "benchmark": "bond_strength",
      "label": "Bond strength of atmospheric plasma sprayed chromia on steel",
      "value": 4000,
      "value_high": 6000,
      "bound": "range",
      "unit": "psi",
      "scope": "material",
      "conditions": {
        "form": "atmospheric plasma spray on steel",
        "basis": "range printed in the technical data table"
      },
      "method": "Range printed in the HTS Coatings technical data table, Bond strength row",
      "status": "ground",
      "source": "hts-chrome-oxide",
      "where": "Technical data table, Bond strength row: 4,000-6,000 psi on steel (APS)",
      "source_detail": {
        "title": "Chrome oxide thermal spray coating: technical data table, applications and sources (HTS Coatings)",
        "id": "HTS Coatings product page, /coatings/chrome-oxide",
        "url": "https://htscoatings.com/coatings/chrome-oxide",
        "year": 2026,
        "kind": "web",
        "license": "supplier web page, linked not reproduced"
      }
    },
    {
      "benchmark": "bond_strength",
      "label": "Tensile bond strength, first coating (550A)",
      "value": 12.24,
      "bound": "exact",
      "unit": "MPa",
      "scope": "material",
      "conditions": {
        "feedstock": "Metco 6156",
        "process": "atmospheric plasma spray, no bond coat, 550 A",
        "thickness": "348 um as printed",
        "failure": "adhesive"
      },
      "method": "Tensile adhesion test in the paper, which says it followed the ASTM C633 procedure",
      "status": "ground",
      "source": "odhiambo2021",
      "where": "Table 4, averaged tensile bond strength results (550A, 12.24 MPa, adhesive failure)",
      "source_detail": {
        "title": "Influence of plasma spraying current on the microstructural characteristics and tribological behaviour of plasma sprayed Cr2O3 coating",
        "id": "doi:10.1016/j.bsecv.2020.03.007 (Bol. Soc. Esp. Ceram. Vidr. 60, 338-346, 2021)",
        "url": "https://www.elsevier.es/en-revista-boletin-sociedad-espanola-ceramica-vidrio-26-articulo-influence-plasma-spraying-current-on-S0366317520300340",
        "year": 2021,
        "kind": "paper",
        "license": "open access, as listed on the journal page"
      }
    },
    {
      "benchmark": "bond_strength",
      "label": "Tensile bond strength, second coating (650A)",
      "value": 23.6,
      "bound": "exact",
      "unit": "MPa",
      "scope": "material",
      "conditions": {
        "feedstock": "Metco 6156",
        "process": "atmospheric plasma spray, no bond coat, 650 A",
        "thickness": "391 um as printed",
        "failure": "adhesive"
      },
      "method": "Tensile adhesion test in the paper, which says it followed the ASTM C633 procedure",
      "status": "ground",
      "source": "odhiambo2021",
      "where": "Table 4, averaged tensile bond strength results (650A, 23.60 MPa, adhesive failure)",
      "source_detail": {
        "title": "Influence of plasma spraying current on the microstructural characteristics and tribological behaviour of plasma sprayed Cr2O3 coating",
        "id": "doi:10.1016/j.bsecv.2020.03.007 (Bol. Soc. Esp. Ceram. Vidr. 60, 338-346, 2021)",
        "url": "https://www.elsevier.es/en-revista-boletin-sociedad-espanola-ceramica-vidrio-26-articulo-influence-plasma-spraying-current-on-S0366317520300340",
        "year": 2021,
        "kind": "paper",
        "license": "open access, as listed on the journal page"
      }
    },
    {
      "benchmark": "bond_strength",
      "label": "Bond strength of Rokide C combustion-sprayed rod coating",
      "value": 4545,
      "bound": "exact",
      "unit": "psi",
      "scope": "material",
      "conditions": {
        "product": "Rokide C chrome oxide ceramic rod (mostly Cr2O3 with silica and alumina), combustion rod spray",
        "form": "combustion-sprayed rod coating"
      },
      "method": "Value printed in the Rokide C technical bulletin, Mechanical section",
      "status": "ground",
      "source": "rokide-c-tds",
      "where": "Coating features, Mechanical: Bond Strength 4545 psi",
      "source_detail": {
        "title": "Rokide C (Chrome Oxide) ceramic rod for thermal spraying, Saint-Gobain Coating Solutions technical bulletin",
        "id": "Saint-Gobain Coating Solutions Rokide C bulletin, copy on Alloy Coating Supply",
        "url": "https://store.alloycoatingsupply.com/wp-content/uploads/2023/11/Rokide-C-Rods-Technical-Data-Sheet.pdf",
        "year": 2023,
        "kind": "datasheet",
        "license": "manufacturer document, linked not reproduced"
      }
    },
    {
      "benchmark": "porosity",
      "label": "Porosity of plasma sprayed Metco 6156, first coating (550A)",
      "value": 8,
      "bound": "exact",
      "unit": "%",
      "scope": "material",
      "conditions": {
        "feedstock": "Metco 6156",
        "process": "atmospheric plasma spray, 550 A"
      },
      "method": "Porosity by image analysis of SEM micrographs, as stated in the paper",
      "status": "ground",
      "note": "The results section text is garbled for this value; the correlation section prints 8% in full.",
      "source": "odhiambo2021",
      "where": "Correlation of the results and the discussion: porosities 8% and 4% for 550A and 650A",
      "source_detail": {
        "title": "Influence of plasma spraying current on the microstructural characteristics and tribological behaviour of plasma sprayed Cr2O3 coating",
        "id": "doi:10.1016/j.bsecv.2020.03.007 (Bol. Soc. Esp. Ceram. Vidr. 60, 338-346, 2021)",
        "url": "https://www.elsevier.es/en-revista-boletin-sociedad-espanola-ceramica-vidrio-26-articulo-influence-plasma-spraying-current-on-S0366317520300340",
        "year": 2021,
        "kind": "paper",
        "license": "open access, as listed on the journal page"
      }
    },
    {
      "benchmark": "porosity",
      "label": "Porosity of plasma sprayed Metco 6156, second coating (650A)",
      "value": 4,
      "bound": "exact",
      "unit": "%",
      "scope": "material",
      "conditions": {
        "feedstock": "Metco 6156",
        "process": "atmospheric plasma spray, 650 A"
      },
      "method": "Porosity by image analysis of SEM micrographs, as stated in the paper",
      "status": "ground",
      "note": "The results section text is garbled for this value; the correlation section prints 4% in full.",
      "source": "odhiambo2021",
      "where": "Correlation of the results and the discussion: porosities 8% and 4% for 550A and 650A",
      "source_detail": {
        "title": "Influence of plasma spraying current on the microstructural characteristics and tribological behaviour of plasma sprayed Cr2O3 coating",
        "id": "doi:10.1016/j.bsecv.2020.03.007 (Bol. Soc. Esp. Ceram. Vidr. 60, 338-346, 2021)",
        "url": "https://www.elsevier.es/en-revista-boletin-sociedad-espanola-ceramica-vidrio-26-articulo-influence-plasma-spraying-current-on-S0366317520300340",
        "year": 2021,
        "kind": "paper",
        "license": "open access, as listed on the journal page"
      }
    },
    {
      "benchmark": "porosity",
      "label": "Porosity of standard atmospheric plasma sprayed chromia",
      "value": 5,
      "bound": "upper",
      "unit": "%",
      "scope": "material",
      "conditions": {
        "form": "standard APS coating, not the dense sintered-powder anilox grade"
      },
      "method": "Upper limit printed in the HTS Coatings technical data table",
      "status": "ground",
      "source": "hts-chrome-oxide",
      "where": "Technical data table, As-sprayed porosity row: up to 5% on standard APS",
      "source_detail": {
        "title": "Chrome oxide thermal spray coating: technical data table, applications and sources (HTS Coatings)",
        "id": "HTS Coatings product page, /coatings/chrome-oxide",
        "url": "https://htscoatings.com/coatings/chrome-oxide",
        "year": 2026,
        "kind": "web",
        "license": "supplier web page, linked not reproduced"
      }
    },
    {
      "benchmark": "porosity",
      "label": "Total porosity of Rokide C combustion-sprayed rod coating",
      "value": 8.4,
      "bound": "exact",
      "unit": "%",
      "scope": "material",
      "conditions": {
        "product": "Rokide C chrome oxide ceramic rod, combustion rod spray"
      },
      "method": "Value printed in the Rokide C technical bulletin, Physical section",
      "status": "ground",
      "source": "rokide-c-tds",
      "where": "Coating features, Physical: Total porosity 8.4%",
      "source_detail": {
        "title": "Rokide C (Chrome Oxide) ceramic rod for thermal spraying, Saint-Gobain Coating Solutions technical bulletin",
        "id": "Saint-Gobain Coating Solutions Rokide C bulletin, copy on Alloy Coating Supply",
        "url": "https://store.alloycoatingsupply.com/wp-content/uploads/2023/11/Rokide-C-Rods-Technical-Data-Sheet.pdf",
        "year": 2023,
        "kind": "datasheet",
        "license": "manufacturer document, linked not reproduced"
      }
    },
    {
      "benchmark": "max_service_temp",
      "label": "Maximum service temperature for wear service",
      "value": 540,
      "bound": "exact",
      "unit": "°C",
      "scope": "material",
      "conditions": {
        "service": "dry abrasive wear service"
      },
      "method": "Value printed in the HTS Coatings technical data table, metric row",
      "status": "ground",
      "source": "hts-chrome-oxide",
      "where": "Technical data table, Max service temp (metric row): 540 °C wear service",
      "source_detail": {
        "title": "Chrome oxide thermal spray coating: technical data table, applications and sources (HTS Coatings)",
        "id": "HTS Coatings product page, /coatings/chrome-oxide",
        "url": "https://htscoatings.com/coatings/chrome-oxide",
        "year": 2026,
        "kind": "web",
        "license": "supplier web page, linked not reproduced"
      }
    },
    {
      "benchmark": "max_service_temp",
      "label": "Maximum service temperature for sealed corrosive service",
      "value": 177,
      "value_high": 205,
      "bound": "range",
      "unit": "°C",
      "scope": "material",
      "conditions": {
        "service": "sealed coating in corrosive chemical environments"
      },
      "method": "Range printed in the HTS Coatings technical data table, metric row",
      "status": "ground",
      "source": "hts-chrome-oxide",
      "where": "Technical data table, Max service temp (metric row): 177-205 °C sealed corrosive service",
      "source_detail": {
        "title": "Chrome oxide thermal spray coating: technical data table, applications and sources (HTS Coatings)",
        "id": "HTS Coatings product page, /coatings/chrome-oxide",
        "url": "https://htscoatings.com/coatings/chrome-oxide",
        "year": 2026,
        "kind": "web",
        "license": "supplier web page, linked not reproduced"
      }
    },
    {
      "benchmark": "coating_thickness",
      "label": "Typical thickness of thermal sprayed chromia",
      "value": 75,
      "value_high": 640,
      "bound": "range",
      "unit": "µm",
      "scope": "material",
      "conditions": {
        "process": "typical thermal spray chromia coating"
      },
      "method": "Range printed in the HTS Coatings technical data table, Typical thickness row",
      "status": "ground",
      "source": "hts-chrome-oxide",
      "where": "Technical data table, Typical thickness row: 3-25 (75-640 µm)",
      "source_detail": {
        "title": "Chrome oxide thermal spray coating: technical data table, applications and sources (HTS Coatings)",
        "id": "HTS Coatings product page, /coatings/chrome-oxide",
        "url": "https://htscoatings.com/coatings/chrome-oxide",
        "year": 2026,
        "kind": "web",
        "license": "supplier web page, linked not reproduced"
      }
    },
    {
      "benchmark": "density",
      "label": "Bulk density of Rokide C ceramic rod",
      "value": 4.5,
      "bound": "exact",
      "unit": "g/cc",
      "scope": "material",
      "conditions": {
        "product": "Rokide C chrome oxide ceramic rod, mostly Cr2O3",
        "note": "a rod product figure, not the density of pure chromia"
      },
      "method": "Value printed in the Rokide C technical bulletin, Physical section",
      "status": "ground",
      "source": "rokide-c-tds",
      "where": "Coating features, Physical: Bulk Density 4.5 g/cc",
      "source_detail": {
        "title": "Rokide C (Chrome Oxide) ceramic rod for thermal spraying, Saint-Gobain Coating Solutions technical bulletin",
        "id": "Saint-Gobain Coating Solutions Rokide C bulletin, copy on Alloy Coating Supply",
        "url": "https://store.alloycoatingsupply.com/wp-content/uploads/2023/11/Rokide-C-Rods-Technical-Data-Sheet.pdf",
        "year": 2023,
        "kind": "datasheet",
        "license": "manufacturer document, linked not reproduced"
      }
    },
    {
      "benchmark": "particle_size",
      "label": "Feedstock particle size, Metco 6156 powder",
      "value": -35,
      "value_high": 15,
      "bound": "range",
      "unit": "µm",
      "scope": "material",
      "conditions": {
        "product": "Metco 6156 powder as received, sieve range as printed"
      },
      "method": "Size range printed in the Experimental details section of the paper",
      "status": "ground",
      "source": "odhiambo2021",
      "where": "Experimental details, first paragraph and Table 1: particle size -35 to +15 um",
      "source_detail": {
        "title": "Influence of plasma spraying current on the microstructural characteristics and tribological behaviour of plasma sprayed Cr2O3 coating",
        "id": "doi:10.1016/j.bsecv.2020.03.007 (Bol. Soc. Esp. Ceram. Vidr. 60, 338-346, 2021)",
        "url": "https://www.elsevier.es/en-revista-boletin-sociedad-espanola-ceramica-vidrio-26-articulo-influence-plasma-spraying-current-on-S0366317520300340",
        "year": 2021,
        "kind": "paper",
        "license": "open access, as listed on the journal page"
      }
    }
  ],
  "corrosion": [
    {
      "environment": "Sealed chromia in acidic and alkaline solutions",
      "headline": "The HTS page says sealed coatings hold up through 30-day immersion across pH 0-10 with no loss of wear resistance.",
      "effect": "The HTS page attributes this to a Journal of Thermal Spray Technology study of plasma sprayed chromia and alumina sealed with aluminum phosphates. The primary paper could not be opened for this profile, so the result rests on the HTS summary.",
      "rating": "low",
      "conditions": {
        "sealant": "aluminum phosphate (per the HTS page)",
        "test": "immersion in acidic and alkaline solutions, as summarized by HTS",
        "basis": "secondary summary of a primary study"
      },
      "source": "hts-chrome-oxide",
      "where": "Sources section (Journal of Thermal Spray Technology entry) and Where it doesn't section"
    },
    {
      "environment": "Unsealed plasma sprayed coating with open porosity",
      "headline": "Open porosity is the weak point: standard APS coatings run up to 5% porosity, so sealing is specified for aggressive chemistry.",
      "effect": "The HTS page lists sealing with epoxy, aluminum phosphate or polymer impregnation for aggressive chemical environments. The Odhiambo paper finds that the coating with higher porosity (8%) had the lower tensile bond strength (12.24 MPa against 23.60 MPa at 4%), so porosity also weakens the bond to the steel. This is an adhesion result, not a corrosion test.",
      "rating": "moderate",
      "conditions": {
        "basis": "qualitative corrosion ranking from the HTS page; porosity and bond comparison from the Odhiambo paper"
      },
      "source": "hts-chrome-oxide",
      "where": "Porosity bullet in Where it doesn't; Porosity row of the technical data table"
    },
    {
      "environment": "High temperature in wear or sealed corrosive service",
      "headline": "The table gives a wear ceiling of 540 °C and a sealed corrosive ceiling of 177 to 205 °C.",
      "effect": "The HTS page says the sealed corrosive ceiling is the limit in chemical service and advises stepping over to Cr3C2-NiCr for higher-temperature wear. The page does not say what fails above these ceilings.",
      "rating": "moderate",
      "conditions": {
        "basis": "service ceilings as printed by HTS Coatings"
      },
      "source": "hts-chrome-oxide",
      "where": "Technical data table, Max service temp row; Where it doesn't section"
    }
  ],
  "risks": {
    "hazards": [
      {
        "text": "PubChem's GHS summary for CID 517277 says the substance 'does not meet GHS hazard criteria for 57.8% (1112 of 1924) of all reports'. Its hazard statements are H302, H317, H319 and H360, with the signal word Danger and pictograms GHS07 and GHS08.",
        "ghs": [
          "H302",
          "H317",
          "H319",
          "H360"
        ],
        "source": "pubchem-cr2o3",
        "where": "Safety and Hazards, GHS Classification (CID 517277)"
      },
      {
        "text": "A Johnson Matthey safety data sheet for Katalco 71-5, a Grade 2 chromium(III) oxide classified by an EU registrant, is stricter. It lists H314 (causes severe skin burns and eye damage), H340, H350 (may cause cancer), H361 and H371, with the signal word Danger. It is a different product, but it shows that classifications for this oxide disagree between sources.",
        "ghs": [
          "H302",
          "H312",
          "H332",
          "H314",
          "H334",
          "H317",
          "H340",
          "H350",
          "H361",
          "H335",
          "H371",
          "H373",
          "H411"
        ],
        "source": "jm-katalco-sds",
        "where": "Section 1, classification and labelling: hazard statements and classification table"
      }
    ],
    "failure_risks": [
      {
        "mode": "Chipping under impact",
        "trigger": "Point-loaded impact or edge loading",
        "consequence": "Chromia is a ceramic, so impact chips the coating. The HTS page says to specify it for sliding, erosive and corrosive duty, not impact.",
        "severity": "moderate",
        "source": "hts-chrome-oxide",
        "where": "Limitations list, Brittle bullet"
      },
      {
        "mode": "Spalling of thick build-up",
        "trigger": "Build-up beyond the practical limit on cylindrical work",
        "consequence": "The HTS page says 'Thickness limited to roughly 25-30 mils on cylindrical work before residual stress risks spalling'. Typical thickness is 75 to 640 µm.",
        "severity": "moderate",
        "source": "hts-chrome-oxide",
        "where": "Limitations list, thickness bullet; Technical data table, Typical thickness row"
      },
      {
        "mode": "Service above the ceiling for the duty",
        "trigger": "Service above 540 °C for wear, or above 177 to 205 °C in sealed corrosive service",
        "consequence": "The table gives these as ceilings. The HTS page does not describe the failure mode above them.",
        "severity": "moderate",
        "source": "hts-chrome-oxide",
        "where": "Technical data table, Max service temp row"
      }
    ],
    "side_effects": [],
    "handling": [
      {
        "text": "For the Cr2O3-TiO2 blend Metco 6485 from the same maker (not pure chromia), keep the powder in its original container in a dry location, tumble it gently before use, and store open containers in a drying oven to prevent moisture pickup.",
        "source": "metco-6485-ds",
        "where": "Section 4.2, Handling Recommendations"
      },
      {
        "text": "The HTS page says finishing requires diamond wheels, so plan the cost and lead time.",
        "source": "hts-chrome-oxide",
        "where": "Introduction, closing caveats paragraph"
      }
    ],
    "mitigations": [
      {
        "text": "Seal the coating with epoxy, aluminum phosphate or polymer impregnation for aggressive chemical service.",
        "source": "hts-chrome-oxide",
        "where": "Porosity bullet in Where it doesn't"
      },
      {
        "text": "Apply over a corrosion-resistant bond coat for chemical service, as the HTS page describes for its own process.",
        "source": "hts-chrome-oxide",
        "where": "Introduction paragraph"
      }
    ]
  },
  "uses": [
    {
      "application": "mechanisms",
      "device": "Mechanical seal faces, pump sleeves and impellers",
      "example": "The HTS page lists mechanical seal faces, pump sleeves and impellers in abrasive slurry among the parts it coats with chromia.",
      "source": "hts-chrome-oxide",
      "where": "Introduction paragraph (We use it for ...) and Applications list"
    },
    {
      "application": "mechanisms",
      "device": "Flexographic printing anilox rolls, laser engraved after coating",
      "example": "The HTS page says chromia is the industry-standard surface for flexographic and gravure printing rolls because it takes laser engraving cleanly.",
      "source": "hts-chrome-oxide",
      "where": "Applications list and Where it earns its keep"
    },
    {
      "application": "mechanisms",
      "device": "Wire drawing capstans, draw blocks and sheaves",
      "example": "The Saint-Gobain Rokide C bulletin lists wire drawing capstans, wire draw blocks and sheaves among the parts for which the rod is used.",
      "source": "rokide-c-tds",
      "where": "Applications list (right column)"
    }
  ],
  "supply": [
    {
      "subject": "Chromium (chromite ore, the feedstock for chromia)",
      "producers": [
        {
          "country": "South Africa",
          "share_percent": 45.1,
          "year": 2025
        },
        {
          "country": "Turkey",
          "share_percent": 17.6,
          "year": 2025
        },
        {
          "country": "Kazakhstan",
          "share_percent": 13.7,
          "year": 2025
        },
        {
          "country": "India",
          "share_percent": 5.9,
          "year": 2025
        },
        {
          "country": "Brazil",
          "share_percent": 3.9,
          "year": 2025
        },
        {
          "country": "Zimbabwe",
          "share_percent": 3.9,
          "year": 2025
        },
        {
          "country": "Finland",
          "share_percent": 3.7,
          "year": 2025
        }
      ],
      "critical_lists": [],
      "recycling": "USGS: 'recycled chromium (contained in reported stainless-steel scrap receipts) accounted for 21% of apparent consumption' in the United States in 2025.",
      "substitutes": [],
      "source": "usgs-mcs2026-chromium",
      "where": "World Mine Production and Reserves table, 2025e column (world total printed as 51,000 thousand t; the table header gives chromium content); shares calculated by Space Mushroom from the seven countries listed; Recycling paragraph. Other countries (3,000 thousand t) are excluded from the shares."
    }
  ],
  "media": [],
  "documents": [
    {
      "title": "HTS Coatings: Chrome oxide technical data table (web product page)",
      "type": "datasheet",
      "url": "https://htscoatings.com/coatings/chrome-oxide",
      "year": 2026
    },
    {
      "title": "Saint-Gobain Rokide C (Chrome Oxide) ceramic rod technical bulletin, copy hosted by Alloy Coating Supply",
      "type": "datasheet",
      "url": "https://store.alloycoatingsupply.com/wp-content/uploads/2023/11/Rokide-C-Rods-Technical-Data-Sheet.pdf",
      "year": 2023
    },
    {
      "title": "Influence of plasma spraying current on the microstructural characteristics and tribological behaviour of plasma sprayed Cr2O3 coating (open access)",
      "type": "paper",
      "url": "https://www.elsevier.es/en-revista-boletin-sociedad-espanola-ceramica-vidrio-26-articulo-influence-plasma-spraying-current-on-S0366317520300340",
      "year": 2021
    },
    {
      "title": "USGS Mineral Commodity Summaries 2026: Chromium",
      "type": "report",
      "url": "https://pubs.usgs.gov/periodicals/mcs2026/mcs2026-chromium.pdf",
      "year": 2026
    },
    {
      "title": "PubChem: Chromium(III) oxide (CID 517277), GHS classification and experimental properties",
      "type": "database",
      "url": "https://pubchem.ncbi.nlm.nih.gov/rest/pug_view/data/compound/517277/JSON",
      "year": 2026
    },
    {
      "title": "Oerlikon Metco data sheet DSM-0387.1: Chromium Oxide - Titanium Oxide Powders (Metco 6485)",
      "type": "datasheet",
      "url": "https://www.oerlikon.com/ecoma/files/DSM-0387_Cr2O3_40TiO2.pdf?download=true",
      "year": 2024
    },
    {
      "title": "Johnson Matthey (C&L) safety data sheet, Cr - Chromium (III) Oxide, Katalco 71-5 (IUCLID 6 export)",
      "type": "sds",
      "url": "https://matthey.com/documents/161599/166998/Cr-Chromium-III-Oxide-Katalco-715.pdf/dcfbe5f7-6cc9-a7c9-0d92-7d2339ca4759",
      "year": 2020
    }
  ],
  "gaps": [
    "No vacuum, radiation, thermal-vacuum or flight data for chromia coatings were found in any source we hold; this profile has no space application.",
    "The Saint-Gobain chromia data sheet, the Saint-Gobain #300 series chromium oxide data sheet, the Cincinnati Thermal Spray CT1302-1 data sheet, the American Elements SDS and the Journal of Thermal Spray Technology paper by Leivo et al. on sealed chromia could not be opened (403, access denied or not found), so their figures are not used.",
    "The two MDPI papers on plasma sprayed Cr2O3 (Crystals 2023 and Coatings 2023) returned access denied, so their porosity, hardness and bond figures are not used.",
    "The Odhiambo paper states the feedstock as Blended in Table 1 but as sintered and crushed in its text, and gives 99.7 in Table 1 but 99% purity in its text; neither composition figure is recorded as a property.",
    "Odhiambo paper results section porosity values are garbled (8.% and 4.%); the correlation section values of 8% and 4% are used instead.",
    "Density of a sprayed pure chromia coating was not found; the 5.22 g/cm3 value is for bulk crystalline Cr2O3, and the 4.5 g/cc value is for the Rokide C rod, which is mostly Cr2O3.",
    "Coefficient of thermal expansion, thermal conductivity and total emittance for Rokide C are printed in exponent or estimate form and are left out (Rokide C bulletin, Thermal section).",
    "Atomic weights of chromium and oxygen and the crustal abundance of chromium were not read in any source we hold.",
    "Critical-mineral list status for chromium was not confirmed in the fetched USGS text, so no critical_lists entry is given.",
    "No UNS, EN, DIN, JIS or AISI designation was found for chromia powder or coating; only the Metco 6156 trade name is printed in a source.",
    "The sealed-chromia corrosion result rests on the HTS summary of the primary paper; no coating corrosion rate in mm per year or mass loss was found.",
    "Pure-chromia supplier SDS for hazards was not reachable; hazard data rest on PubChem and on one registrant classification for a different product (Katalco 71-5).",
    "Non-canonical benchmark names are used for hardness (vickers_hardness, rockwell_c_hardness), bond strength (bond_strength), porosity, coating thickness (coating_thickness) and particle size (particle_size)."
  ],
  "story": {
    "why": "Chromium(III) oxide, Cr2O3, is a corundum-structure oxide that is sprayed onto steel to make a hard, wear-resistant layer. The HTS Coatings technical table gives a typical Vickers hardness of 900 to 1200 HV300 for plasma sprayed coatings, and the Odhiambo paper measured 1496 HV300 g and 1762 HV300 g for two coatings sprayed at different currents. The trade-off is brittleness: the same sources say chromia chips under impact and must be sealed for chemical service. The HTS page points to sliding, abrasive and corrosive duty as where it is used.",
    "uses": [
      {
        "where": "Printing anilox rolls",
        "line": "The HTS page says chromia is the industry standard surface for flexographic and gravure printing rolls because it takes laser-engraved cells cleanly. It also lists mechanical seal faces and pump sleeves."
      },
      {
        "where": "Pump and seal parts",
        "line": "The Saint-Gobain Rokide C bulletin lists pump sleeves, pump shafts, impellers, mechanical seal faces and ball valves among the parts it coats. The rod is mostly Cr2O3 with silica and alumina, so it is not pure chromia."
      },
      {
        "where": "Wire drawing",
        "line": "Wire drawing capstans, draw blocks, sheaves and pulleys are also listed for the Rokide C rod. No space or flight use was found in any source we hold."
      }
    ],
    "can_do": [
      {
        "label": "Wear",
        "line": "Resist sliding and abrasive wear on steel parts. The HTS page calls chromia the hardest common oxide ceramic in thermal spray.",
        "scope": "material"
      },
      {
        "label": "Finish",
        "line": "Take a laser-engraved cell pattern for printing rolls, which is why it is used for anilox rolls.",
        "scope": "material"
      },
      {
        "label": "Chemistry",
        "line": "Hold up in alkaline or mildly acidic media when the coating is sealed, according to the HTS page.",
        "scope": "material"
      },
      {
        "label": "Seal faces",
        "line": "Work as a seal face where the part does not take impact.",
        "scope": "material"
      }
    ],
    "compare": "Chromia is hard and brittle. Its melting point is 2435 °C as bulk crystal, and a typical plasma sprayed coating has a Vickers hardness of 900 to 1200 HV300. The HTS technical table caps wear service at 540 °C. Adding titania to chromia makes the coating less brittle, according to the Oerlikon data sheet for a chromia-titania blend. The Oerlikon sheet does not give hardness values for the blend that can be compared here, so this profile compares only pure chromia figures.",
    "compare_rows": [
      {
        "label": "Melting point",
        "benchmark": "melting_point",
        "scope": "material"
      },
      {
        "label": "Vickers hardness (typical APS)",
        "benchmark": "vickers_hardness",
        "scope": "material"
      },
      {
        "label": "Maximum service temperature (wear)",
        "benchmark": "max_service_temp",
        "scope": "material"
      }
    ],
    "handling": [
      "The coating powder is not classed as hazardous by every source. The sources disagree, so read the supplier's safety data sheet for the exact product.",
      "Keep the powder dry and in its original container, and dry open containers in an oven before use (Oerlikon blend data sheet).",
      "Finish with diamond wheels, and plan the cost and lead time."
    ],
    "good_for": [
      "Wear on sliding and abrasive surfaces, such as seal faces and printing rolls. The HTS page says the coating outlasts steel in these duties.",
      "Corrosion in mild acid and alkali once the coating is sealed. The HTS page quotes 'hold up through 30-day immersion across pH 0-10'."
    ],
    "watch_out": [
      "Brittleness. Point impact chips the coating, and the HTS page says not to specify it for impact.",
      "Porosity. Standard plasma sprayed coatings run up to 5% porosity, and the Odhiambo paper ties higher porosity to lower bond strength.",
      "Temperature. The wear ceiling in the table is 540 °C and the sealed corrosive ceiling is 177 to 205 °C."
    ],
    "verdict": "Chromia is the hard, brittle choice for sliding wear and seal faces, and it works only if impact is kept out and the coating is sealed for chemistry.",
    "recipe": {
      "line": "Chromia is chromium(III) oxide, Cr2O3. It is made from chromite ore by converting it through sodium dichromate, which is reduced with sulfur at high temperature. The Metco 6156 feedstock used in the Odhiambo paper is a sintered and crushed powder.",
      "parts": [
        {
          "name": "Chromium",
          "symbol": "Cr",
          "role": "The oxide-forming metal. Chromium sits at the centre of the corundum framework that the oxide forms."
        },
        {
          "name": "Oxygen",
          "symbol": "O",
          "role": "Fills the close-packed oxide framework with chromium in its octahedral holes, which gives a hard, brittle ceramic."
        }
      ]
    },
    "risk_groups": [
      {
        "title": "For people",
        "lead": "Chromium(III) oxide is classed as hazardous by some sources and not by others. The sources disagree, so handle the powder as a possible sensitizer and reproductive hazard until your own safety data sheet says otherwise.",
        "points": [
          {
            "label": "The powder",
            "line": "PubChem's summary says the substance does not meet GHS hazard criteria for 57.8% (1112 of 1924) of all reports. The rest carry hazard statements H302, H317, H319 and H360."
          },
          {
            "label": "Stricter registrant entry",
            "line": "A Johnson Matthey classification for Katalco 71-5, a Grade 2 chromium(III) oxide, lists H314, H340, H350, H361 and H371 with the signal word Danger. That is a different product, but it shows how far classifications can differ."
          },
          {
            "label": "Powder dust",
            "line": "The Oerlikon blend data sheet advises a dry place and an original container. It does not give a dust exposure limit for chromia."
          }
        ],
        "level": 0,
        "verdict": "Classification differs between sources"
      },
      {
        "title": "If a coating fails",
        "lead": "These points describe the coating's own limits, not people's exposure.",
        "points": [
          {
            "label": "Impact",
            "line": "Chromia is brittle. Point impact or edge loading chips the coating, so the HTS page says to specify it for sliding, erosive and corrosive duty, not impact."
          },
          {
            "label": "Thickness",
            "line": "The HTS page says 'Thickness limited to roughly 25-30 mils on cylindrical work before residual stress risks spalling'."
          },
          {
            "label": "Temperature",
            "line": "The table sets the wear ceiling at 540 °C and the sealed corrosive ceiling at 177 to 205 °C."
          }
        ]
      },
      {
        "title": "Handling and storage",
        "points": [
          {
            "label": "Storage",
            "line": "Keep Metco 6485 powder in its original container in a dry location, and dry any open container in an oven before use. That data sheet is for a chromia-titania blend, not pure chromia."
          },
          {
            "label": "Finishing",
            "line": "Finishing needs diamond wheels, so the HTS page says to plan the cost and lead time."
          }
        ]
      }
    ]
  },
  "updated": "2026-11-02",
  "review": {
    "status": "draft",
    "method": "assistant",
    "checked_values": 19,
    "unreachable": 7,
    "caveats": 3,
    "note": "Written by an AI assistant on 2026-11-02 from fetched pages only; 19 benchmark values carry a source read in this run. Seven further sources were blocked or not found and are listed in gaps."
  },
  "sources": {
    "hts-chrome-oxide": {
      "title": "Chrome oxide thermal spray coating: technical data table, applications and sources (HTS Coatings)",
      "id": "HTS Coatings product page, /coatings/chrome-oxide",
      "url": "https://htscoatings.com/coatings/chrome-oxide",
      "year": 2026,
      "kind": "web",
      "license": "supplier web page, linked not reproduced"
    },
    "wikipedia-cr2o3": {
      "title": "Chromium(III) oxide, Wikipedia",
      "id": "Wikipedia article Chromium(III) oxide",
      "url": "https://en.wikipedia.org/wiki/Chromium(III)_oxide",
      "year": 2026,
      "kind": "web",
      "license": "CC BY-SA 4.0 (Wikipedia)"
    },
    "rokide-c-tds": {
      "title": "Rokide C (Chrome Oxide) ceramic rod for thermal spraying, Saint-Gobain Coating Solutions technical bulletin",
      "id": "Saint-Gobain Coating Solutions Rokide C bulletin, copy on Alloy Coating Supply",
      "url": "https://store.alloycoatingsupply.com/wp-content/uploads/2023/11/Rokide-C-Rods-Technical-Data-Sheet.pdf",
      "year": 2023,
      "kind": "datasheet",
      "license": "manufacturer document, linked not reproduced"
    },
    "odhiambo2021": {
      "title": "Influence of plasma spraying current on the microstructural characteristics and tribological behaviour of plasma sprayed Cr2O3 coating",
      "id": "doi:10.1016/j.bsecv.2020.03.007 (Bol. Soc. Esp. Ceram. Vidr. 60, 338-346, 2021)",
      "url": "https://www.elsevier.es/en-revista-boletin-sociedad-espanola-ceramica-vidrio-26-articulo-influence-plasma-spraying-current-on-S0366317520300340",
      "year": 2021,
      "kind": "paper",
      "license": "open access, as listed on the journal page"
    },
    "usgs-mcs2026-chromium": {
      "title": "Mineral Commodity Summaries 2026, Chromium",
      "id": "USGS MCS 2026, February 2026",
      "url": "https://pubs.usgs.gov/periodicals/mcs2026/mcs2026-chromium.pdf",
      "year": 2026,
      "kind": "report",
      "license": "public domain (USGS)"
    },
    "pubchem-cr2o3": {
      "title": "PubChem compound record, Chromium(III) oxide (CID 517277): GHS classification and experimental properties",
      "id": "CID 517277; CAS 1308-38-9",
      "url": "https://pubchem.ncbi.nlm.nih.gov/rest/pug_view/data/compound/517277/JSON",
      "year": 2026,
      "kind": "database",
      "license": "public domain (NCBI)"
    },
    "metco-6485-ds": {
      "title": "Chromium Oxide - Titanium Oxide Powders (Metco 6485), Oerlikon Metco data sheet DSM-0387.1",
      "id": "DSM-0387.1 (c) 2024 Oerlikon Metco",
      "url": "https://www.oerlikon.com/ecoma/files/DSM-0387_Cr2O3_40TiO2.pdf?download=true",
      "year": 2024,
      "kind": "datasheet",
      "license": "manufacturer document, linked not reproduced"
    },
    "jm-katalco-sds": {
      "title": "Cr - Chromium (III) Oxide C&L Katalco 71-5, classification and labelling (IUCLID 6 export)",
      "id": "Johnson Matthey C&L record, Grade 2 Chromium (III) Oxide, generated 11/12/2020",
      "url": "https://matthey.com/documents/161599/166998/Cr-Chromium-III-Oxide-Katalco-715.pdf/dcfbe5f7-6cc9-a7c9-0d92-7d2339ca4759",
      "year": 2020,
      "kind": "datasheet",
      "license": "registrant document, linked not reproduced"
    }
  },
  "license": "CC-BY-4.0",
  "url": "https://spacemushroom.com/profiles/chromium-oxide-coating/"
}