Hexavalent Chromium laser cleaning visualization showing process effects
Todd Dunning
Todd DunningMAUnited States
Optical Materials for Laser Systems
Published
Jan 6, 2026

Hexavalent Chromium Compound

Chromium Vi Compound safety information for laser cleaning. Health hazards, exposure limits, and protective equipment requirements.

Chemical Properties

Chemical Identity

CAS Number
18540-29-9
Formula
Cr(VI)
Molecular Weight
52 g/mol

Exposure Limits Comparison

Health Effects

Lung Cancer
Yes
Respiratory Irritation
Yes
Skin Ulceration
Yes
Nasal Septum Perforation
Yes
Detection Monitoring
SensorTypes
  • Particulate monitors
  • Personal air sampling pumps
  • Area monitors
  • Colorimetric detection
DetectionRange
0.0001-100 µg/m³
AlarmSetpoints
Low
0.2 µg/m³ (NIOSH REL certain compounds)
High
5 µg/m³ (OSHA PEL)
Evacuate
15 mg/m³ (15,000 µg/m³) (NIOSH IDLH)
ColorimetricTubes
  • Dräger Chromium VI 0.1/a
  • Gastec 171
AnalyticalMethods
MethodTechniqueDetectionLimit
NIOSH 7600Visible absorption spectrophotometry0.02 µg/sample
NIOSH 7605Ion chromatography0.05 µg/sample
OSHA ID-215Visible spectrophotometry0.05 µg/sample
OdorThreshold
Not applicable - no warning odor at hazardous levels
Environmental Impact
AquaticToxicity
Very toxic to aquatic life. LC50 (fish, 96h): 10-100 mg/L depending on species. Cr(VI) more toxic than Cr(III).
Biodegradability
Not biodegradable. Cr(VI) can be reduced to less toxic Cr(III) by organic matter and reducing conditions.
Bioaccumulation
Low bioaccumulation potential. Does not concentrate in food chain.
SoilMobility
High mobility in soil and groundwater as Cr(VI). Adsorbs less than Cr(III). Contaminates wells.
AtmosphericFate
Settles as particulate. Does not react in atmosphere. Washed out by rain.
OzoneDepletion
false
ReportableReleases
Water
5000 lbs to navigable waters
Air
5000 lbs/day (CERCLA RQ for soluble Cr(VI))
Ppe Requirements
Respiratory
NIOSH-approved air-purifying respirator with P100 filters for ≤2.5 µg/m³. Powered air-purifying respirator (PAPR) for ≤12.5 µg/m³. SCBA for >12.5 µg/m³ or unknown concentrations.
Eye Protection
Chemical safety goggles, face shield for dusty/spray operations
Skin Protection
Nitrile or neoprene gloves (>4mil thickness). Chemical-resistant clothing. Cr(VI) can cause allergic skin reactions and ulcerations.
Reactivity
Stability
Stable under normal conditions. Some compounds decompose when heated.
Polymerization
Will not polymerize
IncompatibleMaterials
  • Strong reducing agents
  • Combustible materials
  • Organic materials
  • Acids with metals
  • Bases
  • Ammonia
  • Sulfur
  • Phosphorus
HazardousDecomposition
  • Chromium oxides
  • Toxic fumes
  • Oxygen (chromates)
ConditionsToAvoid
  • Heat
  • Incompatible materials
  • Moisture (some compounds)
  • Shock (chromates)
ReactivityHazard
STRONG OXIDIZER. Reacts violently with combustible materials, reducing agents. Chromates may explode when heated. Corrosive to skin and metals.
Regulatory Classification
UnNumber
UN3288 (Toxic solid, inorganic, n.o.s.) or UN1755 (Chromic acid solution)
DotHazardClass
6.1 (Toxic) or 8 (Corrosive)
DotLabel
Toxic or Corrosive
NfpaCodes
Health
3
Flammability
0
Reactivity
1
Special
OX (Oxidizer)
EpaHazardCategories
  • Carcinogenicity
  • Acute toxicity
  • Skin corrosion
  • Respiratory sensitization
  • Aquatic toxicity
SaraTitleIii
true
CerclaRq
5000 pounds (2270 kg) for soluble Cr(VI) compounds
RcraCode
D007 (chromium)

Contaminants That Produce Hexavalent Chromium

Hexavalent Chromium is produced during laser ablation of stainless steel weld heat tint, chromate conversion coatings, and chromium-containing paints. It is a Group 1 carcinogen. Laser cleaning of chromium-containing materials requires HEPA exhaust, continuous Cr(VI) monitoring, and respiratory protection to maintain exposures below 5 μg/m3 OSHA PEL.
No metadata available

Chromium Oxide Pitting

No metadata available

Steel Surface Corrosion

No metadata available

Paint Residue / Coating Failure Laser Cleaning

No metadata available

Chemical Conversion Coating

Chemical Properties

Molecular formula, CAS number, molecular weight, and chemical structure
Type
chemical_properties
Id
chromium-vi-physical-data

Physical Properties

Chemical and physical characteristics
BoilingPoint
Varies by compound (chromic acid: decomposes >250°C)
MeltingPoint
Varies by compound
VaporPressure
Negligible at room temperature
VaporDensity
Not applicable (metal/salt)
SpecificGravity
Varies (chromic acid: 1.2)
FlashPoint
Not applicable
AutoignitionTemp
Not applicable
ExplosiveLimits
Not applicable
Appearance
Yellow to orange-red crystalline solid (chromates), green solution (chromic acid)
Odor
Odorless or faint acrid odor

Alternative Names

Synonyms and chemical identifiers
Synonyms
  • Hexavalent chromium
  • Cr(VI)
  • Chromate
  • Chromic acid
  • Potassium dichromate
  • Sodium chromate
CommonTradeNames
  • Chrome plating chemicals
  • Chromate conversion coatings
OtherIdentifiers
RtecsNumber
GB6200000 (chromic acid)
EcNumber
231-889-5 (chromium trioxide)
PubchemCid
24425

Health Effects

Adverse health impacts from exposure to this compound
Route
inhalation
Effect
Respiratory tract irritation and ulceration; increased risk of lung cancer
Severity
severe
Onset
immediate for irritation; long-term for cancer
Route
skin_contact
Effect
Allergic dermatitis and chrome ulcers (perforations in nasal septum or skin)
Severity
high
Onset
short-term
Route
eye_contact
Effect
Severe conjunctivitis, corneal damage, and potential vision impairment
Severity
severe
Onset
immediate
Route
ingestion
Effect
Gastrointestinal hemorrhage, renal failure, and systemic toxicity
Severity
severe
Onset
short-term

Personal Protective Equipment

Required safety equipment for handling this compound
Respiratory
NIOSH-approved air-purifying respirator with P100 filters for ≤2.5 µg/m³. Powered air-purifying respirator (PAPR) for ≤12.5 µg/m³. SCBA for >12.5 µg/m³ or unknown concentrations.
Skin
Nitrile or neoprene gloves (>4mil thickness). Chemical-resistant clothing. Cr(VI) can cause allergic skin reactions and ulcerations.
Eye
Chemical safety goggles, face shield for dusty/spray operations
MinimumLevel
Level C for known concentrations <2.5 µg/m³, Level B for higher concentrations or welding/cutting operations
SpecialNotes
CARCINOGEN and ALLERGEN. Prevent skin contact - causes sensitization. Welding/cutting stainless steel generates Cr(VI) fume. Use wet methods to control dust. Medical surveillance required.

Exposure Limits

OSHA, NIOSH, and ACGIH exposure thresholds
OshaPelMgM3
0.005
NioshRelMgM3
0.001
AcgihTlvMgM3
0.0002
WorkplaceExposure
OshaPel
twa8Hr: 0.005 mg/m³
stel15Min: null
ceiling: null
NioshRel
twa8Hr: 0.0002 mg/m³
stel15Min: null
ceiling: null
idlh: 15 mg/m³ (as Cr(VI))
AcgihTlv
twa8Hr: 0.0002 mg/m³
stel15Min: null
ceiling: null
BiologicalExposureIndices
0: [object Object]
1: [object Object]

Storage Requirements

Safe storage conditions and compatibility
TemperatureRange
Store at room temperature, avoid excessive heat
Ventilation
Local exhaust ventilation. Store in well-ventilated area away from work areas.
Incompatibilities
  • Combustible materials
  • Organic materials
  • Reducing agents
  • Acids
  • Bases
  • Ammonia
  • Hydrogen sulfide
ContainerMaterial
Tightly sealed glass or plastic containers. Polyethylene or glass for chromic acid.
Segregation
Separate from combustibles, organics, and reducing agents by 20 feet or firewall. Designated carcinogen storage.
QuantityLimits
Minimize quantities stored. OSHA requires carcinogen storage protocols.
SpecialRequirements
Post "CANCER HAZARD" and "STRONG OXIDIZER" signs. Restrict access to authorized personnel. Secondary containment for liquids. Inspect weekly for container integrity. Emergency eyewash/shower within 10 seconds.

Emergency Response

Procedures for spills, exposure, and incidents
FireHazard
Non-combustible. Strong oxidizer - increases fire intensity. Chromates may explode when heated with organic materials.
FireSuppression
Use agent appropriate for surrounding fire. Do not use water on dichromate fires. Wear SCBA.
SpillProcedures
Evacuate area. Wear full PPE. Avoid dust generation. Reduce Cr(VI) to Cr(III) with sodium bisulfite or ferrous sulfate before cleanup. Sweep/vacuum with HEPA filter. Dispose as hazardous waste. Decontaminate area thoroughly.
ExposureImmediateActions
Remove contaminated clothing immediately. Wash skin with soap and water for 15 minutes. If inhaled, move to fresh air. Seek medical attention immediately - inform physician of Cr(VI) exposure and potential for delayed effects.
EnvironmentalHazards
Toxic to aquatic life. Cr(VI) is highly mobile in groundwater. Can contaminate drinking water. Report releases >5000 lbs.
SpecialHazards
KNOWN HUMAN CARCINOGEN (IARC Group 1). Causes lung cancer, nasal septum perforation. Strong oxidizer - reacts violently with combustibles. Corrosive to skin (ulcers/chrome holes). Potent allergen - can cause severe dermatitis.

Regulatory Classification

DOT, UN, and NFPA hazard classifications
UnNumber
UN3288 (Toxic solid, inorganic, n.o.s.) or UN1755 (Chromic acid solution)
DotHazardClass
6.1 (Toxic) or 8 (Corrosive)
DotLabel
Toxic or Corrosive
NfpaCodes
Health
3
Flammability
0
Reactivity
1
Special
OX (Oxidizer)
EpaHazardCategories
  • Carcinogenicity
  • Acute toxicity
  • Skin corrosion
  • Respiratory sensitization
  • Aquatic toxicity
SaraTitleIii
true
CerclaRq
5000 pounds (2270 kg) for soluble Cr(VI) compounds
RcraCode
D007 (chromium)

Environmental Impact

Toxicity, biodegradability, and environmental fate
AquaticToxicity
Very toxic to aquatic life. LC50 (fish, 96h): 10-100 mg/L depending on species. Cr(VI) more toxic than Cr(III).
Biodegradability
Not biodegradable. Cr(VI) can be reduced to less toxic Cr(III) by organic matter and reducing conditions.
Bioaccumulation
Low bioaccumulation potential. Does not concentrate in food chain.
SoilMobility
High mobility in soil and groundwater as Cr(VI). Adsorbs less than Cr(III). Contaminates wells.
AtmosphericFate
Settles as particulate. Does not react in atmosphere. Washed out by rain.
OzoneDepletion
false
ReportableReleases
Water
5000 lbs to navigable waters
Air
5000 lbs/day (CERCLA RQ for soluble Cr(VI))

FAQ

Common Questions and Answers
As a laser cleaning operator working on chromium-containing alloys like stainless steel, what personal protective equipment (PPE) should I use to minimize Cr(VI) exposure risks?
Always wear a NIOSH-approved respirator with a P100 filter or supplied-air system to protect against inhaling Cr(VI) fumes or aerosols generated during laser ablation, as Cr(VI) is a potent carcinogen that can cause lung cancer via respiratory exposure. In addition, use chemical-resistant gloves, full-body coveralls, and safety goggles to prevent skin contact, which can lead to dermatitis or ulceration, and ensure the workspace has local exhaust ventilation to capture airborne particles. Regularly inspect and replace PPE, and follow OSHA's permissible exposure limit of 5 µg/m³ for Cr(VI) over an 8-hour shift to stay within safe thresholds.

Detection & Monitoring

Methods for detecting and measuring this compound
SensorTypes
  • Particulate monitors
  • Personal air sampling pumps
  • Area monitors
  • Colorimetric detection
DetectionRange
0.0001-100 µg/m³
AlarmSetpoints
Low
0.2 µg/m³ (NIOSH REL certain compounds)
High
5 µg/m³ (OSHA PEL)
Evacuate
15 mg/m³ (15,000 µg/m³) (NIOSH IDLH)
ColorimetricTubes
  • Dräger Chromium VI 0.1/a
  • Gastec 171
AnalyticalMethods
  • [object Object]
  • [object Object]
  • [object Object]
OdorThreshold
Not applicable - no warning odor at hazardous levels

Reactivity

Chemical reactivity and incompatibilities
Stability
Stable under normal conditions. Some compounds decompose when heated.
Polymerization
Will not polymerize
IncompatibleMaterials
  • Strong reducing agents
  • Combustible materials
  • Organic materials
  • Acids with metals
  • Bases
  • Ammonia
  • Sulfur
  • Phosphorus
HazardousDecomposition
  • Chromium oxides
  • Toxic fumes
  • Oxygen (chromates)
ConditionsToAvoid
  • Heat
  • Incompatible materials
  • Moisture (some compounds)
  • Shock (chromates)
ReactivityHazard
STRONG OXIDIZER. Reacts violently with combustible materials, reducing agents. Chromates may explode when heated. Corrosive to skin and metals.

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