Cuprous Oxide (Red) Cu₂O · Red · CAS 1317-39-1
The highest copper loading of any fixed copper — 88.8% against 65% for the hydroxide and 59% for the oxychloride — and the active that still carries most of the world’s antifouling marine paint.
Chelora Chemicals is a cuprous oxide supplier and sourcing partner serving coatings formulators, agrochemical formulators and electronics buyers across the United States, with a batch COA, SDS and UN 3077 documentation on every consignment.
- CAS Number
- 1317-39-1
- Chemical name
- Copper(I) oxide
- Molecular formula
- Cu₂O
- Molecular weight
- 143.09 g/mol
- Copper as Cu (theoretical)
- 88.8%
- Appearance
- Red to reddish-brown powder
- Density
- 6.0 g/cm³
- Transport
- UN 3077 · Class 9 · PG III
- HS Code
- 2825 50
Note: copper loading is the whole commercial case. At 88.8% copper, Cu₂O delivers more copper per tonne than any other fixed copper — 65.1% for the hydroxide, 59.5% for the oxychloride, 79.9% for the cupric oxide. In an antifouling paint, where copper has to be loaded at high volume fraction without destroying the film, that density is not a nice-to-have. It is the reason the chemistry is used.
From copper to the red oxide
Cuprous oxide is the partially oxidized copper — one oxidation state below the black cupric oxide, and a different material entirely.
Why it matters: Cu₂O oxidizes to black CuO in moist air — so a consignment that arrives darkened has moved one oxidation state, and that is a quality failure, not weathering
What cuprous oxide is used for
Cuprous oxide is a red to reddish-brown powder, Cu₂O, and it is the copper(I) oxide — one oxidation state below the black cupric oxide that shares its common name. The two are not interchangeable and should never be ordered by the words "copper oxide" alone.
Its dominant commercial use worldwide is antifouling marine paint, where it is the biocide that stops barnacles, algae and tubeworms colonising a hull. It is also an EPA-recognized fungicide active, a red colorant in glass and ceramic glazes, a rectifier and photovoltaic material in electronics, and a catalyst. In the EU it is additionally authorised as a feed additive under the name dicopper oxide — which the black cupric oxide is not.
What the specification controls
- Copper as Cu, 88.8% theoretical. Commercial grades sit close to it; the assay is agreed per order.
- Cuprous versus cupric content. The parameter that matters most — Cu(I) oxidising to Cu(II) is the failure mode.
- Particle size. In antifouling paint it governs leach rate and film loading; in glass it governs color development.
- The black oxide, which is a different material: cupric oxide.
Handling character
Cuprous oxide is a Class 9 dangerous good and oxidizes in moist air. Full detail is in the Safety section below.
| Parameter | Typical value |
|---|---|
| Appearance | Red to reddish-brown powder |
| Copper as Cu | Per agreed specification |
| Theoretical Cu for pure Cu₂O | 88.8% |
| Cuprous oxide content | Per agreed specification |
| Moisture | Per grade specification |
| Particle size | Per agreed sieve specification |
Important: the figures above are indicative of commercial material and are offered for planning only. The batch certificate of analysis is the governing document.
| Property | Value |
|---|---|
| Physical state | Red to reddish-brown solid |
| Molecular weight | 143.09 g/mol |
| Density | 6.0 g/cm³ |
| Melting point | ≈ 1,232 °C |
| Water solubility | Insoluble |
| Oxidation in moist air | To black CuO |
| Copper content, theoretical | 88.8% |
Physical constants compiled from public reference data for CAS 1317-39-1 and rounded for readability. Commercial grades differ in particle size and in cuprous-to-cupric ratio, both of which affect performance more than the headline assay. Treat the table as orientation, not as a specification.
Where US industry uses cuprous oxide
Antifouling coatings above all, then crop protection, glass and electronics.
Antifouling marine coatings
The dominant global use. The biocide that stops barnacles, algae and tubeworms colonising a hull, loaded at high volume fraction.
- Particle size governs leach rate
- Low cupric content specified
- Consistent assay lot to lot
Fungicide formulation
An EPA-recognized copper fungicide active, formulated into granules and powders at the highest copper loading of the fixed coppers.
- Grindability confirmed
- Compare copper hydroxide
- Registration sits with the registrant
Glass, ceramics & glazes
The source of copper ruby red in glass and of red and metallic effects in ceramic glazes, where the oxidation state is the color.
- Low cupric content critical
- Particle size to specification
- Shade matched to retained sample
Electronics & semiconductors
A p-type semiconductor used historically in rectifiers and now in photovoltaic and sensor research.
- High purity grades on request
- Documented impurity profile
- Small quantities available
Catalysis & specialty chemistry
A catalyst and a copper(I) source in organic synthesis where the oxidation state is the point.
- Surface area to specification
- Consistent crystal form
- Technical desk review on request
Import & compliance coordination
End use decides the route: antifouling and fungicide uses are pesticidal under FIFRA; glass and electronics are not.
- End use confirmed before quoting
- UN 3077 documentation prepared
- Broker coordination on request
Delivered to US plants and ports
We ship cuprous oxide to nominated delivery points across the United States. The regions below are destinations we serve — Chelora Chemicals is a sourcing and supply partner, not a US manufacturer, and does not hold US stock.
Gulf Coast
The largest US chemical cluster, and the usual entry point for bulk consignments.
- Houston & Galveston, TX
- New Orleans & Baton Rouge, LA
- Mobile, AL
Northeast
Container and bulk delivery into the mid-Atlantic and New England manufacturing belt.
- Newark & Elizabeth, NJ
- Philadelphia, PA
- Boston, MA
Southeast
Port-side delivery for the Carolinas, Georgia and Florida processing plants.
- Savannah, GA
- Charleston, SC
- Jacksonville, FL & Norfolk, VA
Midwest & Great Lakes
Inland rail and truck forwarding from the nearest coastal port to the industrial Midwest.
- Chicago, IL
- Detroit, MI
- Cleveland & Columbus, OH
West Coast
Pacific routing for West Coast processors and formulators.
- Los Angeles & Long Beach, CA
- Oakland, CA
- Seattle & Tacoma, WA
Southwest & Mountain
Inland delivery to interior states, forwarded from the Gulf or Pacific gateway.
- Dallas–Fort Worth, TX
- Phoenix, AZ
- Denver, CO
Importing into the United States
Cuprous oxide is a TSCA-regulated chemical substance. Under TSCA section 13 the importer of record, or its authorized agent, must certify to US Customs and Border Protection that each shipment either complies with TSCA or is not subject to it. We confirm the substance's TSCA Inventory status and agree in writing who files that certification before the first consignment moves.
Which party carries that duty follows the Incoterm. On FOB, CFR or CIF terms it is usually the US buyer; on DDP terms it can be the seller or its agent. Safety data sheets and labels are supplied to OSHA's updated Hazard Communication Standard, and the UN 3077 Class 9 transport documentation is prepared before booking.
| Item | How it works |
|---|---|
| Delivery points | Any nominated US plant, terminal or port of discharge |
| Incoterms quoted | FOB · CFR · CIF · DDP |
| Importer of record | Agreed in writing before the first shipment |
| TSCA certification | Section 13 positive certification filed at entry |
| Documentation | Batch COA, SDS, packing list, certificate of origin |
| Pack formats | 25 kg bags or bulk bags |
Note: regional coverage describes where we deliver, not where we hold inventory. Lead time depends on producer scheduling and ocean transit to your nominated US port — we confirm both in the quotation.
How we supply cuprous oxide
Chelora Chemicals is a cuprous oxide supplier and sourcing partner, not a manufacturer. On this compound the risk is oxidation state: Cu₂O converts to black CuO in moist air, and a consignment that arrives darkened has lost the property you bought it for.
We place your order with whichever qualified producer best matches your specification, your price point and your delivery window, and confirm the US import and FIFRA position before booking.
We keep a second qualified source on this line, so a single-plant disruption never becomes your coating or formulation schedule problem.
- Cuprous-to-cupric ratio specified, not assumed. Oxidation to the black Cu(II) oxide is the failure mode on this compound and it is invisible in a total-copper assay.
- Color recorded at dispatch. Red is the Cu(I) state; darkening toward brown or black is the visible signal that it has oxidized.
- Particle size agreed up front. In antifouling it governs leach rate and film loading; in glass it governs color development. The two want different things.
- Moisture-barrier packaging as standard. Moist air drives the oxidation, so the pack is part of the specification rather than an afterthought.
- UN 3077 documentation prepared before booking. Class 9 on aquatic toxicity grounds; the paperwork is not optional.
- End use confirmed before quoting. Antifouling and fungicide uses are pesticidal under FIFRA and need a Notice of Arrival on import; glass and electronics do not.
Bagged or bulk bagged
25 kg bags, bulk bags or drums — all moisture-barrier and to UN 3077 marking requirements.
25 kg poly-lined bags
Moisture-barrier bags on stretch-wrapped pallets, UN-marked — the barrier matters on this compound.
500–1,000 kg bulk bags
Liner-fitted bulk bags for coatings and formulation plants.
Steel or fiber drums
Sealed drums where extended storage or maximum moisture protection is needed.
Small sealed units
Smaller sealed units for electronics, laboratory and pilot work.
Incoterms to suit you
Quoted on the Incoterm your purchasing team works to, with dangerous goods documentation filed before booking.
Trial / sample quantities
Small packs dispatched for paint loading, leach rate and color trials before a commercial order.
A Class 9 dangerous good — and it oxidizes
Cuprous oxide is harmful by ingestion and damaging to the eyes, and the classification that governs its logistics is aquatic toxicity — very toxic to aquatic life with long-lasting effects, which is what makes it a Class 9 dangerous good. The summary below is orientation only — the safety data sheet supplied with your specific batch is the authoritative document.
Classified hazards
H302Harmful if swallowed.H318Causes serious eye damage.H410Very toxic to aquatic life with long lasting effects.
US antifouling regulation, stated accurately as of this writing. Copper antifouling paint remains legal and in use in the United States. Washington State enacted a copper restriction in 2011, delayed it, and set a potential 2026 date for recreational boats — but the Department of Ecology’s January 2024 review concluded that safer, effective, feasible alternatives were not available, so the restriction will not take effect, with a follow-up report due by 30 June 2029. What does apply is the EPA leach-rate cap of 9.5 µg of copper per cm² per day, adopted in Washington in 2019 and matched by California DPR, plus local copper TMDLs in San Diego, Marina del Rey and Newport Bay. Confirm the current position for your market with counsel; this area moves.
Storage
Store in sealed, moisture-barrier packaging in a cool, dry, well-ventilated area away from acids and oxidizers. Moisture is the controlling variable: Cu₂O oxidizes to black CuO in moist air, so a broken seal or a damp warehouse costs you the oxidation state you paid for. Bunded or contained storage is advised because of the aquatic hazard.
Handling
Handle with dust control, impervious gloves and tight-fitting eye protection; the material causes serious eye damage and is harmful if swallowed. Prevent any release to drains, watercourses or soil. Follow the exposure controls set out in the batch SDS.
Transport
Copper oxides are classified as dangerous goods for transport on the basis of aquatic toxicity, normally shipped as UN 3077, Environmentally hazardous substance, solid, n.o.s., Class 9, Packing Group III. Marked and labeled packaging, a dangerous goods declaration and IMDG or DOT-compliant documentation are required. We confirm and document the classification for your specific grade, packaging and destination before booking.
Every batch, documented
We verify documentation before dispatch so there are no surprises at your incoming-goods bench.
Specification agreed
Copper content basis, crystal form, shade, particle size and moisture confirmed against your requirement before order placement.
Producer batch testing
The producing plant tests each batch against the agreed specification before release.
Documentation review
COA, SDS, TSCA or FIFRA position and UN 3077 dangerous goods paperwork checked by our desk before the shipment is booked.
Traceable dispatch
Each shipment is traceable to its producing batch, with full chain-of-custody records on request.
How cuprous oxide is made
Cuprous oxide is produced by routes that hold copper in the +1 oxidation state — electrolytic processes on copper, controlled reduction of copper(II) compounds, or controlled high-temperature oxidation of copper metal. Whichever route, the engineering problem is the same: Cu(I) is the intermediate state, and it wants to go further.
That instability is the commercial story of this compound. In moist air Cu₂O oxidizes to CuO, the black copper(II) oxide — which is a different product with a different CAS number, a different color and a lower copper content. The conversion shows itself as darkening from red toward brown and black, so color is a condition signal here in the same way it is on copper hydroxide.
For antifouling service the particle size distribution does as much work as the assay. The paint film releases copper by dissolution at the exposed surface, so size and shape govern the leach rate — and in the United States that leach rate is itself regulated, capped at 9.5 µg per cm² per day.
We do not publish operating process parameters here; this is background only. Full technical documentation accompanies every shipment, and any process-specific detail you need is best confirmed directly with our technical desk.
| Chemical family | Copper(I) oxide |
|---|---|
| Copper content | 88.8% — highest of the fixed coppers |
| Color | Red to reddish-brown |
| Failure mode | Oxidizes to black CuO in moist air |
| Dominant use | Antifouling marine coatings |
| Not the same as | Cupric oxide, CuO, CAS 1317-38-0 |
The copper range and related inorganics
The other copper chemistries and the acids and salts supplied from the same desk.
Cuprous oxide, answered
What is the difference between cuprous and cupric oxide?
What is cuprous oxide used for?
Why does cuprous oxide carry more copper than the other fixed coppers?
Is copper antifouling paint still legal in the United States?
Why does the color matter?
What particle size should I specify?
Is cuprous oxide used as a feed additive?
Is cuprous oxide hazardous?
Can I import this into the United States?
Do you manufacture this yourself?
Get a quote on cuprous oxide
Send us your required copper assay, cuprous-to-cupric specification, particle size, pack size and US delivery point — and tell us the end use, because antifouling and fungicide uses are pesticidal under FIFRA and glass and electronics are not.