Cobalt Octoate (CAS 136-52-7)
| CAS No. | 136-52-7 |
|---|---|
| Alias | Cobalt 2-ethylhexanoate, Cobalt(II) 2-ethylhexanoate, Cobalt bis(2-ethylhexanoate) |
| Category | Driers |
| Packaging | 25 kg / 200 kg |
Grade PID A | Metal content 8±0.2%. Used as a surface drier in alkyd paints, oil-based coatings, and printing inks to accelerate oxidation and polymerization.
Introduction
Cobalt octoate is the most active drying catalyst in common use, and for all the pressure on cobalt it remains the benchmark that every alternative is measured against. It works by catalysing the oxidative crosslinking of alkyd and oil-based resins, and it does so at loadings of 0.1–0.5% on resin solids where other metals need several times more.
This grade is supplied as an 8.0 ± 0.2% cobalt solution in 200# solvent oil. It is a clear purple liquid with a neutral odour, which matters in clear varnishes where a coloured or smelly drier would show.
Physical & Chemical Properties
Clear purple liquid. Metal content 8.0 ± 0.2% Co. Molecular formula C16H30CoO4. Density 0.99–1.02 g/cm³ at 20 °C, viscosity 150–250 mPa·s at 25 °C, flash point ≥40 °C closed cup, acid value ≤15 mg KOH/g, moisture ≤0.1%.
Applications
Surface drier in alkyd paints, oil-based coatings and printing inks. Typical dosage 0.1–0.5% on resin solids; mix thoroughly before use. Often combined with a zirconium or calcium auxiliary to improve through-dry and reduce the cobalt requirement.
Regulatory status: what is and is not true about cobalt driers
There is no EU ban on cobalt driers. The 2018 ECHA restriction proposal covered five inorganic cobalt salts, not cobalt carboxylates, and the Commission terminated it in April 2022. No cobalt substance appears on the REACH Authorisation List, and Commission document COM(2025) 418 records the position plainly: no existing restrictions, no existing authorisations.
What does bite is 2-ethylhexanoic acid and its salts, the acid this drier is built on. It carries a harmonised Repr. 1B classification under CLP entry 607-230-00-6 and was brought into Annex XVII Appendix 6 by Commission Regulation (EU) 2023/1132, applying from 1 December 2023, restricting supply to the general public. The practical consequence is not that you cannot buy cobalt octoate. It is that the finished paint now carries H360D labelling, and that is a change worth telling your customers about before they find it themselves.
A separate development is worth tracking rather than acting on. Proposed occupational exposure limits of 0.01 mg/m³ inhalable and 0.0025 mg/m³ respirable are in the legislative process under CMRD 6. Those are a proposal. No EU cobalt OEL has been adopted. Cobalt octoate itself has no harmonised CLP classification, so the hazard data on its SDS is the supplier's own.
In the United States the position is more straightforward: 21 CFR 175.300(b)(3)(xxii) expressly lists cobalt octoate among permitted drier metal/acid combinations.
Transport classification is UN 1268, Class 3, Packing Group III. That comes from the mineral spirits carrier, not from the metal carboxylate.
Handling & Storage
Flammable liquid. Store cool, dry and well ventilated, away from heat and ignition sources, container tightly closed. Mix thoroughly before use. Consult the SDS.
Packaging
25 kg and 200 kg plastic or internally coated iron drums. Shelf life 12 months sealed in the original container. COA and SDS supplied with every shipment.
Applications & Industries
Coatings & Paints
Metal driers (cobalt, manganese, zirconium octoate, naphthenates) and photoinitiators for coatings, paints, varnishes and industrial finishes — with COA & MSDS per batch.
Paints & Varnishes Driers
Metal soap driers for alkyd and oil-based paints: cobalt, manganese, zirconium, cerium octoates and naphthenates with verified metal content, COA & MSDS per batch.
Related Products
Cobalt Octoate (PID B)
Manganese Octoate
Cobalt Naphthenate
Cobalt Naphthenate (PID B-1)
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