Lubricant Additive Components
CheMost supplies extreme pressure (EP) additives for gear oils, greases, metalworking fluids and industrial lubricants — the sulfur, phosphorus and ashless chemistries that stop metal welding and scoring under the heaviest loads.
These are EP additive components for lubricant formulators. The range spans the full EP toolbox: sulfur carriers (sulfurized isobutylene, sulfurized olefin), an ashless multifunctional dithiocarbamate, and a phosphorus-sulfur phosphorothioate. The first decision — active versus inactive sulfur — is below, then choose a chemistry and open a product page for documentation.
Browse CheMost Extreme Pressure Additives
Start with the product family that best matches your formulation target. Each product page goes deeper into the exact grade, properties, and documentation.
How EP Additives Work — and EP vs Anti-Wear
When a gear or bearing runs slow and heavily loaded, the oil film collapses and metal asperities touch — the boundary regime, where adhesive wear and, in the extreme, welding and scoring occur. EP additives are the last line of defence: under the heat and pressure of contact they react with the steel to form a metal-compound film (iron sulfide, iron phosphide) that shears far more easily than the metal junction itself, so the surfaces slide instead of welding.
This is also the line between EP and anti-wear (AW) additives: AW additives work at lower loads and temperatures to slow everyday wear, while EP additives activate at the higher temperatures of severe contact to prevent catastrophic seizure. They are complementary — most gear and many industrial oils use both, balanced against each other and against corrosivity.
The Key Decision: Active vs Inactive Sulfur
For the sulfur-carrier EP additives, the single most important choice is how active the sulfur is — and it is a direct trade-off:
- Active sulfur reacts readily at lower temperatures to build a strong EP film — ideal for heavy-duty steel cutting and high-load gears. The cost is that it also attacks yellow metals (copper, brass, bronze), so it is unsuitable, or needs careful inhibition, where those metals are present.
- Inactive sulfur releases its sulfur only at higher temperatures, so it is gentle on yellow metals and also contributes antioxidancy — the right choice for greases with brass cages, multi-metal systems and long-life oils, at the cost of lower peak EP.
Activity is measured against copper (ASTM D1662), and yellow-metal corrosion is checked with the copper-strip test (ASTM D130). Active grades can be masked with a metal deactivator, but the sulfur turns aggressive again once the deactivator is consumed — so where copper matters, the safer route is an inactive carrier. This is the question to settle before picking a product.
EP Chemistry Families — Where Each Fits
CheMost covers the three EP routes that a formulator actually chooses between:
- Sulfur carriers — the EP workhorses (sulfurized isobutylene, olefins, polysulfides). Highest load-carrying; the choice for gear oils and heavy-duty metalworking. EP and lubricity rise with polarity (olefin < ester < triglyceride).
- Phosphorus (phosphorothioate) — forms iron-phosphide films; strong anti-wear with mild EP, low odor and ashless — favoured in industrial gear, turbine and hydraulic oils, often paired with a sulfur carrier.
- Ashless dithiocarbamate — a metal-free multifunctional additive combining AW/EP with antioxidancy in one molecule, for clean, low-ash formulations.
The CheMost Range — How to Choose
Start with the metals in your system (active sulfur for all-steel, inactive/phosphorus/dithiocarbamate where copper is present), then match the chemistry to the load and application.
Sulfur carriers — maximum load-carrying
Sulfurized Isobutylene (SIB)
Type: High-sulfur sulfurized isobutene (~40–50% S).
Best for: The classic automotive and industrial gear-oil EP — high load-carrying at low corrosivity, in closed systems where its odor is contained.
Sulfurized Olefin
Type: Sulfurized olefin.
Best for: Industrial and metalworking EP where a versatile, well-known sulfurized-olefin profile is wanted.
Ashless & phosphorus — multi-metal and low-ash
Methylenebis(dibutyldithiocarbamate)
Type: Ashless, metal-free multifunctional dithiocarbamate.
Best for: Combined AW/EP and antioxidancy in one molecule, for clean low-ash and multi-metal formulations.
Triphenyl Phosphorothioate (TPPT)
Type: Ashless phosphorus-sulfur.
Best for: Strong anti-wear with mild EP in industrial gear, turbine and hydraulic oils — gentle on yellow metals, often paired with a sulfur carrier.
Treat Rate & Synergy
EP additives are usually dosed to a target sulfur (or phosphorus) level rather than a fixed percentage, and they are most effective in combination:
- Build the system, not a single additive. Sulfur carriers work synergistically with ZDDP and with overbased calcium/sodium sulfonates (the “passive EP” effect), and with phosphorus AW — combining them covers a wider load and temperature range than any one alone.
- Replacing chlorinated paraffins. A reactive sulfur carrier (for activity) plus a polar inactive carrier or ester (for lubricity) is the standard chlorine-free route to match chlorinated-paraffin performance in metalworking, without the HCl-corrosion and disposal issues.
The mechanisms, active-sulfur behaviour and test methods above are industry and textbook references. The right chemistry, sulfur/phosphorus level and combinations depend on your base oil, metallurgy and load — CheMost can advise on selection and a starting point on request.
Common Applications
- Automotive & industrial gear oils: high load-carrying and anti-scoring — SIB and sulfur-carrier/phosphorus combinations, including hypoid and worm gears.
- Metalworking fluids: cutting and forming of steel — active sulfur carriers for activity, polar grades for lubricity, as chlorinated-paraffin replacements.
- Greases: load-bearing protection — inactive sulfur carriers and ashless chemistries where brass cages and yellow metals are present.
- Slideway & hydraulic oils: mild EP and anti-wear, often phosphorus or ashless multifunctional.
- Engine oils: anti-wear and supplementary EP within the additive package.
Need help choosing an EP additive?
Tell us your application, the load and temperature, the metals in contact (especially any yellow metals), and whether you are replacing a chlorinated paraffin. We will point you to the right sulfur, phosphorus or ashless chemistry — and the synergy combination — then share the relevant technical documents.
Request a Sample Get a QuoteEP additives are specified across Industrial Lubricant, Automotive Lubricant and Metalworking formulations, paired with ZDDP anti-wear additives, friction modifiers and protected by metal deactivators where yellow metals are present. For deeper background see our notes on EP additives for metalworking beyond chlorinated paraffins and the anti-wear additive glossary entry.
Quick Reference
What is an extreme pressure (EP) additive?
An EP additive is a component that protects metal under very high loads, when the oil film has collapsed and surfaces would otherwise weld or score. Under the heat and pressure of contact it reacts with the steel to form a metal-compound film (iron sulfide or iron phosphide) that shears easily, letting the surfaces slide instead of seizing. EP additives are used in gear oils, greases and metalworking fluids.
What is the difference between EP and anti-wear additives?
Both protect in boundary lubrication, but at different severities. Anti-wear (AW) additives act at lower loads and temperatures to slow everyday wear; EP additives activate at the higher temperatures of severe contact to prevent welding and scoring. They are complementary, and most gear and many industrial oils use both together.
Active or inactive sulfur — which do I need?
Active sulfur reacts readily and gives the strongest EP, but it corrodes yellow metals (copper, brass, bronze) — so it suits all-steel, heavy-duty cutting and high-load gears. Inactive sulfur is gentle on yellow metals and adds antioxidancy, so it suits greases with brass cages, multi-metal systems and long-life oils, at lower peak EP. Where copper is present, choose an inactive carrier (or pair an active one with a metal deactivator, accepting it becomes aggressive once the deactivator is used up).
Why is sulfurized isobutylene (SIB) only for closed systems?
SIB is the standard gear-oil EP because it carries high sulfur (around 40–50%) at relatively low corrosivity. Its drawback is a strong odor, which is no problem in a sealed gear box but unacceptable in open lubrication. For open or grease systems, lower-odor sulfurized olefins, inactive carriers or ashless chemistries are used instead.
Can EP additives replace chlorinated paraffins?
Yes. The standard chlorine-free route pairs a reactive sulfur carrier (for activity) with a polar inactive carrier or ester (for lubricity), which together approach chlorinated-paraffin performance in metalworking — without the hydrochloric-acid corrosion and waste-disposal concerns. The exact pair depends on the operation; our team can advise.
How are EP additives dosed?
They are usually formulated to a target sulfur (or phosphorus) level rather than a single fixed percentage, and they perform best in combination — sulfur carriers with ZDDP, overbased sulfonates and phosphorus AW to cover a wider load and temperature range. The right level and combination depend on your base oil, metallurgy and load; validate against the relevant bench tests, and our team can suggest a starting point.
Explore Other Additive Components
Every CheMost additive component, at a glance. Build a complete formulation — open any family to see its full product range, grades, and treat rates.