Technical Specifications
This grade family is available as 2 CheMost grades — the differences are in the columns below.
| Property | Unit | SPZS-S1 | SPZS-L1 | Test Method |
|---|---|---|---|---|
| Appearance | Colorless or light yellow liquid | Colorless or light yellow liquid | Visual | |
| Density at 20°C | kg/m³ | 1105 | 1135 | ASTM D4052 |
| Viscosity at 100°C | mm²/s | 15 | 18 | ASTM D445 |
| pH | 5.3 | 5.5 | ASTM D1293 | |
| Flash point | °C | 208 | 208 | ASTM D93 |
| Sulphur | % | 15.5 | 15.2 | ASTM D4951 |
| Phosphorus | % | 7.2 | 7.2 | ASTM D4951 |
| Zinc | % | 8.55 | 8.55 | ASTM D4951 |
| Color | 0.5 | 0.5 | ASTM D1544 | |
| Moisture content | % | 0.03 | 0.03 | ASTM D95 |
| Mechanical impurities | % | 0.03 | 0.03 | ASTM D473 |
| Solubility (Group I–III / PAO) | >20% / >10% | >20% / >10% | — |
* Typical values from batch production. Batch-specific COA available on request.
Technical content reviewed by the CheMost additives team · Specifications last reviewed
Molecular Structure
Molecular structure · zinc dithiophosphate
Zn[(RO)₂PS₂]₂ — R = C₄/C₈ primary alkyl
A zinc cation coordinated by two O,O-dialkyl dithiophosphate ligands; in these grades the alkyl groups are C4/C8 primary.
What Is Zinc Dialkyldithiophosphate (Primary Alkyl)?
CheMost supplies a primary-alkyl zinc dialkyldithiophosphate (ZDDP) — the multifunctional zinc-phosphorus antiwear additive that is the workhorse of engine-oil and industrial-lubricant formulation. It is an organometallic compound built around a zinc centre coordinated by two O,O-dialkyl dithiophosphate ligands; in these grades the alkyl groups are C4/C8 primary alkyl, which gives the molecule its thermal and hydrolytic stability.
One molecule does three jobs at once: it forms a protective antiwear film on rubbing metal surfaces, it acts as an antioxidant by decomposing the peroxides that age the oil, and it inhibits corrosion of bearing metals — all at low cost. That multifunctionality is why ZDDP has been the dominant antiwear chemistry in lubricants for more than fifty years.
CheMost offers two primary-alkyl grades on this page: SPZS-S1, the standard C4/C8 primary grade with good thermal stability, particularly suited to internal-combustion engine oils; and SPZS-L1, a long-chain C4/C8 primary grade with excellent thermal, oxidation and hydrolytic stability for high-grade turbocharged engine oils and antiwear hydraulic oils. Both carry the same phosphorus (7.2%) and zinc (8.55%) — the difference is the stability tier, set out in the Technical Specifications above and in the selection guide below.
How Primary-Alkyl ZDDP Works
Antiwear tribofilm formation
Under boundary and mixed lubrication — when the oil film thins enough for surface asperities to touch — ZDDP decomposes at the hot contact and builds a layered protective film: an iron-sulfide anchor against the metal, a load-bearing zinc/iron polyphosphate “glass” layer that shears in place of the metal, and an outer organic layer. The film is continuously removed by rubbing and replenished by fresh ZDDP in the oil, so wear protection self-renews until the additive depletes.
Antioxidant (peroxide decomposer)
ZDDP interrupts the radical chain that oxidises base oil by decomposing hydroperoxides before they propagate, slowing the oil thickening and acid formation that shorten oil life. This secondary antioxidant role is why a ZDDP-containing package often needs less supplementary antioxidant than a phosphorus-free system.
Corrosion inhibition
The dithiophosphate groups adsorb onto copper and bearing alloy surfaces to form a passivating layer that resists attack by the acidic by-products of combustion and oil oxidation, protecting bearings and other yellow-metal components.
Primary-alkyl stability
Primary-alkyl ZDDP forms a thermally and hydrolytically stable film, which makes it the preferred class for long-drain and high-temperature oils. The long-chain SPZS-L1 grade extends that stability further — more resistant to high temperature and to hydrolysis where moisture is present.
Choosing Between SPZS-S1 and SPZS-L1
Both grades are C4/C8 primary-alkyl ZDDP with identical phosphorus (7.2%) and zinc (8.55%), so they deliver the same antiwear film chemistry and the same phosphorus loading per unit treat. The choice is about the stability tier and the operating environment, not about antiwear strength:
SPZS-S1 — standard primary. Good thermal stability, light and almost colorless, with good oil solubility. The cost-effective default, particularly suited to internal-combustion engine oils and general industrial antiwear and grease applications where the sump does not run unusually hot and water exposure is low.
SPZS-L1 — long-chain primary. A higher-molecular-weight grade (density 1135 vs 1105 kg/m³, viscosity 18 vs 15 mm²/s) that is more stable at higher temperatures and, importantly, not easily hydrolysed — it carries explicit hydrolytic stability. Choose it for high-grade turbocharged engine oils, antiwear hydraulic oils and marine lubricants, and anywhere the oil runs hot or can pick up moisture, where the standard grade would deplete or hydrolyse faster.
Because both grades are primary-alkyl, they are tuned for thermal and hydrolytic durability rather than the fastest possible film build. Where an application specifically needs very rapid, low-temperature film formation — flat-tappet break-in, for example — that is the niche normally served by a secondary-alkyl ZDDP; for the stability and long-drain durability that most finished oils require, a primary grade is the standard choice. Neither SPZS-S1 nor SPZS-L1 is a secondary type.
Both grades are oil-soluble in Group I–III mineral and PAO base oils (>20% and >10% respectively); solubility in Group V ester stocks is not established, so confirm with our team if you formulate on esters. The two grades are fully comparable side by side in the Technical Specifications table at the top of this page — if you are unsure which tier fits your formulation, our technical team can advise on request.
Applications
This primary-alkyl ZDDP is used as the antiwear and antioxidant component in formulations targeting the categories below.
Engine oils (PCMO & heavy-duty diesel)
Protects the valve train, cam/follower and ring/liner contacts against wear while contributing oxidation control. SPZS-S1 covers general internal-combustion engine oils; SPZS-L1 suits high-grade turbocharged engine oils where sump temperatures run higher.
Antiwear hydraulic fluids
Provides vane- and piston-pump antiwear and oxidation stability. The hydrolytic stability of SPZS-L1 is valued in hydraulic systems that can pick up water — avoid ZDDP entirely in systems with silver-plated components (see the compatibility note below).
Industrial & gear lubricants
Delivers antiwear plus mild extreme-pressure protection in industrial oils and gear oils, usually combined with a sulfurized-olefin EP additive for the heaviest loads.
Lubricating greases & marine oils
Adds antiwear and EP performance to high-load and EP greases, and wear-plus-corrosion protection to marine engine oils alongside a high-TBN detergent package. SPZS-L1 is preferred for the high-temperature and moisture-exposed end of these uses.
Finished-oil OEM and industry approvals (API, ACEA, ILSAC, DIN and OEM bench sequences) are held by the fully formulated oil, not by an individual additive component.
Treat Rate & Phosphorus Budget
The technical data sheet gives the recommended treat rates below (identical for both grades). For ZDDP the figure that usually governs the dose in engine oils is phosphorus, because phosphorus is capped by modern specifications. The first-order phosphorus contribution to the finished oil is:
e.g. 1.0 wt% → ≈ 0.072% (720 ppm) · 3.0 wt% → ≈ 0.216% (2160 ppm)
| Application | Treat rate (TDS) |
|---|---|
| Industrial lubricants | 0.2–5.0 wt% |
| Engine oil | 1.0–3.0 wt% |
| Lubricating grease | 0.5–3.5 wt% |
Use the phosphorus calculation to keep within your specification: passenger-car oils targeting API SP or ILSAC GF-6/GF-7 cap phosphorus near 0.08% (800 ppm), and low-SAPS ACEA C1/C2 near 0.06%, because excess phosphorus can poison exhaust catalysts — so engine-oil treat sits at the lower end of the range, while off-highway, industrial and grease applications without a catalyst constraint can run higher. Where the phosphorus budget is tight, ZDDP is supplemented with ashless antiwear and organomolybdenum friction modifiers rather than simply raised.
The TDS treat ranges above are the manufacturer’s recommendations; the right level for your oil depends on the target specification, phosphorus/SAPS limit and the rest of the additive package. CheMost can provide formulation and treat-rate support on request.
Formulating With Primary-Alkyl ZDDP — Complementary Additives
ZDDP covers antiwear, antioxidancy and corrosion inhibition; a balanced package pairs it with additives that cover the rest of the performance envelope:
Detergents & TBN boosters
Overbased detergents neutralise acids and keep hot surfaces clean, and detergent surfaces help ZDDP build its antiwear film. Detergent and ZDDP levels are balanced together to manage the finished oil’s metal, ash and acid-base budget; with overbased detergents in water-exposed systems, confirm wet-filterability in screening.
Ashless dispersants
Dispersants suspend low-temperature soot and sludge while ZDDP handles wear; the detergent–dispersant–ZDDP balance is the core of every crankcase formulation.
Organomolybdenum friction modifiers
MoDTC/MoDTP friction modifiers work synergistically with ZDDP to reduce friction and wear, which lets formulators meet protection targets at a lower phosphorus level — useful where the SAPS budget is tight.
Extreme-pressure additives
For gear oils and greases, sulfurized-olefin EP additives are combined with ZDDP to carry the heaviest, highest-temperature contacts that ZDDP’s mild EP activity alone does not cover.
Documentation, Qualification & Regulatory Support
Standard documentation — Certificate of Analysis (COA, per shipment), Technical Data Sheet (TDS) and Safety Data Sheet (SDS, GHS/CLP) — is provided. The full TDS is available on request rather than as a public download. Additional support is available on request:
Regulatory documentation
REACH, TSCA and country-specific market-registration documentation support available on request.
Third-party inspection
SGS / Intertek / BV pre-shipment inspection can be arranged on request.
Custom grades & packaging
Custom grades and packaging — metal drum, IBC, ISO tank.
Formulation support
Treat-rate calculation and formulation guidance from our technical team.
Packaging & Supply
This primary-alkyl ZDDP is stocked and shipped worldwide, with a typical lead time of 1–15 days and a 36-month shelf life at ambient temperature (maximum storage 50°C; maximum blending temperature 70°C). Samples and quotations are answered within 12 hours.
Packaging
200 kg metal drum · 1000 kg IBC tank.
Minimum order
1 drum or 1 IBC — no minimum order value.
Incoterms
FOB · CIF · EXW, to suit your freight arrangement.
Loading ports
All major Chinese ports.
Frequently Asked Questions
What is zinc dialkyldithiophosphate (primary alkyl)?
It is a ZDDP antiwear additive in which the dithiophosphate ligands carry primary (C4/C8) alkyl groups. ZDDP is a multifunctional zinc-phosphorus compound that forms a protective antiwear film on metal under load and also acts as an antioxidant and corrosion inhibitor. The primary-alkyl class is the thermally and hydrolytically stable type, preferred for long-drain and high-temperature oils. CheMost offers a standard grade (SPZS-S1) and a long-chain grade (SPZS-L1).
What is the difference between SPZS-S1 and SPZS-L1?
Both are C4/C8 primary-alkyl ZDDP with the same phosphorus (7.2%) and zinc (8.55%), so they give the same antiwear chemistry. SPZS-S1 is the standard grade with good thermal stability, suited to internal-combustion engine oils and general industrial and grease use. SPZS-L1 is a long-chain grade with higher density and viscosity, better high-temperature stability and explicit hydrolytic stability — chosen for high-grade turbocharged engine oils, antiwear hydraulic oils and marine lubricants, and anywhere the oil runs hot or sees moisture.
How much ZDDP should I use, and why is phosphorus limited?
The TDS recommends 1.0–3.0 wt% in engine oils, 0.2–5.0 wt% in industrial lubricants and 0.5–3.5 wt% in greases. In engine oils the upper limit is set by phosphorus: at 7.2% P, a 1.0 wt% treat contributes about 720 ppm phosphorus. Modern specifications cap phosphorus near 0.08% (800 ppm) for API SP and ILSAC GF-6/GF-7, and near 0.06% for low-SAPS ACEA C1/C2, because excess phosphorus can poison exhaust catalysts. Calculate the phosphorus contribution before setting the dose, and confirm with our team for your package.
Is this primary ZDDP suitable for hydraulic oils and humid service?
Yes — primary-alkyl ZDDP is the hydrolytically stable class, and the long-chain SPZS-L1 grade is specifically described as not easily hydrolysed, which suits antiwear hydraulic fluids and other systems that can pick up water. The one exception is silver: ZDDP must not be used in hydraulic systems with silver-plated components (see below).
Is ZDDP compatible with every system?
ZDDP is compatible with mineral (Group I/II/III) and PAO base oils and most additive systems. However, it attacks silver and some copper alloys and can damage axial-piston pumps at sliding steel–copper interfaces, so silver-bearing systems require an ashless antiwear instead — a substitution, not a treat-rate change. It can also interact with overbased detergents in the presence of water to form filter-clogging by-products, so confirm compatibility in formulation screening.