Technical Specifications
| Property | Unit | Typical Value | Test Method |
|---|---|---|---|
| Appearance | Colorless or light yellow liquid | Visual | |
| Density at 20°C | kg/m³ | 1105 | ASTM D4052 |
| Viscosity at 100°C | mm²/s | 18.5 | ASTM D445 |
| pH | 6.5 | ASTM D1293 | |
| Flash point | °C | >180 | ASTM D93 |
| Sulphur | % | 14.82 | ASTM D4951 |
| Phosphorus | % | 7.45 | ASTM D4951 |
| Zinc | % | 9.22 | ASTM D4951 |
| Color | <0.5 | ASTM D1544 | |
| Moisture content | % | 0.03 | ASTM D95 |
| Mechanical impurities | % | 0.03 | ASTM D473 |
| Solubility (Group I–III / PAO) | >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 = C3 secondary + C4/C8 primary alkyl
A zinc cation coordinated by two O,O-dialkyl dithiophosphate ligands; in SPZS-M1 the alkyl groups are a mix of C3 secondary and C4/C8 primary.
What Is Zinc Dialkyldithiophosphate (Primary-Secondary Alkyl)?
CheMost SPZS-M1 is a primary-secondary alkyl zinc dialkyldithiophosphate (ZDDP) — a mixed-alcohol antiwear additive built, per its data sheet, on a mixture of C3 secondary alkyl groups and C4 + C8 primary alkyl groups. That deliberate primary-and-secondary blend is what defines the grade: the secondary component forms an antiwear film fast and at lower temperature, while the primary component restores thermal and hydrolytic stability and oil solubility.
Like all ZDDP it is multifunctional — antiwear agent, antioxidant and corrosion inhibitor in one molecule — but SPZS-M1 is tuned for a specific job. With rapid water separation (anti-emulsification), strong hydrolytic stability and high-temperature stability, it is positioned as the main antiwear agent for hydraulic oils and other industrial lubricants rather than as a crankcase additive.
It carries 7.45% phosphorus and 9.22% zinc — slightly higher metal and phosphorus than the pure-primary grades — at a viscosity of 18.5 mm²/s and a flash point above 180°C. For the purely primary-alkyl version of this chemistry, used mainly in engine oils, see the primary-alkyl ZDDP page.
How Primary-Secondary ZDDP Works
Fast antiwear tribofilm
Under boundary and mixed lubrication the ZDDP decomposes at the hot contact and builds a layered zinc/iron polyphosphate film that shears in place of the metal and self-renews from fresh additive in the oil. The C3 secondary component lowers the temperature at which that film forms, giving quick antiwear protection in pumps and industrial contacts.
Rapid water separation (demulsibility)
SPZS-M1’s stand-out property is rapid water separation and anti-emulsification — the additive lets a hydraulic or circulating oil shed water cleanly rather than forming stable emulsions, protecting filterability and pump life in systems that pick up moisture.
Hydrolytic & thermal stability
The C4/C8 primary content makes the molecule resistant to hydrolysis and stable at higher temperatures, so the antiwear chemistry survives in water-exposed and hot industrial service where a less stable additive would break down and form deposits.
Antioxidant & corrosion inhibition
As a peroxide decomposer, ZDDP slows the oxidation that thickens oil and forms acids; its dithiophosphate groups also passivate copper and bearing surfaces against acidic attack — extending oil life and protecting yellow-metal components.
Why a Primary-Secondary Alkyl Structure?
The two alkyl classes pull in opposite directions, and SPZS-M1 combines them on purpose. Secondary-alkyl ZDDP forms its protective film faster and at lower temperature and gives strong antiwear performance, but on its own it is less thermally and hydrolytically stable. Primary-alkyl ZDDP is the stable, long-lasting class but builds film more slowly. Blending a C3 secondary alcohol with C4 and C8 primary alcohols captures the fast, low-temperature antiwear of the secondary while the primary content restores the hydrolytic stability, high-temperature endurance and oil solubility an industrial fluid needs.
That balance is exactly what a hydraulic or industrial oil wants — quick antiwear protection at pump start-up plus durability and clean water separation over long service intervals. It is also why SPZS-M1 reads slightly higher in zinc (9.22%) and phosphorus (7.45%) and lower in flash point (>180°C) than the pure-primary grades: the shorter C3 secondary group raises metal content and is a little more volatile. If your application is an engine oil rather than a hydraulic or industrial oil, the pure primary-alkyl ZDDP is usually the better fit.
Applications
SPZS-M1 is used as the antiwear and antioxidant component in formulations targeting the categories below.
Antiwear hydraulic fluids
The primary use. Provides vane- and piston-pump antiwear with the demulsibility and hydrolytic stability hydraulic systems need, in formulations targeting industry standards such as DIN 51524 HLP and ISO HM hydraulic oils. Avoid in systems with silver-plated components (see the compatibility note below).
Industrial & circulating oils
Antiwear and oxidation protection for industrial gear, circulating and machine-tool oils where clean water separation and long-term stability matter.
Industrial oils requiring EP support
Supplies antiwear plus mild extreme-pressure activity; for the heaviest gear loads it is combined with a sulfurized-olefin EP additive.
Engine oils (secondary use)
The data sheet also lists engine-oil use; here the fast-forming secondary film contributes valve-train and cam antiwear, though the pure-primary grades are the usual choice for long-drain crankcase oils.
Finished-oil OEM and industry approvals (DIN, ISO, API, ACEA 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. The first-order phosphorus contribution to the finished oil is:
e.g. 0.5 wt% → ≈ 0.037% (370 ppm) · 1.0 wt% → ≈ 0.075% (745 ppm)
| Application | Treat rate (TDS) |
|---|---|
| Industrial lubricants | 0.2–5.0 wt% |
| Engine oil | 1.0–3.0 wt% |
In hydraulic and industrial oils the antiwear treat is usually modest — often around 0.2–0.7 wt% in line with general ZDDP practice — and is set by the antiwear performance target rather than by a phosphorus cap, since these fluids do not face the exhaust-catalyst phosphorus limits that constrain engine oils. Where the fluid is engine oil, keep the phosphorus contribution within the relevant specification.
The TDS treat ranges above are the manufacturer’s recommendations; the right level for your oil depends on the target specification and the rest of the additive package. CheMost can provide formulation and treat-rate support on request.
Formulating With SPZS-M1 — Complementary Additives
In a hydraulic or industrial oil, the antiwear ZDDP is balanced with additives that cover oxidation, corrosion, foaming and heavy-load protection:
Antioxidants
ZDDP is a peroxide decomposer; aminic and phenolic antioxidants are added for primary radical scavenging to extend oxidation life in long-service hydraulic and circulating oils.
Corrosion inhibitors & metal deactivators
Rust inhibitors and copper-passivating metal deactivators protect ferrous and yellow-metal surfaces and complement ZDDP’s own corrosion inhibition in water-exposed systems.
Foam inhibitors & defoamers
Hydraulic fluids must release air and shed water quickly; defoamers work alongside SPZS-M1’s demulsibility to keep the fluid free of stable foam and emulsions.
Extreme-pressure additives
For industrial gear and high-load circulating oils, sulfurized-olefin EP additives are combined with the ZDDP to carry the heaviest contacts that its 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
SPZS-M1 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 primary-secondary alkyl ZDDP?
It is a zinc dialkyldithiophosphate antiwear additive whose dithiophosphate ligands carry a deliberate mix of secondary and primary alkyl groups — in SPZS-M1, C3 secondary plus C4 and C8 primary. The secondary part gives fast, lower-temperature antiwear film formation; the primary part restores thermal and hydrolytic stability and oil solubility. The result is a balanced antiwear additive aimed at hydraulic and industrial oils.
How is SPZS-M1 different from the primary-alkyl grades?
The pure primary-alkyl grades (SPZS-S1/L1) are C4/C8 primary only and are aimed mainly at engine oils, with the highest thermal/hydrolytic stability. SPZS-M1 adds a C3 secondary component for faster, lower-temperature film formation and is built for hydraulic and industrial oils, with rapid water separation as a key property. It reads slightly higher in zinc (9.22%) and phosphorus (7.45%) and lower in flash point (>180°C).
Why is SPZS-M1 recommended for hydraulic oils?
Hydraulic fluids need fast antiwear protection for vane and piston pumps, plus the ability to shed water and resist hydrolysis over long service. SPZS-M1’s secondary-alkyl content gives the fast film, its primary-alkyl content gives the hydrolytic and thermal stability, and its rapid water separation (anti-emulsification) keeps the fluid clean — which is why the data sheet positions it as the main antiwear agent for hydraulic and industrial oils.
What treat rate should I use?
The TDS recommends 0.2–5.0 wt% in industrial lubricants and 1.0–3.0 wt% in engine oils. In hydraulic and industrial oils the antiwear treat is usually modest (often about 0.2–0.7 wt%) and set by the antiwear target. As a first approximation each 1.0 wt% contributes about 745 ppm phosphorus (treat % × 7.45 ÷ 100). Our technical team can help set the level for your fluid.
Is ZDDP compatible with every hydraulic system?
SPZS-M1 is compatible with mineral (Group I/II/III) and PAO base oils. However, ZDDP attacks silver and some copper alloys and can damage axial-piston pumps at sliding steel–copper interfaces, so systems with silver-plated components must use an ashless antiwear instead — a substitution, not a treat-rate change. Confirm compatibility in formulation screening, particularly where overbased detergents and water are also present.