Technical Specifications
| Property | Unit | Typical Value | Test Method |
|---|---|---|---|
| Appearance | Colorless or light yellow liquid | ||
| Density at 20°C | kg/m³ | 1145 | ASTM D4052 |
| Viscosity at 100°C | mm²/s | 17.0 | ASTM D445 |
| pH | 5.9 | ASTM D1293 | |
| Flash point | °C | >170 | ASTM D93 |
| Sulphur | % | 17.35 | ASTM D4951 |
| Phosphorus | % | 8.91 | ASTM D4951 |
| Zinc | % | 9.89 | ASTM D4951 |
| Color | - | <0.5 | ASTM D1544 |
| Moisture content | % | 0.03 | ASTM D95 |
| Mechanical impurities | % | 0.03 | ASTM D473 |
| Solubility in Mineral Group I, II and III | >20% |
* Typical values from batch production. Batch-specific COA available on request.
Technical content reviewed by the CheMost additives team · Specifications last reviewed
Application Data
Compatible Base Oils
Molecular Structure
Molecular structure · zinc dithiophosphate
Zn[(RO)₂PS₂]₂ — R = secondary alkyl
Two O,O-dialkyl dithiophosphate ligands coordinated to a single zinc centre. In SPZS-SE2 each alkyl group is bonded through a secondary carbon, and that is what drives the faster film build.
What Is Zinc Dialkyldithiophosphate (Secondary Alkyl)?
CheMost supplies a secondary-alkyl zinc dialkyldithiophosphate (ZDDP) — the fast-acting end of the zinc-phosphorus antiwear additive family. Every alkyl group sits on a secondary carbon, and that single structural choice is what separates this grade from the primary and mixed-alkyl types: it decomposes more readily at the rubbing contact, so the protective film builds sooner and at lower oil temperature.
SPZS-SE2 is a bi-structured secondary-alkyl grade, and it carries the highest element loading of the three ZDDP families we stock: 8.91% phosphorus, 9.89% zinc and 17.35% sulphur by ASTM D4951. High zinc is the headline number, but the figure that changes a formulation is the ratio — at 8.91% P this grade delivers a given phosphorus target on less additive mass, and brings less zinc and less sulphur along with it, than any other ZDDP on this site.
It is an almost colourless liquid, with a colour below 0.5 by ASTM D1544, a density of 1145 kg/m³ and a viscosity of 17.0 mm²/s at 100 °C. It dissolves above 20% in Group I, II and III mineral stocks.
We hold no solubility figure for PAO or ester stocks, so raise that with our technical team before you formulate on synthetics.
How Secondary-Alkyl ZDDP Works
Faster antiwear film build
Under boundary lubrication the additive decomposes at the hot asperity contact and lays down a glassy zinc and iron polyphosphate layer that takes the shear the metal would otherwise take. Because a secondary alkyl group leaves more easily than a primary one, the published antiwear ranking across the class runs secondary > primary > aryl — the film forms sooner and at lower sump temperature. That is the practical case for this grade: cold-start and break-in wear, where a primary grade is still warming up to its working temperature.
Strongest peroxide-decomposing action
The same reactivity drives the oxidation side of the job. ZDDP destroys the hydroperoxides that thicken oil and generate acid, and the measured antioxidant ranking follows the same order as the antiwear ranking — secondary above primary above aryl. In a package that already runs a phenolic or aminic antioxidant, a secondary grade lets you carry that load on less supplementary chemistry.
The stability trade-off, and how this grade answers it
Classically the price of secondary-alkyl reactivity is durability: across the class, thermal stability runs aryl > primary > secondary, and hydrolytic stability runs primary > secondary > aryl. SPZS-SE2 is bi-structured for precisely that reason — it holds up at higher temperature and is not easily hydrolysed, which is what makes a secondary grade usable in high-grade engine oils rather than only in short-drain or break-in service.
Bearing and yellow-metal protection
The dithiophosphate groups adsorb onto bearing alloys and form a passivating layer against the acidic by-products of combustion and oil ageing. The one hard exclusion is silver: no ZDDP belongs in a system with silver-plated components, and that is a substitution to an ashless antiwear chemistry, not a treat-rate adjustment.
Choosing Between Secondary, Primary and Mixed-Alkyl ZDDP
All three are zinc dialkyldithiophosphates and all three build the same kind of film. What differs is how fast that film forms, how long the additive survives, and — the part most selection guides skip — how much zinc and sulphur you have to accept to buy a given amount of phosphorus. The right way to compare them is at equal phosphorus, not at equal treat rate:
| Grade | Alkyl type | P / Zn / S | Dose for 800 ppm P | Zn and S it brings with it |
|---|---|---|---|---|
| SPZS-SE2 | Secondary | 8.91 / 9.89 / 17.35% | 0.90 wt% | 888 ppm Zn · 1558 ppm S |
| SPZS-M1 | Primary-secondary | 7.45 / 9.22 / 14.82% | 1.07 wt% | 990 ppm Zn · 1591 ppm S |
| SPZS-S1 | Primary | 7.20 / 8.55 / 15.50% | 1.11 wt% | 950 ppm Zn · 1722 ppm S |
Read the table right-to-left. At the same 800 ppm phosphorus, this grade needs about 0.90 wt% where the primary grade needs 1.11 wt% — roughly a fifth less additive mass, and about a tenth less zinc and sulphur carried into the finished oil.
In a low-SAPS formulation those two right-hand columns are the whole argument, because ash and sulphur are capped independently of phosphorus.
Where each one wins. Choose SPZS-SE2 when film build speed, low-temperature wear or a tight ash and sulphur budget is the constraint. Choose the primary grade when maximum thermal and hydrolytic durability in a long-drain or moisture-exposed oil outranks reaction speed. The mixed primary-secondary grade sits between the two and is the usual answer when you want some of the secondary response without moving the whole antiwear system. All three are compared side by side against their own specifications on the linked pages; our technical team can review your target and say which tier fits.
Applications
CheMost positions this grade for high-grade engine oils. That is the application it is built and sold for, and we do not extend it to hydraulic, gear or grease service the way the primary-alkyl grades are extended — the reactivity that makes a secondary ZDDP good at fast film build is the same property that has to be re-qualified in every other environment.
High-grade engine oils
The antiwear and antioxidant component for valve train, cam/follower and ring/liner protection in engine oils where the phosphorus, ash and sulphur budgets are already tight. The high phosphorus assay is what makes it fit: it reaches the specification’s phosphorus target on the smallest additive charge of the three families.
Cold-start and low-temperature wear
The class-level reason to pick a secondary grade is that its film establishes at lower temperature than a primary grade’s. Where your wear result is being lost in warm-up rather than at full operating temperature, this is the structural change worth screening — as a substitution for, or a partial replacement of, the incumbent primary ZDDP.
Formulation and qualification trials
Base-oil group, the detergent and dispersant balance, the element caps of the target specification and the intended bench programme all move the answer. Confirm wear performance, oxidation response, seal and elastomer behaviour, and storage stability in the finished blend — a component assay is a starting point for a trial matrix, never a substitute for one.
Finished-oil OEM and industry approvals (API, ACEA, ILSAC, and OEM bench sequences) are held by the fully formulated and qualified oil, never by an individual additive component.
Treat Rate and Phosphorus Budget
We publish no recommended treat window for this grade, and we will not lend you one from a sibling product. That is deliberate: for a modern engine oil the dose is not set by the additive at all — it is set by the phosphorus, ash and sulphur ceilings of the specification you are targeting. What you need from us is the conversion, and the assay is precise enough to give it to you exactly:
ppm Zn = T × 989
ppm S = T × 1735
T is the treat level expressed in weight percent, so a one-percent charge means T = 1.
How to read it. Work backwards from the ceiling, not forwards from a dose. Every current ILSAC GF-6 and GF-7 category caps phosphorus at 0.08 mass%, or 800 ppm, and each also sets a phosphorus floor of 0.06 mass%, or 600 ppm — the limit that catches formulators out. If this grade is your only phosphorus source, those two limits pin it into a window of roughly 0.67 to 0.90 wt%.
The newer categories add a sulphated ash cap of 0.9 mass%, and at the top of that window the zinc in this additive contributes about 0.22 mass% ash — 888 ppm scaled by the ZnSO₄ conversion factor of 2.47 that sits behind ASTM D874. That leaves roughly three quarters of the ash budget for your detergent system.
Sulphur is the limit people forget. At 17.35% this grade is sulphur-rich, and sulphur is capped separately from phosphorus. Run it at 0.90 wt% and it alone contributes about 0.156 mass% sulphur.
Against a mid-SAPS target that is comfortable: the sulphur cap of ACEA C2 is 0.3%, so there is room left over.
Against low-SAPS it is tight. ACEA C4 holds sulphur to 0.2%, and this additive alone would take roughly 78% of that. Check the sulphur column before the phosphorus one whenever the target is low-SAPS.
Where the phosphorus budget will not stretch, the answer is not more ZDDP. It is to pair a smaller ZDDP charge with ashless antiwear chemistry and an organomolybdenum friction modifier, which is the standard route to hitting a wear target under a hard element cap.
The figures above are arithmetic from this grade’s published assay and from public specification limits — they are a calculation method, not a recommended dose. What is right for a given oil follows from its category, its element ceilings, the rest of the additive system and the bench programme behind it. CheMost provides treat-rate calculation and formulation review on request.
Formulating With Secondary-Alkyl ZDDP — Complementary Additives
This grade covers antiwear, antioxidancy and corrosion inhibition. A balanced engine-oil package pairs it with the chemistry that covers the rest of the envelope — and with a reactive secondary ZDDP, two of those pairings need more attention than usual:
Ashless dispersants
The pairing to screen first. Basic nitrogen from a succinimide dispersant complexes with ZDDP, and above a critical dispersant level that complex measurably suppresses antiwear film formation. Fix the dispersant-to-ZDDP ratio by test rather than by assumption, especially when you have deliberately chosen a reactive secondary grade to gain film speed.
Detergents and TBN boosters
Overbased detergents carry the acid-neutralisation reserve and the piston-deposit control, and their surfaces assist film build. They also spend the same sulphated-ash budget this additive draws on, so set the two together against the category’s ash cap — and confirm wet filterability where an overbased detergent and moisture can meet.
Antioxidants
Because a secondary ZDDP is the strongest peroxide decomposer of the class, the supplementary phenolic and aminic load can often be trimmed rather than simply added to. Establish the balance by oxidation bench testing; the saving is real but it is formulation-specific.
Organomolybdenum friction modifiers
MoDTC and MoDTP work synergistically with ZDDP on friction and wear, which lets you hit a protection target at a lower phosphorus level. That is the lever to reach for when the specification’s phosphorus floor and its ash cap are squeezing you from both sides.
Documentation, Qualification and Regulatory Support
A Certificate of Analysis (COA) ships with every consignment. The Safety Data Sheet (SDS, GHS/CLP) and the full product specification are issued to enquirers directly, not posted as a public download. Further support:
Regulatory documentation
REACH, TSCA and country-specific market-registration paperwork prepared on request.
Third-party inspection
Independent pre-shipment inspection arranged on request.
Custom grades and packaging
Custom grades and packaging — metal drum, IBC, ISO tank.
Formulation support
Element-budget and treat-rate calculation, and formulation review, from our technical team.
Packaging, Storage and Supply
Shipped worldwide from all major Chinese ports, with a 36-month shelf life at ambient temperature. Store dry, clean and well ventilated below 50 °C, and keep blending below 70 °C — that ceiling is well under the >170 °C flash point, and staying beneath it protects the additive rather than the operator. 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.
Handling
Maximum storage 50 °C · maximum blending 70 °C · consult the SDS before handling.
Frequently Asked Questions
What is secondary alkyl ZDDP, and how does it differ from primary?
It is a zinc dialkyldithiophosphate in which the alkyl groups are attached through secondary carbons. A secondary alkyl group leaves more easily than a primary one, so the additive decomposes sooner at the rubbing contact: across the class, antiwear action and peroxide-decomposing action both rank secondary above primary above aryl, while thermal and hydrolytic durability rank the other way round. SPZS-SE2 is a bi-structured secondary grade designed to keep the reactivity while holding up at higher temperature and resisting hydrolysis.
How much should I use?
We publish no treat window for this grade, and borrowing one from a primary-alkyl product would be wrong. Set the dose from your specification’s element ceilings instead, using the conversions below, in which T is the treat level in weight percent:
ppm P = T × 891
ppm Zn = T × 989
ppm S = T × 1735
For an oil capped at 800 ppm phosphorus with a 600 ppm floor, that puts this grade in a window of roughly 0.67 to 0.90 wt% if it is your only phosphorus source. Confirm the final level by testing.
Why does the high phosphorus content matter?
At 8.91% phosphorus it reaches a given phosphorus target on less additive mass than the mixed grade at 7.45% or the primary grade at 7.20%. Zinc and sulphur ride along in fixed proportion, so less mass means less ash and less sulphur for the same wear chemistry.
Hold phosphorus at 800 ppm and this grade brings about 888 ppm zinc and 1558 ppm sulphur with it, against 950 and 1722 respectively for the primary grade. Under a low-SAPS cap, that gap is what decides whether the formulation closes.
Is it suitable for low-SAPS engine oils?
It is the most element-efficient of our three ZDDP families, which helps. Run the sulphur arithmetic before you commit, though: at 0.90 wt% it contributes about 0.156 mass% sulphur.
That fits inside the mid-SAPS sulphur cap of ACEA C2, which is 0.3%.
It is far tighter against ACEA C4, whose low-SAPS ceiling of 0.2% would be roughly 78% spent by this additive alone. For the strictest categories, plan on a reduced charge supported by ashless antiwear and organomolybdenum chemistry.
Which base oils does it dissolve in?
Above 20% in Group I, II and III mineral stocks. We hold no solubility figure for this grade in PAO or in Group V esters — if your base stock is synthetic, raise it with our technical team while the trial is still being designed.
Is it compatible with every system?
No, and the exclusions matter more than the compatibilities. ZDDP corrodes silver and can damage sliding steel–copper interfaces in axial-piston pumps; a silver-bearing system needs ashless antiwear chemistry, which is a change of additive rather than a change of dose. Two further interactions are worth screening: overbased detergent plus water can throw filter-clogging by-products, and succinimide dispersant above a critical level complexes the ZDDP and blunts its film.
How is it packaged, stored and shipped?
200 kg metal drums and 1000 kg IBC tanks, from all major Chinese ports on FOB, CIF or EXW terms, with a minimum order of one drum or one tank.
Shelf life is 36 months at ambient temperature. Store dry, clean and well ventilated below 50 °C, and blend below 70 °C. Consult the SDS before handling.