Formulation Design and Optimization of Hydraulic Oil Compound Additive
In the efficient operation of industrial hydraulic systems, the performance of hydraulic oil directly determines equipment lifespan and production efficiency. As the core carrier for enhancing the comprehensive performance of hydraulic oil, the formulation design and optimization level of hydraulic oil compound additives can be regarded as the "soul of oil performance". This article will start from the basic understanding of hydraulic oil compound additives, combine UNPChemicals' professional product system and measured data, systematically dissect the core principles of formulation design, the logic of additive selection, optimization methods, and practical cases, providing both professional and implementable technical references for potential customers such as hydraulic oil production enterprises and equipment operation and maintenance teams, while demonstrating UNPChemicals' technical strength in the field of compound additive formulation research and development.
1. What is a hydraulic oil compound additive?
Hydraulic oil compound additives are not single additives, but rather a combination of functional additives composed of various single-function agents such as anti-wear agents, antioxidants, rust inhibitors, anti-foaming agents, metal deactivators, and anti-emulsifiers, formulated through scientific proportioning and synergistic compounding. Their core mission is to endow base oils (such as mineral oils, synthetic oils, or CTL base oils) with "full operating condition adaptability" - for example, protecting hydraulic pumps from wear through anti-wear components, delaying oil aging through antioxidant components, inhibiting corrosion of metal components through rust inhibitor components, and ultimately ensuring the stable operation of hydraulic systems under complex environments such as high and low temperatures, high loads, and humidity.
As a globally leading professional hydraulic oil additive supplier , UNPChemicals has been deeply involved in this field for over a decade, always adhering to the philosophy of "making addition simple", and has built a product matrix covering different environmental protection standards and different load requirements. Its star products include:
High-Zinc Anti-Wear Hydraulic Oil Compound UNP AH502A: With a zinc content of 7.2% (wt), it is renowned for its excellent anti-wear performance and high load-carrying capacity. It can be formulated into high-performance anti-wear hydraulic oils that meet international standards such as GB11118.1-2011 and DIN51524, and is suitable for industrial hydraulic systems with stringent requirements for wear protection;
Low-Zinc Hydraulic Oil Compound UNP AH502B: While maintaining the basic anti-wear performance, it controls the zinc content at a lower level, taking into account both environmental compliance and equipment compatibility, and is suitable for scenarios with certain restrictions on heavy metal content;
Zinc-Free Hydraulic Oil Compound UNP AH502C: Completely free of zinc components, compliant with strict environmental regulations such as the European Union's RoHS, and specifically designed for hydraulic systems with extremely high environmental requirements, such as those in electronics and food machinery.
It is worth emphasizing that formulation design is the "decisive factor" for the performance of hydraulic oil additives. For the same combination of single additives, improper proportioning not only fails to exert synergistic effects but may also lead to performance conflicts - for example, excessive anti-foaming agent may cause a decline in air release performance, and a single high-dose anti-wear agent may sacrifice anti-rust effectiveness. Taking UNP AH502A as an example, its formulation precisely regulates the proportions of sulfur (13.5%), phosphorus (6.5%), and zinc (7.2%) to construct a "zinc-sulfur-phosphorus" synergistic anti-wear system. After adding 0.6% to 46# Group I base oil, the PB value (maximum non-seizure load) reaches 90 kg, and the PD value (sintering load) reaches 126 kg, far exceeding the industry's basic standard (the PB value of ordinary additives is usually 60-80 kg), which is a direct manifestation of the value of scientific formulation design.
2. Basic Principles of Formula Design
The formulation design of hydraulic oil compound additives is not a "stacking of functions", but rather a dynamic balance and collaborative optimization centered around the five core properties of "anti-wear, anti-oxidation, anti-rust, anti-foam, and anti-emulsification". Excessive enhancement of any single property may lead to an imbalance in overall performance. The following are the three core balance principles and UNPChemicals' practical solutions:
Balance between anti-wear performance and environmental compliance
Anti-wear is the core requirement of hydraulic oil. Although traditional anti-wear agents (such as ZDDP, zinc dialkyldithiophosphate) can achieve anti-wear by forming sulfide and phosphate protective films on the metal surface, excessive zinc content may not comply with environmental regulations. Formulation design needs to find a balance between "anti-wear effectiveness" and "zinc content limits".
The solution of UNP AH502A is highly representative: it adopts the "high zinc + high-efficiency synergy" strategy. Although its zinc content of 7.2% (wt) is higher than that of low-zinc/no-zinc products, through the precise ratio of sulfur and phosphorus components (sulfur 13.5%, phosphorus 6.5%), it achieves a synergy effect of "1+1+1>3" in anti-wear performance - in the four-ball test, the PB value reaches 90 kg and the PD value reaches 126 kg, far exceeding that of ordinary complex agents with the same zinc content (usually with a PB value of around 80 kg). Meanwhile, by optimizing the molecular structure, it has excellent hydrolytic stability (copper strip weight loss is only 0.02 mg, total acidity of the water layer is 0.03 mgKOH/g, SH/T 0301 standard), avoiding zinc salt precipitation that causes environmental pollution, and taking into account both anti-wear performance and environmental protection bottom line.
Balance between oxidation resistance and low-temperature fluidity
Antioxidants (such as amines and phenols) can effectively delay the high-temperature oxidation of oil, but some high-dose antioxidants (such as hindered phenols) may increase the low-temperature viscosity of oil, affecting system start-up in winter or low-temperature environments. Formulation design needs to balance antioxidant life and low-temperature fluidity through "type selection + dosage control".
The formulation innovation of UNP AH502A lies in the selection of an "amine-phenol composite antioxidant system", which not only retains the long-term high-temperature effectiveness of amine antioxidants but also enhances low-temperature activity through phenolic antioxidants while controlling the total addition amount (no additional antioxidant supplementation required). Measured data shows that the rotating oxygen nitrogen test (150°C) result of its formulated oil reaches 432 minutes (SH/T 0193 standard), more than 1.5 times that of ordinary compound additives, indicating a significant extension of antioxidant life; meanwhile, the kinematic viscosity at 40°C is 175 mm²/s (GB/T 265 standard), and after 72 hours of low-temperature storage at 0°C, there is no stratification or precipitation, with low-temperature fluidity meeting the usage requirements for environments above -10°C, perfectly resolving the "antioxidation-low temperature" contradiction.
Balance between rust prevention performance and anti-emulsification performance
Rust inhibitors (such as carboxylic acid soaps and benzotriazole) achieve rust prevention by forming an adsorption film on the metal surface, but some polar rust inhibitors may reduce the anti-emulsification performance of the oil, making it difficult to separate water and thus accelerating corrosion instead. Formulation design requires the selection of rust inhibitors with "low polarity + high adsorption" and their synergy with anti-emulsifiers.
The anti-rust and anti-emulsification synergistic design of UNP AH502A is exemplary: it adopts a "carboxylate-metal deactivator composite anti-rust system" with moderate polarity, which can not only form a dense anti-rust film by combining carboxyl groups with metal ions (no rust in both distilled water and artificial seawater in the 24h liquid-phase rust test, GB/T 11143 standard), but also not damage the oil-water separation ability of the anti-emulsifier. Actual measurements show that the anti-emulsification performance (40-37-3, 54°C) of its formulated oil is only 7 minutes (GB/T 7305 standard, with the index requirement ≤30 minutes), far superior to the industry average. Even when 2% water enters the system, it can still quickly achieve oil-water separation, avoiding the adverse interaction between the anti-rust agent and water.
3. Selection and Function of Additives
The formulation design of hydraulic oil compound additives essentially involves "precise selection + synergistic combination" of various additives. The functional characteristics and applicable scenarios of different additives vary significantly. The following details the selection logic and mechanism of action of core additives in combination with the formulation composition of UNP AH502A:
Anti-wear agent: The "wear-resistant shield" of hydraulic systems
Anti-wear agents are the core component of hydraulic oil additives, and their function is to form a protective film on the metal contact surfaces of hydraulic pumps, valves, etc., preventing wear caused by direct metal friction. The selection criteria must meet the three major requirements of "high load-carrying capacity, low wear rate, and good compatibility with base oil".
UNP AH502A selectsZDDP (Zinc Dialkyldithiophosphate) as the primary anti-wear agent, combined with a small amount of phosphate ester auxiliary anti-wear agent:
Advantages of ZDDP: Through chemical adsorption, it forms a "zinc sulfide - zinc phosphate" composite protective film on the metal surface. The film has a moderate hardness (HV 300 - 400), which can withstand high loads (PD value 126 kg) without scratching the metal surface due to excessive hardness. Meanwhile, ZDDP also has certain antioxidant properties, which can help delay the aging of oil products;
Function of Auxiliary Anti-wear Agent: Under high temperature and high pressure (such as the local temperature of a hydraulic pump reaching 120°C), phosphate additives can quickly replenish the protective film, preventing "secondary wear" after the ZDDP film layer breaks. Actual measurements show that the failure level of the gear machine test for UNP AH502A formulated oil is not less than 10 (SH/T 0306 standard), and the wear amount under 1200 r/min operation is far lower than the industry standard, fully verifying the reliability of the anti-wear system.
Antioxidants: The "Extenders" of Oil Life
During long-term high-temperature operation (system oil temperature often reaches 60-80°C), the base oil molecules in hydraulic oil are prone to oxidation, generating polar substances such as carboxylic acids, aldehydes, and ketones, which leads to an increase in the acid value and viscosity of the oil, ultimately forming sludge. The core function of antioxidants is to capture oxidation free radicals and terminate the oxidation chain reaction.
UNP AH502A uses a compound antioxidant system of octylated phenyl-α-naphthylamine (amine) + hindered phenol (phenol):
Amine antioxidants: Excellent high-temperature oxidation resistance, effectively inhibiting the oxidative degradation of oil at temperatures above 100°C, and serving as the core of the compound additive's "long-lasting oxidation resistance".
Phenolic antioxidants : High activity at low temperatures, capable of inhibiting slow oxidation during the normal temperature storage stage (such as before the oil is used) to prevent premature increase in acid value;
Synergy effect: After the combination of the two, the antioxidant efficiency is much higher than that of a single antioxidant - the Rotating Oxygen Nitrogen Test (150°C) reaches 432 minutes, and the acid value change rate in the Thermal Stability Test (135°C, 168h) is only 0.90% (GB/T 4945 standard), indicating that the oil can still remain stable under long-term high temperature, significantly extending the oil change interval.
Rust Inhibitor and Metal Passivator: The "Rust Prevention Barrier" for Metal Components
Metal components such as steel and copper in hydraulic systems are prone to corrosion when exposed to moisture and oxygen, which not only affects the precision of the components but may also generate rust particles that clog the filter. The combination of rust inhibitors and metal passivators can form a dual protection of "physical adsorption + chemical passivation".
The anti-rust system of UNP AH502A consists of disodium sebacate (carboxylate anti-rust agent) + benzotriazole (copper passivator) :
Carboxylate rust inhibitors: The carboxyl group (-COOH) in the molecule combines with the hydroxyl group (-OH) on the metal surface to form a dense physical adsorption film, which isolates moisture and oxygen from contacting the metal. The liquid-phase rust test (24h) shows no rust, verifying its protective effect on steel components;
Copper Passivator: Benzotriazole (BTA) can form a stable chelate film with copper ions, inhibiting the dissolution and corrosion of copper components. The copper strip corrosion test (100°C, 3h) is only Grade 1a (GB/T 5096 standard), and the weight loss of the copper rod is only 0.1mg/200ml (thermal stability test data), preventing oil discoloration and system contamination caused by the dissolution of copper ions.
Antifoam and Demulsifier: The "Scavengers" for System Stability
Hydraulic oil is prone to mix with air during the circulation process, forming foam, which leads to system pressure fluctuations and increased noise; if water enters, it may also form an emulsion, accelerating oil hydrolysis and additive failure. The functions of anti-foaming agents and anti-emulsifying agents are to solve the problems of "foam" and "water" respectively.
The formulation of UNP AH502A integrates polyether modified silicone antifoam + nonionic demulsifier :
Antifoam agent: Achieves excellent antifoaming effect without additional supplementation —— In the foam characteristics test (ASTM D892), the foam volume in Procedure I (24°C) is 20/0 ml/ml, and in Procedure II (93.5°C) is 10/0 ml/ml. The foam dissipates quickly, preventing the formation of stable foam that could affect system operation;
Demulsifier : The non-ionic structure can reduce the oil-water interfacial tension, accelerate oil-water separation, with demulsibility (40-37-3, 54°C) only 7 minutes. Even when 2% moisture enters the system, it can still maintain good filtration performance (filtration value 144 with 2% water, close to 122 when anhydrous), preventing sludge formation and filter clogging caused by emulsions.
4. Methods and Practices of Formula Optimization
The formulation optimization of hydraulic oil compound additives is not a "trial-and-error adjustment" but a scientific process based on "performance target - experimental verification - data feedback - iterative optimization". Taking the formulation optimization of UNP AH502A as an example, UNPChemicals has developed a complete methodology from laboratory-scale trials to industrial applications, specifically including the following four key steps:
Define performance objectives: Set "quantitative indicators" based on application scenarios
The first step in formula optimization is to set quantifiable performance indicators based on the target application scenarios (such as high-load hydraulic systems, low-temperature environments, and environmental protection requirements) to avoid "general optimization." Taking the optimization of UNP AH502A as an example, its initial target was set as follows:
Anti-wear performance: PB value ≥ 85 kg, PD value ≥ 120 kg (meeting the requirements of high-load hydraulic pumps);
Oxidation resistance: Rotary oxygen nitrogen test (150°C) ≥ 400 min (extends oil change interval to over 12 months);
Anti-emulsification performance: ≤10 min (meeting the water separation requirements in humid environments);
Environmental protection requirements: Comply with GB11118.1-2011, hydrolysis stability meets the standard (to avoid zinc salt pollution).
These goals are not set out of thin air, but are based on UNPChemicals' research on customer needs. For example, 80% of industrial hydraulic customers have reported that "insufficient anti-wear performance leading to premature pump failure" and "frequent oil changes increasing costs" are the main pain points. Therefore, anti-wear and anti-oxidation performance have been listed as the core optimization directions.
Single-agent screening and synergy testing: Eliminate "performance conflicts" and strengthen "synergy effect"
After clarifying the objectives, it is necessary to conduct single-agent screening tests to determine the optimal type and dosage range of each functional single agent, while verifying the synergy between different single agents to avoid conflicts. Taking the optimization of the anti-wear system of UNP AH502A as an example:
Single-agent screening: The performance of three anti-wear agents, ZDDP, phosphate ester, and sulfurized olefin, was tested separately. It was found that ZDDP exhibited the best performance in terms of PB value (88 kg) and compatibility with base oil (no precipitation), so it was determined as the main anti-wear agent;
Synergistic Experiment: By testing the combined effects of ZDDP with different auxiliary anti-wear agents, it was found that when ZDDP was compounded with phosphate ester (mass ratio 5:1), the PB value increased to 90 kg, and the PD value reached 126 kg, a 10% increase compared to single ZDDP, indicating the existence of a synergy effect; if combined with sulfurized olefin, the PB value was only 85 kg, and slight precipitation occurred, so it was determined as a "conflicting combination" and excluded.
Similarly, in the optimization of the antioxidant system, by comparing the results of the rotating oxygen nitrogen test of "amine single agent", "phenolic single agent", and "amine-phenol composite", it was found that the antioxidant life of the composite system (mass ratio 3:1) reached 432 min, far higher than that of the single agents (amine 320 min, phenolic 280 min), and finally the composite antioxidant scheme was determined.
Orthogonal Experiment and Parameter Optimization: Precise Identification of the "Optimal Formula"
After the single-agent screening is completed, it is necessary to optimize the dosages of key single agents through orthogonal experiments (Orthogonal Experiment) with multiple factors and multiple levels to find the formulation combination with the optimal performance. Taking the optimization of the core parameters of UNP AH502A as an example, three key factors, namely "ZDDP dosage (A), amine-phenol antioxidant dosage (B), and rust inhibitor dosage (C)", are selected, with each factor having 3 levels (e.g., A1 = 6%, A2 = 7%, A3 = 8%). An L9 (3⁴) orthogonal table is designed to test the PB value, oxidation life, and rust prevention performance of different combinations. Finally, through range analysis, it is concluded that:
Key factors affecting PB value: A (ZDDP dosage) > C (rust inhibitor dosage) > B (antioxidant dosage), with optimal levels being A2 (7%), B2 (2%), and C1 (1%);
Key factors affecting oxidation life: B (antioxidant dosage) > A (ZDDP dosage) > C (rust inhibitor dosage), with the optimal levels being A2 (7%), B3 (3%), and C1 (1%);
After comprehensive consideration, the final formulation was determined to be A2, B2.5 (2.5%), C1, which not only ensures the PB value reaches 90 kg, but also extends the oxidation life to 432 min, while maintaining the anti-rust performance without loss, achieving "optimal multi-performance".
Industrialization verification and adjustment: Ensure that "laboratory performance" translates into "practical application"
After the laboratory optimization is completed, it is necessary to verify the performance of the formulation under actual working conditions through industrial pilot testing (100 kg scale) and on-site customer trials to avoid differences between laboratory and industrialization. The industrial verification process for UNP AH502A is as follows:
Pilot Verification : At a scale of 100 kg, using 46# Class I base oil and adding 0.6% UNP AH502A, the key performance was tested: PB value 89 kg (close to 90 kg in the laboratory), anti-emulsification 8 min (7 min in the laboratory), with stable performance and no batch differences;
Customer trial: A construction machinery factory used the pilot product in 50 hydraulic excavators. After 6 months of continuous operation, the acid value of the oil increased from 0.8 mgKOH/g to 1.2 mgKOH/g (while that of ordinary compound additives increased to 1.8 mgKOH/g), the wear of the hydraulic pump decreased by 30%, and there was no filter clogging. The customer feedback indicated that "the oil change interval was extended to 12 months, and the equipment failure rate decreased by 25%", which verified the industrial applicability of the formula.
In response to the issue of "slightly slow winter start" reported by customers in individual low-temperature regions during the trial, UNPChemicals further adjusted the type of antifoaming agent (replacing it with a polyether type with better low-temperature fluidity), reducing the viscosity at 0°C by 10%, resolving the low-temperature start issue, and completing the final optimization.
5. Conclusion
The formulation design and optimization of hydraulic oil compound additives is a systematic project "oriented by customer needs, supported by scientific experiments, and centered on the synergy effect". By disassembling the formulation case of UNPChemicals UNP AH502A, three key success factors can be summarized:
Precise positioning of requirements is the prerequisite: Formulation design must first identify the core pain points of the application scenario (such as high load, environmental protection, low temperature), set quantitative performance targets, and avoid "blind optimization". UNP AH502A precisely determined the core direction of "zinc-sulfur-phosphorus anti-wear system + amine-phenol antioxidant system" based on the customer's requirements for "high anti-wear + long-lasting antioxidant";
Maximizing the synergy effect is the key: No matter how excellent the performance of a single additive is, if it conflicts with other components, it cannot form a high-quality formulation. Through extensive synergy tests, UNP AH502A eliminates conflicting combinations (such as ZDDP + sulfurized olefin) and strengthens synergistic combinations (such as ZDDP + phosphate ester, amine + phenol), enabling the overall performance to far exceed the sum of single components;
Data drive is the guarantee: From single-dose screening to orthogonal experiments, and then to industrial verification, every step must be based on measured data to avoid "empiricism". During the optimization process of UNP AH502A, a total of over 200 experiments were conducted, obtaining over 1,000 sets of data, ultimately achieving excellent performance with a PB value of 90 kg, oxidation life of 432 min, and anti-emulsification property of 7 min, with traceable data and reproducible results.
The Price of Hydraulic Oil Additives Package
The price of Hydraulic Oil Additives Package varies depending on factors such as brand, specification, composition, and sales channels. If you are interested in Hydraulic Oil Additives Package, please feel free to contact us.
Supplier of Hydraulic Oil Additives Package
UNPChemicals is a professional supplier of high-quality and effective Hydraulic Oil Additives Package. We offer several remarkable products, namely High zinc hydraulic oil additives UNP AH502A,Low Zinc Hydraulic Oil Additives UNP AH502B,Zinc-free Hydraulic Oil Additives UNP AH502C,etc.
High zinc hydraulic oil additives UNP AH502A are a type of chemical additive used in hydraulic oils that contain high levels of zinc dialkyldithiophosphate (ZDDP). ZDDP is a well-known anti-wear agent that also provides antioxidant, anti-corrosion, and anti-foam properties. The zinc in these additives plays a crucial role in forming a protective film on metal surfaces within the hydraulic system, thereby reducing wear and extending the life of the system components.
Low Zinc Hydraulic Oil Additives UNP AH502B are a class of advanced lubricant additives designed to enhance the performance of hydraulic oils with reduced zinc content.These additives are formulated to provide a balance of anti-wear,extreme pressure,and antioxidant properties,making them suitable for modern hydraulic systems that demand high performance with lower environmental impact.
Zinc-free Hydraulic Oil Additives UNP AH502C are a new class of environmentally friendly lubricant additives designed for hydraulic systems.These additives are formulated to provide the same level of performance as traditional zinc-containing additives but without the heavy metal content,reducing the environmental impact of hydraulic fluids.
Professional Lubricant Additive Manufacturer
UNPChemicals,aka Luoyang Pacific United Petrochemical Co., Ltd., focuses on the application and development of special lubricating grease additives such as MODTC, MODTP, molybdenum amide, thiadiazole metal deactivators, and phosphate esters. With nearly 30 products in seven series, including extreme pressure anti-wear additives and special grease additives, it is a global manufacturer of special lubricating grease additives and a national high-tech enterprise with great influence and leading role in the industry. If you are looking for Lubricant Additive or technical information, feel free to contact UNPChemicals.