MolaKule
Staff member
Boron Additives
By MolaKule
This white paper discusses the mechanics and chemistry of Boron Compounds as additives in Motor Oils, Gear Lubes, and Greases.
Organic Anti-Wear (AW) and Extreme Pressure (EP) additives act to reduce wear by depositing a surface film due to the mechanism of thermal decomposition. The AW and EP effectiveness is based on the degree of decomposition products in the zone of high friction and heat, thus suffer from thermal instability. Some of the older additives in this classification include: Zinc Dialkyl dithiophosphate or ZDDP, sulfur and phosphorous compounds (S-P), and chlorine and nitrogen (N) containing compounds.
There is a class of additives that deposit solid films by the action of “electrophoresis,” which will be explained later. Potassium Triborate (commercially in the form of
[K2O (B2O3)3], and Calcium Carbonate (CaCO3), fall into this class of additives that can form a rather tenacious coating on the sliding and shearing surfaces of machine parts. For example, the OilXtreme product usues a special CaCO3 additive in concentrate form. In some cases, the borates are in the form of “Overbased” Borated Sulphonates (OBS’), which of course contain boron, calcium, and sulfur. Some of the TBN’s of the OBS’ can be as high as 370 in the virgin form. These “Overbased” Borated Sulphonates are often added to large batches of oil to reduce the TBN. Some additive companies offer Borate esters which may contain some or all of the above components. For example, R.T Vanderbilt offers the ester flavor of the borates, while the Luboron Company offers their own borate-based products.
History:
In 1941, it was found that lead napthenates and free sulfurs (Pb-S) could raise the load carrying capabilities of gears and bearings at low speeds because they contributed a solid film of lead sulfate. They could not, however, resist the loading at high speeds, because the film rubbed off faster than the film could be re-deposited. Heat at high loads and speeds also melted away the solid films.
Later came the organic Sulfur-Phosphorus (S-P) additives which were found to outperform the Pb-S additives, because they formed films of iron sulfide and iron phosphate through thermal and oxidative decomposition. At high speeds, the films were replenished faster than they could be removed, which was an advantage over the Pb-S additives.
In 1967, tribological and chemical studies indicated that AW and EP films could be formed by lubricants containing borates. In 1976, J.H. Adams of the Chevron Research Company, patented a number of Borate Lubricants for Gear Lubricant applications. Since that time, a number of additive companies and internal oil company labs have produced many boron-type additives for gear, engine, and grease applications. Recently, Argonne National Lab’s Tribology Laboratory Section has done extensive studies with Boric Acid (H3BO3). Luboron’s products have arisen from these studies.
For gear lubes, the Potassium Triborate is in a finely dispersed form and usually mixed with soluble organic compounds for synergistic effects. While most AW or EP compounds form surface films by thermal decomposition, borate films form by electrostatic attraction, with the metal surface having the opposite charge of the boron particles, which promote a “static cling” effect. Once attracted, the borate films become solid films, and not chemically reacted films. Reduced temperatures of 6-30 C have been noted in gear boxes with these borate additives, and it has been reported that a 1.1% improvement in fuel economy has resulted, compared to the same gearboxes containing S-P additives.
For engine oils, there has been a need to reduce the poisoning of the exotic metals in catalytic converters from organic phosphorus compounds, usually due to the phosphorus in ZDDP. Whether this problem is real or perceived, this has led to the reduction of ZDDP and the increased use of non-phosphorus AW and EP additives such as MoTDC, SbDTC, and the Borates. In engine oils, the microparticulate borates are prepared by dissolving an alkali metal borate in the presence of a metal sulfonate and succinimde dispersant to form a micro-emulsion which is then added to a base oil, or as part of an additive package. When an oil uses this additive, an analysis of that oil will show both potassium and boron. The concentration of borate additives is in the range of 0.5% to 2% by weight. Any concentration less than 0.5%, or larger than 2%, shows up as increased wear in the 4-Ball Wear Testing machine. As you can see, additive chemistry is a meticulous balancing act, so as to preclude additive clash.
Many lubricating oils and greases now contain borates in various forms to reduce wear by the action of these solid borate films, which act as AW and EP additives. When used with the dithiocarbamate family of antimony’s and moly’s, corrosion and antioxidant resistant greases can be formulated as well to provide the same EP and AW qualities.
A side benefit of the borates in motor oils and gear lubricants is their action as mild detergents and as acid reducing agents. Their alkili chemistry helps to retain the oil's TBN, or Total Base Number as well.
[ May 19, 2003, 01:37 AM: Message edited by: MolaKule ]
By MolaKule
This white paper discusses the mechanics and chemistry of Boron Compounds as additives in Motor Oils, Gear Lubes, and Greases.
Organic Anti-Wear (AW) and Extreme Pressure (EP) additives act to reduce wear by depositing a surface film due to the mechanism of thermal decomposition. The AW and EP effectiveness is based on the degree of decomposition products in the zone of high friction and heat, thus suffer from thermal instability. Some of the older additives in this classification include: Zinc Dialkyl dithiophosphate or ZDDP, sulfur and phosphorous compounds (S-P), and chlorine and nitrogen (N) containing compounds.
There is a class of additives that deposit solid films by the action of “electrophoresis,” which will be explained later. Potassium Triborate (commercially in the form of
[K2O (B2O3)3], and Calcium Carbonate (CaCO3), fall into this class of additives that can form a rather tenacious coating on the sliding and shearing surfaces of machine parts. For example, the OilXtreme product usues a special CaCO3 additive in concentrate form. In some cases, the borates are in the form of “Overbased” Borated Sulphonates (OBS’), which of course contain boron, calcium, and sulfur. Some of the TBN’s of the OBS’ can be as high as 370 in the virgin form. These “Overbased” Borated Sulphonates are often added to large batches of oil to reduce the TBN. Some additive companies offer Borate esters which may contain some or all of the above components. For example, R.T Vanderbilt offers the ester flavor of the borates, while the Luboron Company offers their own borate-based products.
History:
In 1941, it was found that lead napthenates and free sulfurs (Pb-S) could raise the load carrying capabilities of gears and bearings at low speeds because they contributed a solid film of lead sulfate. They could not, however, resist the loading at high speeds, because the film rubbed off faster than the film could be re-deposited. Heat at high loads and speeds also melted away the solid films.
Later came the organic Sulfur-Phosphorus (S-P) additives which were found to outperform the Pb-S additives, because they formed films of iron sulfide and iron phosphate through thermal and oxidative decomposition. At high speeds, the films were replenished faster than they could be removed, which was an advantage over the Pb-S additives.
In 1967, tribological and chemical studies indicated that AW and EP films could be formed by lubricants containing borates. In 1976, J.H. Adams of the Chevron Research Company, patented a number of Borate Lubricants for Gear Lubricant applications. Since that time, a number of additive companies and internal oil company labs have produced many boron-type additives for gear, engine, and grease applications. Recently, Argonne National Lab’s Tribology Laboratory Section has done extensive studies with Boric Acid (H3BO3). Luboron’s products have arisen from these studies.
For gear lubes, the Potassium Triborate is in a finely dispersed form and usually mixed with soluble organic compounds for synergistic effects. While most AW or EP compounds form surface films by thermal decomposition, borate films form by electrostatic attraction, with the metal surface having the opposite charge of the boron particles, which promote a “static cling” effect. Once attracted, the borate films become solid films, and not chemically reacted films. Reduced temperatures of 6-30 C have been noted in gear boxes with these borate additives, and it has been reported that a 1.1% improvement in fuel economy has resulted, compared to the same gearboxes containing S-P additives.
For engine oils, there has been a need to reduce the poisoning of the exotic metals in catalytic converters from organic phosphorus compounds, usually due to the phosphorus in ZDDP. Whether this problem is real or perceived, this has led to the reduction of ZDDP and the increased use of non-phosphorus AW and EP additives such as MoTDC, SbDTC, and the Borates. In engine oils, the microparticulate borates are prepared by dissolving an alkali metal borate in the presence of a metal sulfonate and succinimde dispersant to form a micro-emulsion which is then added to a base oil, or as part of an additive package. When an oil uses this additive, an analysis of that oil will show both potassium and boron. The concentration of borate additives is in the range of 0.5% to 2% by weight. Any concentration less than 0.5%, or larger than 2%, shows up as increased wear in the 4-Ball Wear Testing machine. As you can see, additive chemistry is a meticulous balancing act, so as to preclude additive clash.
Many lubricating oils and greases now contain borates in various forms to reduce wear by the action of these solid borate films, which act as AW and EP additives. When used with the dithiocarbamate family of antimony’s and moly’s, corrosion and antioxidant resistant greases can be formulated as well to provide the same EP and AW qualities.
A side benefit of the borates in motor oils and gear lubricants is their action as mild detergents and as acid reducing agents. Their alkili chemistry helps to retain the oil's TBN, or Total Base Number as well.
[ May 19, 2003, 01:37 AM: Message edited by: MolaKule ]
