Article 3 Technical Information for WEBA Corp's Extended Life Antifreeze Additive Packages
As you may have already discovered, antifreeze technology has become significantly more complex since General Motors/Texaco introduced Dexcool® to the market in the mid 1990’s. Dexcool is a carboxylate-salt-based, extended-life antifreeze; Dexcool gave this technology, popularly called organic acid technology (OAT), a position of prominence in the U.S. market. Prior to the mid 1990’s, the U.S. market had been dominated by the so-called conventional antifreeze formulations, which are based on inorganic salts (sodium borate, sodium nitrate, sodium phosphate, sodium molybdate, sodium nitrite, etc.). Currently, conventional antifreeze formulations still have the largest part of the market, but OAT-type extended-life formulations have a major and growing share.
These two broad categories of antifreeze each have advantages and disadvantages relative to each other, and they have many similarities as well as differences. OAT, carboxylate-based antifreezes are touted as having longer potential service lives than conventional, inorganic salt inhibited antifreezes. This is based on the fact that carboxylate salts are not chemically consumed as they perform their function of inhibiting corrosion. Carboxylates protect metals from corrosion by forming a thin, molecular coating on them and thereby insulating them from any corrosive impurities that may form in the glycol/water base of the antifreeze. As long as the antifreeze volume in the cooling system is kept sufficiently high to coat all the metallic surfaces, and coolant is not lost due to leakage nor diluted by top-off with water or conventional antifreeze, it continues to be present in sufficient concentrations to function properly.
Conventional antifreeze formulations, however, usually contain a number of corrosion inhibitors that are consumed or transformed chemically as they perform their functions. For example, pH buffering compounds are used to maintain the pH in antifreeze in the range in which the individual inorganic salt inhibitors function properly. However, as exposure to heat and air causes the glycol base fluid to form glycolic acids, the pH buffers are consumed through reaction with these acids to form a neutral salt. Other inhibitors bond with the metal surfaces to protect them, but can be removed by impurities formed in or introduced to the antifreeze which convert them to other compounds. Other conventional inhibitors, such as silicates, combine with themselves and other compounds over time to form useless or harmful gelatinous materials.
The foregoing is the general theory. However, in reality, OAT formulations still contain some conventional corrosion inhibitors, such as tolytriazoles to protect “soft” metals (copper, solder, brass, etc.), which have shorter service lives than carboxylates. Carboxylates themselves can break down under certain conditions to form useless or even harmful chemicals, and they can react with conventional antifreezes (if mistakenly topped off with them, for example) to form compounds ineffective at corrosion inhibition.
Carboxylate-based OAT formulations have other disadvantages relative to conventional, inorganic salt based antifreezes. For example, they attack certain gasket materials. For this reason, Cummins engine has prohibited their use in its diesel engines. OAT-type antifreezes are also less viscous than conventional antifreezes, and as a result will leak out through smaller clearances than conventional antifreezes. On the other hand, the lower dissolved solids level in OAT-type antifreezes, associated with the lower viscosity range, make scale formation less of a problem than in the higher-dissolved-solids conventional formulations.
Within the category of OAT antifreezes there are two broad sub-categories: 1) Straight organic acid formulations; and 2) Hybrid, or mixed OAT/conventional formulations. One of the primary problems with straight OAT formulations, including Dexcool and Havoline Extended Life Antifreeze, is that they are not compatible with conventional antifreezes. The carboxylate salts used in straight OAT antifreeze react to some extent with some of the inorganic salts and caustics used in conventional antifreeze. The result of this interaction is the generation of cloudiness and precipitates. At best, if straight OAT antifreeze is topped off using a conventional antifreeze, the extended life rating of the OAT antifreeze (usually a service life of at least five years in an automotive application) is downgraded to the standard conventional service life of about two years. The warranties for most makes of automobiles that are factory filled with straight OAT antifreeze require all top-offs and refills to be made only with the same straight OAT antifreeze used in the factory fill.
Hybrid OAT antifreezes partially or totally eliminate the problem of straight OAT/conventional antifreeze compatibility problems. Hybrid OAT (HOAT) formulations contain significant concentrations of conventional antifreeze inhibitors/additives as well as an organic carboxylate salts. However, in this case the carboxylate salts are those that are totally compatible with the specific conventional antifreeze components used. WEBA Corp. has two broad-range HOAT additive packages (METALGUARD A40 and METALGUARD A60) that allow the antifreeze blender to make an OAT antifreeze that is totally compatible with every major national and regional brand of both conventional and OAT antifreezes, as confirmed by extensive compatibility and performance testing. Our customer uses METALGUARD A60 to make its extended life antifreeze.
The straight-OAT and Hybrid-OAT classifications each have two broad sub-categories: 1) automotive/diesel formulations; and 2) fully formulated, precharged, heavy-duty formulations. The first category meets ASTM specifications for automotive applications (ASTM D 3306) and heavy-duty diesel applications (ASTM D 4985). However, the latter requires an initial addition and subsequent periodic recharge of Supplemental Coolant Additives (SCA’s) to restore inhibitor levels after a specified number of operating hours, miles driven, etc. The second category, fully formulated, precharged, heavy-duty formulations, meets the fully-formulated, precharged ASTM standard (ASTM D 6210/6211). This means that these formulations meet the regular heavy-duty diesel specification (ASTM D 4985), plus they contain the initial charge of Supplemental Coolant Additive (SCA) and can function for a much longer period of time before any additional SCA must be added. A fully-formulated precharged straight-OAT or hybrid-OAT will usually meet the most demanding industry heavy-duty diesel specifications including Caterpillar EC-1 and the American Trucking Association’s Maintenance Council RP-329/330.Conventional, inorganic salt-type antifreezes can meet most of the same specifications as straight-OAT and hybrid- OAT formulations, depending upon which inorganic salts and caustics are included in their formulations. However, there are a few fundamental differences that should be highlighted at the outset:
Inhibitor System Primary Chemistry: Inorganic salts and caustic (sodium or potassium hydroxide) Carboxylate salts Carboxylate salts and inorganic salts pH Range: 10.0-11.0 8.3-9.5 9.0-10.5 Reserve Alkalinity: 10.0-18.0 3.0-6.0 4.0-10.0 Any specifications which have specific requirements in these areas may limit the type of antifreeze that can be used to meet them. However, specifications that allow broad ranges in these areas or do not state specific requirements in them, may allow the use of two or more of these types of antifreeze. Many specifications allow broad ranges in pH, reserve alkalinity and chemical composition, but require that they pass the performance tests in ASTM standards (i.e. Glassware Corrosion, Cavitation Erosion/Corrosion, Simulated Service, etc.). In some cases, the latter type of specifications can be met by any of the three categories of antifreeze in the preceding table.
Conventional antifreeze formulations cover a broad range of ingredient combinations. Some are based on a borate/nitrate primary inhibitor system; some are based on a molybdate/phosphate primary inhibitor system; some use a silicate aluminum protection system; some use proprietary non-silicate aluminum protection systems; some use tolytriazole to protect solder, copper and brass; some use sodium mercaptobenzotriazole to protect solder, copper and brass; some use both tolyriazole and sodium mercaptobenzotriazole; some use borate to buffer pH; some use phosphate to buffer pH; some use both borate and phosphate to buffer pH; some contain amines as vapor phase inhibitors, some don’t. The list of variations is extensive.
There are four primary classifications of conventional antifreeze: 1) Automotive, meeting ASTM D 3306; 2) Heavy-duty meeting ASTM D 4985; 3) Universal, meeting ASTM D 3306 and ASTM D 4985; and 4) Fully-formulated, precharged, heavy-duty, meeting ASTM D 6210/6211. The only significant difference between the automotive and heavy-duty ASTM standards, is that the heavy-duty standard requires a low silicate level (250 ppm maximum as silicon) while the automotive standard does not limit silicate. Almost all heavy-duty formulations are also universal formulations, meeting both ASTM D 3306 and ASTM D 4985. Fully-formulated, precharged, heavy-duty formulations must contain the initial charge of Supplemental Coolant Additive (SCA). This is spelled out in ASTM D 6210/6211 and the TMC of ATA RP 329/330 as a requirement for a minimum of 2400 ppm nitrite, or a minimum of 1560 ppm of combined nitrite and molybdate, with at least 600 ppm of each.
It should also be noted that, although the majority of products claiming to be extended life products are OAT-type antifreezes (either straight- OAT or hybrid- OAT) there are conventional formulations that make extended life claims also. Since silicate is the primary ingredient that limits conventional antifreeze formulation shelf and service life to a maximum of 2-3 years, extended life conventional antifreezes use non-silicate aluminum protection systems. ASTM is working on but has not yet issued an extended life antifreeze definition/standard. Which products truly qualify as extended life products will be sorted out when this standard is issued in 2004.
Now, two of the highest profile heavy-duty antifreeze specifications in the industry are Caterpillar EC-1 and RP 329/330 of the Technology and Maintenance Council of the American Trucking Association (TMC of ATA). Both can met by either hybrid- OAT antifreeze formulations or by selected fully-formulated, precharged antifreeze formulations. For example, let’s look closely at TMC of ATA RP 329. Some of its most important requirements for an antifreeze are as follows:
• A fully-formulated, precharged antifreeze containing the initial charge of supplemental coolant additive.
• No recharge of the inhibitor package until 300,000 miles of on-road use are logged.
• Addition of an extender/booster or supplemental coolant additive (SCA) at 300,000 miles to provide 300,000 more miles of on-road service.
• Antifreeze must have a non-silicate aluminum protection system and must contain no borates, phosphates or amines.
• Must be compatible with conventional coolants meeting ASTM D 4985.
• Must meet ASTM D 4985 and ASTM D 6210.WEBA Corp makes two additive packages that allows the antifreeze blender to meet these specification. Our customer uses both. They are:
• METALGUARD A81 – a conventional fully-formulated, precharged formulation using a non-silicate aluminum protection system based on a proprietary blend of triazoles and containing no borates, phosphates or amines.
• METALGUARD A60 – a hybrid- OAT-type, carboxylate-based, fully-formulated, precharged extended life additive system. It also contains no silicates, borates, phosphates or amines. Since it is a hybrid- OAT, it is compatible with conventional coolants meeting ASTM D 4985.The same evaluation can be done relative to Caterpillar EC-1. However, instead of a conventional antifreeze specification (like RP 329) that can be met with conventional or extended life antifreeze, with EC-1 we have an extended life specification that can be met with an extended life or conventional antifreeze.
I hope that this overview helps to explain some of the complexities of the antifreeze market that you alluded to in your email, and that it also gives you a clearer picture of the capabilities of the antifreeze that our customer makes with WEBA Corp.s additive packages. Feel free to call if you have any questions or need more information.
©2007 Richard Geib
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