Study on different types of car coolant used in Libyan market: additives dropout

: In this research, the effect of four types of coolants used in the local market, (namely Abrad, Freezetone, Algabl Green


Introduction
Liquid coolants like water and ethylene glycol are used into cooling system of internal combustion engines, and to improve their thermo physical properties metal oxides is added.Generally, a coolant is diluted by city water and well water.Since the quality of the waters is largely differ from place to place, a special care must be exercised when a corrosive water, which includes a lot of sulfate ion and chlorine ion, or a hard water, which includes a large of calcium and magnesium, is used [1,2].The quality of water in Japan is regarded as generally good, while water in Europe and Asia is hard and that in America the chance is high that water containing a high degree of sulfuric acid ion and chlorine ion is used for dilution, which can reflect on additives of coolant, and should be considered [3].
Additives for coolant are classified into the following four types.The first is called an anode type that becomes immobilized after forming an oxidation film or adsorption film on a metal surface.The second is called a cathode type that covers the metal surface with hydroxide deposited due to a chemical reaction or electrochemical reaction and thereby inhibits rust.The third is called an adsorption type that forms an anticorrosive film of a single molecule through combining with metal.The last is a filmforming type that forms insoluble polymer after reacting to copper [2,4].Engine was made of cast iron because of ease casting and nonappearance of appreciable shrinkage of volume, vibration damping wear resistance and machinability.Recently, aluminum used in automobiles to produce many engine parts such as piston and cylinder block to save weight [5,6].Engine coolant used in vehicle to minimize the degradation of nonmetals and prevent the corrosion of the metals in the cooling system.
Various forms of corrosion could occurred in cooling systems of engine, including uniform corrosion, galvanic corrosion, crevice corrosion, pitting corrosion, intergranular corrosion, erosion corrosion, and cavitations corrosion [7].An applicable treatment is used to give the cooling water the correct properties that prevents service problems.cooling water that has not had treatment can soon cause problems in the cooling system such as corrosion, sediment or hard particles.Corrosion protection oils (emulsion oils) are not recommended for the treatment of the cooling water.If instructions about the use of corrosion protection oils are not obeyed and coolant checks are not sufficient, then water / oil emulsion can occur.This can cause the cooling system to become clogged.Recently, there are a lot of coolant liquids in the Libyan market, some of which are manufactured locally and others are imported.Some of these liquids caused problems in car engines, such as corrosion and blockage of the engine or radiator caused by additives dropout.In this study, the percentage of additives dropout for four different coolants will be determined and the corrosion at core plug measured.

Experimental procedure
A consumed car engine cylinder block used in the present study.The chemical composition of the alloy was determined using FOUNDARY-MASTER Pro emission spark spectrometer.Table 1 shows the chemical composition of cylinder block alloy.

Table1: the chemical composition of cylinder block alloy
Twelve specimens are taken from cylinder block, three for each coolant type, which are cut into plates (35 mm×35 mm×12 mm) and then grounded and polished.Subsequently, they are immersed into engine coolants, which are Abrad, Freeztone, Algabl green, and Algabl Red for 72, 120, 216, , and 360 hr at room temperature as shown in Figure 1.The weight of additives dropout, and that precipitated on specimens is measured using a 1/10000 electronic balance.

Results and discussion
Figure 2 shows the surface morphologies of samples after 360 hr of immersion in coolants.As can be seen, the surfaces of the alloys extremely affected by the extension of immersion time, and the surface revealed significant additives dropout.It has been reported that many coolant additives like silicate and phosphate, which used as corrosion inhibitors in engine coolant, have limited solubility [8].That meant that if the antifreeze or additives got too concentrated in the coolant, then the excess phosphate and/or silicate would "dropout" of the coolant.These dropout problems caused premature water pump failures, radiator blockages, and heater core problems.Table 2 shows weight of samples before and after immersion on coolant liquids during 72, 120, 216 and 360 hrs.Fig. 3 shows three samples average of additives dropout quantity for four types of coolant.Indeed, considerable differences are noticed in the case of Algabl Green and Freeztone compared with Abrad and Algable Red, which were 0.00000478, 0.00000713033 g/hr/cm 2 for Algabl Green and Freeztone, respectively, while 0.00002.54304and 0.0000263792 g/hr/cm 2 for Abrad and Algable Red, respectively.

Fig. 3 : Effect of coolant type on additive dropout quantity
The additives can drop out of solution, causing deteriorating cooling system performance and wear in the coolant pump.This situation is greatly aggravated by poor coolant maintenance.In fact, more than 40% of diesel engine downtime is caused by cooling system failure.Even with good maintenance, conventional automotive or heavy duty coolant should be replaced every 2 or 3 years [9].Most cooling system water contains calcium and/or magnesium from drinking water supplies.Water that contains over 100 ppm of these minerals is considered "hard water".It is wonderful to drink, but these minerals can form scale in engine cooling systems.As the concentration of these minerals increases, so does the probability that you will have cooling system scale problems.The level of dissolved solids in coolant water is generally referred to as the "total hardness" reported in parts per million (ppm).Cooling system additives that contain anti-scale chemicals can allow the use of moderately hard water.It is best to use water that is at least as good as the recommended water quality listed in the ASTM standards [10].

Conclusion
In this study, the effects of engine coolant car on quantity of additive dropout were investigated.A significant notes observed using visual inspection, as the additives precipitate on the samples with different colors, However, these deposits were in different quantities with the different type of coolant used.Weight measurements showed that Al Gabal green was the lowest in dropout rate, which produced locally, compared with Abroad coolant type that import from overseas.In addition, the high dropout rate of Al Gable red compared with Al Gable green could be related to the dye type, as both coolants are produced by the same local company.

Table 2 :
Weight of samples before and after immersion in coolants