58 journal of mineral, metal and material engineering

58 Journal of Mineral, Metal and Material Engineering, 2019, 5, 58-72

E-ISSN: 2414-2115/19 © 2019 Scientific Array

Study on Corrosion Inhibitors of Eco - Friendly Radiator Coolants

A. Rajendiran1,2,*, Elmi Elias2,3, Kashinath Sutar1,4, S.R. Paranjpe1, K. Krishnasamy2 and D. Ganguli1

1R&D Centre, Bharat Petroleum Corporation Ltd., Mumbai- 400 015, India 2Department of Chemistry, Annamalai University, Chidambaram – 608002, India 3Higher Colleges of Technology, Abu Dhabi Men’s College, Abu Dhabi, UAE 4Department of Chemistry, Shri Jagdishprasad Jhabarmal Tibrewala University, Jhunjhunu, India

Abstract: Radiator coolant is a heat transfer fluid designed to remove excess heat from combustion engine. Conventional coolant contains amines, phosphates, borates and silicates as corrosion inhibitors. This corrosion inhibitor used against corrosion. Due to environmental policies, some chemicals are restricted to use in coolants. There is a need to develop eco- friendly chemical based coolants. Developing coolants without these chemicals is arduous. Author attempted to develop eco- friendly coolant and tested as per international standards. The loss of weight of all metal coupons due to corrosion are very low and hence it enhances the life of engine in automotive vehicles. Also this formulation saves energy due to less corrosion of metals used in radiators.

Keywords: Inhibitors, antifreeze, corrosion, hardness, radiator, freezing.

1. INTRODUCTION

Worldwide nearly 2000 million liters of Antifreeze are sold every year. Engine coolant usage continues to increase on a worldwide basis as the overall vehicle population becomes larger. Many off-highway vehicles and stationary equipment facilities also uses engine coolant. Engine typically converts only one third of the energy derived through the combustion of fuel into work that moves the vehicle. The other two- thirds is converted into heat, of which one third goes out with the exhaust. This leaves the remaining third in the engine block, necessitating the need for a coolant to adsorb this heat, transport it to the radiator and dissipate it into the environment. Through the removal of this heat by the coolant fluid, the engine is able to operate in an efficient.

The importance of Antifreeze /Coolants serves three key functions: The first is to draw heat away from hot engine parts to prevent over heating during use; the second is to prevent freezing of the coolant when the vehicle is unused in cold climates; the third is to inhibit corrosion of the metal components of the cooling system and engine block.

Antifreeze is a water-based liquid coolant used in gasoline and diesel engines. Compounds are added to the water to reduce the freezing point below the lowest temperature and also to inhibit corrosion in cooling

*Address correspondence to this author at the Department of Chemistry, Annamalai University, Chidambaram – 608002, India; Tel: +919869448815; E-mail: [email protected]

systems which contain different metals used in manufacturing of engines blocks and thermostats (aluminum, cast iron, copper, lead solder, etc.) [1]. The novel synthesized inorganic compound (Sodium cobalt phosphite) was evaluated by M.A. Deyeb, et al. [2] and reported as corrosion inhibitor in coolants for Aluminum based engine block. Molybdate compounds were identified as corrosion inhibitor for ferrous and non- ferrous metals. As molybdate compounds are very low toxicity, it meets environmental aspects and reported by M.S. Vukasovich, et al. [3]. Global competition and increasing environmental awareness are creating markets for products that reduce impact of the environment. Engine coolants must inhibit corrosion of cooling system which made by metals. These include steel, cast iron, copper, brass, lead solders and cast aluminum.

This paper discusses about the comparison of the performance of various corrosion inhibitors and their compatibility problems with different hardness water. Also, it describes about the environmental issues. Ashvin K. Dewan, et al. [4] studied and found that corrosion rate at the metal is strongly influenced by the diffusion of protonated amine. Extended life of coolant depends upon the presence of corrosion inhibitors. The inhibitor contains one or combination of nitrites, phosphates, silicates and or organic acid technology (OAT). Sebacic acid, ethyl hexanoic acid or benzoic acid have been corrosive certain vehicle seals and gaskets studied and reported by Szilagyi [5]. No single inhibitors shielding all ferrous and non-ferrous metals and aggregate protection needs several inhibitors [6].

Study on Corrosion Inhibitors of Eco - Friendly Radiator Coolants Journal of Mineral, Metal and Material Engineering, 2019, Vol. 5 59

Yukasovich et al. [7] reported that aluminum heat transfer corrosion was inhibited by silicate and poorly inhibited by borate and phosphate. Further, copper was inhibited by molybdate and phosphate and poorly by nitrate, silicate and benzoate.

Sodium molybdate protects ferrous metals, aluminum heat transfer, and aluminum water pump cavitation erosion-corrosion, solder corrosion and pitting of radiator aluminum with phosphate or silicate as an engine coolant corrosion inhibitor [8-9].

European Automotive Original Equipment Manufacturer (OEMs) are not recommending phosphates based coolants, but United States Automotive OEMs are accepting phosphate based coolants whereas they are not recommending Amine based coolant [10]. Silicates found to be the best corrosion inhibitor, but tends to deplete fast in cooling system. Similarly, Japanese Automotive OEMs are accepting Amine based and Phosphate based coolants but they are not recommending silicate based coolants. In view of this, each OEM has its own strategy on recommendation of coolant. Almost 60 % of coolants marketed in India were based on inorganic chemical based corrosion inhibitors. About 25% of coolants marketed in India were hybrid based (organic and inorganic) corrosion inhibitor.

Generally sodium salt of decandioic acid found to be an effective corrosion inhibitor. Poly-carboxylic acid protect metal parts by forming thin layer which protect metals. It demonstrates adsorption behavior on metal surfaces. Also, organic acid inhibitors deplete very slowly [11-12].

Cast iron has been the traditional material for cylinder blocks, heads and liners. But it replaced by lighter aluminium alloys that has better thermal conductivity. Copper/brass radiators are being replaced by aluminium radiators. However heavy- duty diesel engine systems uses more traditional material. Steel, cast iron, copper alloys are used in cooling pump impellers and thermostats [13-14]. Corrosion inhibitors are required in a balanced formulation to protect aluminium, steel, cast iron, copper, solder and brass. Most of the commercially available corrosion inhibitors are protected only ferrous metals but it did not protect Aluminium based metals studied by Dungall, et al. [15]. The combination of dissimilar metals operating in the cooling system at high temperatures leads to severe corrosion in heat-transfer corrosion reported by W. Zhou, et al. [16].

Amine and amine phosphates are good protection for Aluminium and cast iron. Triazoles are protecting for copper and brass corrosion [17-18]. Benzoate is inhibitor for cast iron and solder [19]. Protection of ferrous metals using nitrite is very effective whereas “nitrate” is effective in Aluminium protection. Generally” Borax” is very good corrosion inhibitor for metal coupons used in Glassware test [20]. “Sebacates” are used for protection of ferrous and iron corrosion [21]. W.L. Falke [22] studied and reported that corrosion experiments were conducted on commercially available antifreeze based on phosphorus, borate and silicate based and concluded that weight loss due to corrosion on particularly solders.

Generally amines, borates and phosphates were used in conventional coolants and both inhibitors were good corrosion inhibitors of ferrous and Aluminium metal. However, these chemicals were not allowed to use in coolants by some of the OEMs. In this study, we have developed coolants free from amine, borate, phosphates and silicate and studied various corrosion tests.

The purpose of coolants is to remove excess heat evolved from engine and control metal temperature in safe limits. Water is good heat transfer fluid, but it has shortcoming of freezing point which is at 0°C also boils at 100°C. Glycols were added with water to overcome with this problem [23].

2. EXPERIMENT DETAILS

In this study different corrosion inhibitors dissolved in Mono Ethylene Glycol (MEG) which is used as main solvent. Also, MEG is the best antifreeze solvent and it shows for good flow characteristics even at low temperatures. All chemicals are sourced from Spectrochem, Sigma-Aldrich and e Merck with 99.5 to 99.9% purity.

The Metal test pieces shall meet the dimension (50mm x 25mmx3mm for Aluminum and other metals (50mmx25mmx 1.6mm) respective specification.

• Aluminium (Copper 3%to 4.5; Silicon 4.0 to 6.0%; Magnesium 0.25% max; Iron 0.80% max; Nickel 0.30% max; Aluminium balance %)

• Cast Iron (Carbon 3.0 to 3.3%; Silicon 1.8 to 2.2%; Manganese 0.6 to 0.9%; Sulphur 0.15% max; Phosphorus 0.12% max)

60 Journal of Mineral, Metal and Material Engineering, 2019, Vol. 5 Rajendiran et al.

• Steel (Carbon 0.12% max; Manganese 0.5% max; Sulphur 0.045% max; Phosphorus 0.040% max)

• Brass (Copper 64.0 to 68%; Lead 0.07max; Iron 0.05max)

• Solder (Lead and Tin alloy having 29 to 31 %)

• Copper (Copper having 99.9% minimum)

2.1. Ethylene Glycol

Water is used as a coolant because of its high specific heat capacity, water can absorb large amounts of excess heat without much increase in temperature. It absorbs a lot of thermal energy and releases it reasonably quickly. The high specific heat of water provides for efficient thermal transitions of the radiator. Water is a pretty effective coolant, but if it freezes, it can expand enough to burst the rigid enclosure of an engine or electronic. Antifreeze was developed to overcome the shortcomings of water as a heat transfer fluid. Ethylene glycol is widely used to lower the freezing point of water and to raise its boiling point to enable the coolant to be used over a wider range of temperatures. Water used for engine cooling is a mixture of water and an antifreeze with additives, of which the recommended is ethylene-glycol Ethylene glycol and other such antifreezes tend to corrode the metals from which the internal combustion engines are made under the conditions of elevated temperature and aeration. Therefore, it has been necessary to add corrosion inhibitor compositions to the antifreeze solutions to lessen the corrosive effect of the solutions.

2.2. Different Formulation

Ten coolants namely A, B, C, D, E, F, G, H, I and J were formulated with Ethylene Glycols and different corrosion inhibitors and copper passivators. The formulation details of coolant A, B, C, D, E, F, G, H, I and J were given in Tables 1 & 2.

2.3. Physio-Chemical Tests

The physio- chemical properties were tested as per ASTM D 4985/ASTM D 3306 specification and JIS K 2234:1994. All the tests were carried out of all coolants as per JIS K 2234:1994. The physio- chemical tests were given in Tables 3 to 8.

2.3.1. Density by Hydrometer Method (ASTM D 1122)

This method covers the determination of density of concentrate coolant by hydrometer method. Took the sample into glass cylinder so carefully that no air bubbles present and brought the sample to room temperature, insert hydrometer allow hydrometer to float. When the hydrometer had come to rest, floating freely without touching inner wall of glass cylinder, read hydrometer reading nearest 0.005 also read the thermometer reading nearest 0.5°C and record.

2.3.2. Water Content by Karl Fischer Method (ASTM D 1123)

This method is to determine water contained in the sample unreacted with Karl Fischer reagent. Titrated proper amount of methyl alcohol with Karl Fischer reagent to the end point. The reagents include alcohol,

Table 1: Formulation Details

Components Sample A Sample B Sample C Sample D Sample E

Mono carboxylic acid (Type I), %

◊ ◊ ◊ ◊

Mono carboxylic acid (Type II), %

● ● ●

Dicarboxylic acid, % ● ● ●

Metallic borate □ □

Amines © © ©

Benzoate ● ● ● ●

Nitrite,% ○ ○ ○ ○ ○

Molybdate, % ● ● ● ● ●

Azole, % ● ● ●

Caustic, % ● ● ● ●

Remarks Borate based Amine and borate based Amine and Borate based HOAT based HOAT based


Table 2: Formulation Details

Components Sample F Sample G Sample H Sample I Sample J

Mono carboxylic acid (Type I), %

◊ ◊ ◊

Mono carboxylic acid (Type II), %

● ●

Mono carboxylic acid (Type III), % β β

Mono carboxylic acid (Type IV), % Ѱ Ѱ

Alkyl benzoic acid,% ⃝ ⃝ ⃝

Dicarboxylic acid (Type I), %

● ● ●

Dicarboxylic acid (Type II), %

& &

Dicarboxylic acid (Type III), %

ẟ ẟ ẟ ẟ

Salts of Tricarboxylic acid

α α

Azole derivative √ √ √ √

Benzoate ●

Molybdate, % ● ● ●

Azole, % ●

Caustic, % ● ● ● ● ●

Remarks HOAT based HOAT based HOAT based HOAT based HOAT based

Table 3: Tests as Per ASTM D 3306 Specification

Sl.no Tests/ Samples (ASTM) Sample A Sample B Sample C Sample D Sample E

1 Density@20°C (D1122) 1.120 1.121 1.119 1.120 1.120

2 Boiling point, °C (D 1120) 166 165 168 170 168

3 Water content, % by mass (D 1123) 3.5 2.6 2.5 2.7 3.0

4 pH of 30%(v/v) aqueous soln. (D 1287) 8.28 8.30 8.22 8.25 8.24

5 Freezing point, °C (D 1177) i) 50% aqueous soln. ii) 30% aqueous soln.

Minus 36 Minus 15

Minus 36 Minus 12

Minus 33 Minus 15

Minus 36 Minus 15

Minus 36 Minus 15

Table 4: Tests as Per ASTM D 3306 Specification

Sl.no Tests/ Samples (ASTM) Sample F Sample G Sample H Sample I Sample J

1 Density@20°C (D1122) 1.122 1.120 1.120 1.121 1.119

2 Boiling point, °C (D 1120) 168 167 169 172 170

3 Water content,% by mass(D 1123) 2.5 2.7 2.6 2.6 2.8

4 pH of 30%(v/v)aqueous soln. (D 1287) 8.27 8.28 8.25 8.24 8.28

5 Freezing point, °C (D 1177) i)50% aqueous soln. ii)30% aqueous soln.

Minus 36 Minus 12

Minus 38 Minus 12

Minus 33 Minus 15

Minus 36 Minus 15

Minus 36 Minus 15


Table 5: Glassware Corrosion Test –ASTM D1384

Metals Specification, as per JIS K 2234,

mg/cm2 Sample A Sample B Sample C Sample D Sample E

Aluminium +/-0.15 -0.20 -0.22 -0.12 -0.18 -0.06

Cast iron +/-0.15 +0.11 -0.18 -0.13 -0.09 -0.05

Steel +/-0.15 +0.12 +0.03 +0.11 +0.08 -0.06

Brass +/-0.15 -0.22 -0.05 -0.20 -0.10 -0.05

Solder +/-0.30 +0.35 -0.27 -0.29 -0.21 -0.09

Copper +/-0.15 +0.20 -0.05 -0.18 -0.08 -0.07

Visual observation

Clear and no precipitate

No precipitate Lot of precipitate Lot of precipitate No precipitate appears

Clear no precipitate

Table 6: Glassware Corrosion Test –ASTM D1384


mg/cm2 Sample F Sample G Sample H Sample I Sample J

Aluminium +/-0.15 -0.03 -0.14 -0.02 -0.05 -0.10

Cast iron +/-0.15 +13.84 -0.03 -0.02 -0.04 -0.07

Steel +/-0.15 - 0.11 -2.97 -0.38 -0.06 -0.01

Brass +/-0.15 -0.76 -0.83 -0.21 -0.03 -0.04

Solder +/-0.30 -2.39 -0.02 -1.27 -0.07 -0.01

Copper +/-0.15 -0.04 -0.04 -0.14 -0.03 -0.04

Visual observation


Precipitate appears

precipitate appears

Lot of precipitate No precipitate appears

Clear no precipitate

Table 7: Circulation Corrosion Test –ASTM D2570


mg/cm2 Sample A Sample B Sample C Sample D Sample E

Aluminium +/-0.30 -0.55 -0.31 -0.80 -0.22 -0.11

Cast iron +/-0.30 +0.19 -0.22 -0.38 -0.14 -0.10

Steel +/-0.30 +0.10 +0.08 +0.40 +0.12 -0.09

Brass +/-0.30 -1.60 -0.13 -0.22 -0.21 -0.08

Solder +/-0.60 +0.60 -0.57 -0.62 -0.63 -0.12

Copper +/-0.30 +1.50 -0.08 -0.05 -0.20 -0.13

Visual observation


Precipitate appears

Precipitate and discolouration


No precipitate appears


SO2, a base and I2. Add the weighed sample to the titration vessel. Begin adding reagent from the burette while stirring. When the endpoint is reached, the electrode will detect no change in current upon addition

of more reagent. By knowing how much titrant was added, the water content can be calculated. Normally, the K-F instrument does the calculations and reports the results as “% water” or “ppm water.”


2.3.3. Determination of pH of Coolant (ASTM D 1287)

A sample, as received or after dilution with a specified volume of distilled water, is placed in beaker and the pH measured with pH meter. After calibrating pH meter, the electrode was washed and immediately pH of the sample was measured and reported.

2.3.4. Freezing Point (ASTM D 1177)

The method involves the determination of the time-temperature curve prior to freezing and the determination of the horizontal or flattened portion of the freezing curve. The freezing point is taken as intersection of projections of the cooling curve and the freezing curve. The test sample was prepared as per the method. 75 to 100 ml Sample was taken in the cooling tube and attach a stirrer with thermometer through a cork. The cooling tube was kept in cooling medium and continue for stirring. The recording of the temperature every minute and when it approaches 5°C above the expected freezing temperature was done. Nearing the expected freezing temperature, measure to nearest 0.1°C, every 15secs, and prepared the freezing temperature curve. From the curve, calculated the freezing point at which the curve becomes parallel and reported as freezing point.

2.3.5. Boiling Point (ASTM D 1120)

This method covers the determination of the equilibrium boiling point of engine coolants that are miscible with water. The equilibrium boiling point indicates the average temperature of the boiling fluid at the end of reflux period. Took 60ml of the sample with three pieces of boiling tips in two neck round bottom glass flask and inserted the condenser in one neck and insert thermometer into another neck. Sample was heated for 10 minutes for reflux and adjusted the

heating so that 1 to 5 drops per second during reflux. Heating was regulated 1 to 2 drops per second for 5 minutes. During this time, read the temperature to nearest 0.5°C and recorded as equilibrium reflux boing point.

2.3.6. Glassware Metal Corrosion (ASTM D1384)

The chemical composition of metal specimens are given in test method. In this method, specimens of metals typical of those present in automotive cooling systems are totally immersed in the test antifreeze solution with aeration for 336 hours at 88° C. The corrosion inhibition properties of the test solution are evaluated on the basis of the weight changes incurred by the specimens. Each test is run in duplicate, and the average weight change is determined for each metal. The composition of corrosion test pieces should meet as per specification. Coolant sample was diluted with 30% of 700 ppm hardness water. 750ml of diluted solution was taken into glass beaker immersed one set of weighed test pieces and insert thermometer and ventilating tube as per Figure 1. Similarly make triplicate test. Kept all the assembled beakers to the heating device and maintained the temperature at 88° C for 336 hours. After completion of the test, wash the each test piece as per method and record the mass difference.

2.3.7. Circulation Corrosion Property / Simulated Service Corrosion Testing of Engine Coolants (ASTM D 2570)

The chemical composition of metal specimens are given in test method. This test equipment is manufactured in accordance to ASTM D 2570. It consists of heating bath, circulating pump, and radiator assembly for evaluating the effects of engine coolant on metal specimens by circulation continuously for

Table 8: Circulation Corrosion Test –ASTM D2570


mg/cm2 Sample F Sample G Sample H Sample I Sample J

Aluminium +/-0.30 -0.59 -0.37 -0.75 -0.11 -0.11

Cast iron +/-0.30 +8.19 -0.22 -0.38 -0.19 -0.10

Steel +/-0.30 -0.30 -1.78 -0.49 -0.12 -0.09

Brass +/-0.30 -1.80 -0.19 -0.42 -0.21 -0.08

Solder +/-0.60 +1.60 -0.59 -0.69 -0.13 -0.13

Copper +/-0.30 +1.30 -0.18 -0.19 -0.15 -0.10

Visual observation


Precipitate appears

Precipitate appears


No precipitate appears



specified period under controlled laboratory conditions as per Figure 2. It is a floor mounted bench. The temperature of the coolant sample is maintained at 88°C (190°F), flow rate is about 60 LPM and the test is continued for about 6 weeks (1000 hours). This test method evaluates the effect of a circulating engine coolant on metal test specimens and automotive cooling system components under controlled, essentially isothermal laboratory conditions. Assembled 3 sets of weighed test pieces immersed in 7 litres of diluted coolant solution (concentrate coolant diluted with 30% 700ppm hardness water) as per method.

Maintained the temperature of the solution at 88°C, flow rate was maintained at 60 ml minute. This test was carried out for 1000hours. After completion of 1000 hours, weighed the test pieces as per method and the observation of colour of the solution, pH value of the solution, reserve alkalinity was recorded.

2.3.8. Hard Water Stability (ASTM D 7437 / ASTM D 1126)

This test method provides information on the stability of an engine coolant diluted with synthetic hard water at elevated temperatures. This test method

Figure 1: Glassware corrosion tester.

Figure 2: Circulation corrosion tester.


provides a laboratory method to test the sensitivity of the engine coolant to hard water. 60 ml of concentrate coolant was taken in beaker and mixed with 140 ml of 700 ppm hardness water. This beaker was kept on hot plate for 8 hours at 88°C. After the test, kept for cooling for 16 hours, took 100 ml sample and measured the precipitate after centrifuge.

3. RESULTS AND DISCUSSION

3.1. Physio-Chemical Properties

All coolant samples (A, B, C, D, E, F, G, H, I and J) were carried out all physio -chemical tests like hard water stability, Boiling point, Freezing point, Glassware metal corrosion property and Circulation corrosion property and the results were exhibited.

3.2. Corrosion Inhibitors

Salts of mono, di and tri carboxylic acid found to be an effective corrosion inhibitors for all metals particularly aluminium and yellow metals. Also it was observed that Butanic, Hexanoic and Decanoic acids shown better protection of Aluminium. The phosphate buffer gives better liner pitting protection. Also, it is good for solder corrosion and it protects solder. Phthalic acid, Isophthalic acid and Terephthalic acid prevents metal corrosion. Phthalic acid used in the range of 0.2 to 0.5% and Terephthalic acid used in 0.5 to 1.0%. Thiazoles used for yellow metal corrosion protection and it is used in the range of 0.2 to 0.5%. Tolytriazole is good corrosion inhibitor for aluminium and yellow metals compare to sodium tolytriazole. It has got negative impact that it’s foaming. We need to add antifoaming agents which will increase corrosion of other metals. Nitrite is particularly effective for protection of ferrous metals like steel, cast iron but has got serious effect of solder. Benzoate is good for solder but it has less effect of aluminium. Hence, we have to use in the range of 0.5 to 1.2% which will take care of aluminum and solder in effective. Triethanolamine phosphate is used in the range of 0.3% to 0.8% as corrosion inhibitor for protection of Aluminium and cast iron. Di -potassium phosphate also used for the same purpose but the range is 1.0% to 2.0%. Phosphates are used in the range of 0.5% to 1.0% for protecting ferrous metals. Generally, borates are used in 0.8 to 1.0 for maintain pH (Buffer) of the coolant. Silicates also one of the good corrosion inhibitor and it is used in 0.020 to 0.040%. The structures of corrosion inhibitors are given in Figures 3 to 12. Carboxylic acids have good corrosion inhibitor for Solder and Aluminum but it has

limited inhibits compared to Dicarboxlic acid. However, with the combination of mono carboxylic acid and Dicarboxylic acid in correct dosage given excellent protection of both metals which has shown in results of sample “I” and sample “J”. Long chain dicarboxylic acid enhances protection of Aluminium and test results also proved the same.

Figure 3: Azole derivative.

Figure 4: Monocarboxylic acid -Type III.

Figure 5: Dicarboxylic acid-Type II.

Figure 6: Monocarboxylic acid -Type II.

Figure 7: Dicarboxylic acid -Type II.

3.3. Glassware Corrosion Test (ASTM D1384)

This method is a simple beaker method to evaluate the effects of engine coolants on metal specimens


under controlled conditions. Metal specimens are totally immersed in aerated engine coolant solutions for 336 hours at 88°C for high boiling coolant. The corrosion property of solution is evaluated on the basis of the weight changes on specimens. The test was carried out in triplicate and the average results were reported. The test results of all the samples coded as

A, B, C, D, E, F, G, H, I and J are given in Tables 3 to 8 and the pictures of metal coupons before the test and after the test were given in Figures 13 to 32. Aluminium weight loss was failing as per specification in sample A, B, C, D. This is due to absence of correct dosage of carboxylic acid with nitrite. The absence of azole in sample A, C, F, G and H leads to yellow metal corrosion, hence brass, solder and copper were on above the limit of specification. The presence of carboxylic acid gives good corrosion protection of solder, aluminium. The correct dosage of azoles and monocarboxylic acids protects yellow metals and ferrous however it was not protecting aluminium and solder in sample B, F and G. Sample C is meeting all metal corrosion except aluminium due to presence of Borax. Generally, borax will be good corrosion inhibitor for Aluminium but it gave lot of precipitate. Mono carboxylic acids and dicarboxylic acid in correct dosages will protect Aluminium and all ferrous metals, azoles with nitrite protects yellow metals, ferrous and solder. In sample D, azoles and nitrite protects yellow metals and ferrous. Also, the presence of “mono” and “di” carboxylic acid protects solder but it was not able to protect aluminium. Further, it gave some precipitates while on testing. Benzoate is a very good corrosion inhibitor for solder metals but it had less effect on cast iron. Samples I and J contains carboxylic acids and hence it meets almost all parameters, however sample I contains molybdate whereas sample J does not contain the same. All samples (A, B, C and D) were added with benzoate. The sample “E”, “I” and “J” has proper dosage of corrosion inhibitor and it meets all metal corrosion within the ranges. The test results of Glassware corrosion were shown in Tables 5 & 6.

Figure 13: Sample A - Glassware corrosion.

Figure 8: Dicarboxylic acid -Type I.

Figure 9: Monocarboxylic acid –Type I.

Figure 10: Tricarbxylic acid.

Figure 11: Monocarboxylic acid –Type IV.

Figure 12: Monocarboxylic acid-Type V.


Figure 14: Sample B - Glassware corrosion.

Figure 15: Sample C - Glassware corrosion.

Figure 16: Sample D - Glassware corrosion.

Figure 17: Sample E - Glassware corrosion.

Figure 18: Sample F - Glassware corrosion.

Figure 19: Sample G – Glassware corrosion.


Figure 20: Sample H- Glassware corrosion.

Figure 21: Sample I –Glassware corrosion.

Figure 22: Sample J- Glassware corrosion.

Figure 23: Sample A- Circulation corrosion.

Figure 24: Sample B- Circulation corrosion.

Figure 25: Sample C- Circulation corrosion.


Figure 26: Sample D- Circulation corrosion.

Figure 27: Sample E- Circulation corrosion.

Figure 28: Sample F – Circulation corrosion.

Figure 29: Sample G – Circulation corrosion.

Figure 30: Sample H – Circulation corrosion.

Figure 31: Sample I – Circulation corrosion.

3.4. Circulation Corrosion Test (ASTM D 2570)

This test method evaluates the effect of a circulating engine coolant on metal test specimens and


automotive cooling system components under controlled, essentially isothermal laboratory conditions. This test method, by a closer approach to engine cooling system conditions, provides better evaluation and selective screening of engine coolants than is possible from glassware testing (ASTM D 1384). In this method, prepared the test solution as per the method and measured its pH and reserve alkalinity for comparison after the test. The total test solution was required about 12 liters in circulation test. The polished and pre-weighed metal coupons assembled in bath as per method. Then poured 7 liters of test solution prepared as per method and solution was maintained at 88+/- 3 °C. This bath was connected with water pump and radiator through hoses. Continued the circulation for the specified duration under the condition as per method. After completion of testing, cooled the test equipment and calculated the changed weight / mass as per specification and the results were tabulated in Tables 7 & 8 and the metal coupons (specimens) pictures were shown in Figures 8-12. This method related to the life of the engine and how engine got corroded after one lakh kilometer in the field.

3.4.1. Sample A & C

The author tried to develop a coolant without Amine, Borate, Phosphate and silicate. But the presence of borates leads to better corrosion of Aluminium and maintains pH level. Hence, Borate was added in sample “A” and “C” and studied the corrosion behavior. Amines are very good corrosion inhibitor for Aluminium and cast iron. Also, amines were used in sample A, B and C. It was observed precipitate was appeared

during the testing of Glassware corrosion and circulation test and circulation test and hence it was failing as per specification.

3.4.2. Sample B, D, F, G & H

Mono carboxylic acid was added as corrosion inhibitor in sample “B” and sample “D”. This prevents the corrosion of Aluminium. In sample “D” contains three types of carboxylic acid which prevents the corrosion of Aluminium in effectively. G & H contains four types of carboxylic acids and it prevents Aluminium corrosion but fails in steel solder. Both the samples were contains nitrite which prevents the corrosion of cast iron and steel. Azole was added in sample “B” which prevents the corrosion of brass and copper. But azole was not added in sample “D” and hence it was failing for brass and copper. Benzoate was taken care of solder metal along with both carboxylic acid and had effect of aluminum and solder. The correct dosage of carboxylic acid was not used and hence yellow metal corrosion was failing in sample “F”. The correct combination of carboxylic acids were not used in “G” and “H” and hence samples were failing in solder and Aluminium.

3.4.3. Sample “E”, “I” and “J”,

Two types of mono carboxylic acids and Di Carboxylic acids were used in this formulation along with azole, nitrite and molybdate. Basically carboxylic acids were corrosion inhibitor of aluminium and ferrous metals. Copper and brass was protected by azoles and molybdate had protected solder. This sample was meeting both glassware corrosion test and circulation corrosion test.

4. CONCLUSION

Though conventional corrosion inhibitors were available for manufacturing radiator coolant for automobiles. Some of the chemicals were like Amines, Borates but these chemicals had adverse effects for nature and human kingdom. Most of the automotive industry is moving towards eco- friendly radiator coolants. In this study an effort was made to develop eco-friendly coolants.

• Sample B&C contains borates which good corrosion inhibitor and maintains pH level of coolant. Amines also added as corrosion inhibitor for protecting Aluminium and cast iron in sample “A”,”B” and “C” . These samples contain

Figure 32: Sample J – Circulation corrosion.


“nitrite” hence, it forms nitrozo amine which is carcinogenic and leads to cancer to animal kingdom. In view of this sample A, B and C not meeting environmental coolants.

• Sample D, F, G and H contains both carboxylic acids and eco- friendly chemicals but it was not meeting all metals specifications. The correct dosage and relevant chemicals were not used in the formulation.

• Sample E, I and J meets all metal corrosion for both corrosion tests and it was used eco-friendly chemicals.

This study will give the in-depth knowledge on anti – corrosion chemicals and its behavior with different metals and alloys. The metals manufacturer will find this study shows of glimpse of corrosion with metals. Also radiator coolant manufacturer may find this study a useful for their selection of eco- friendly chemicals for their formulation. This coolant has long life of the engine and other cooling system.

ACKNOWLEDGEMENTS

The authors express their gratitude to the Management of Bharat Petroleum Corporation Ltd. for granting permission to publish this work. Also, the authors would like to thank Shri V. Ananad, ED (Lubes), Shri M.K. Raut of Bharat Petroleum for their support.

HIGHLIGHTS

• Conventional corrosion inhibitors are used for coolant which are not eco- friendly. Based on this radiator coolants the energy consumption is more compared with eco-friendly coolants.

• Studied without using Amines, Borates, Phosphates and silicates for coolant.

• Environment friendly chemicals were used in this study for meeting specification.

• Completely organic acid technology meeting chemicals were used in this study which gives benefits to the environment. Also this formulation saves energy due to less corrosion of metals used in radiators.

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Received on 27-09-2019 Accepted on 11-10-2019 Published on 16-10-2019 DOI: https://doi.org/10.31437/2414-2115.2019.05.7 © 2019 Rajendiran et al.; Licensee Scientific Array. This is an open access article licensed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/3.0/) which permits unrestricted, non-commercial use, distribution and reproduction in any medium, provided the work is properly cited.

58 journal of mineral, metal and material engineering

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