Testing of Organic Acids in Engine Coolants

Weir, T. W.

doi:10.1520/stp38236s

Cited by 5 publications

(5 citation statements)

References 4 publications

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“…The adsorption of 1 Open circuit potentials of GW103 and AZ91D in blank EG solution and solutions with sodium phosphatezSDBS and sodium phosphatezbenzoate respectively EG molecules may repel water molecules and protect the Mg alloy surface to some extent. 19 The OCP behaviour after addition of the inorganic-organic inhibitors should be associated with formation of a relatively uniform deposited or adsorbed film on the Mg alloy surfaces. 24 The film reduces both the cathodic and anodic reaction rates; the anodic processes could be retarded more significantly.…”

Section: Resultsmentioning

confidence: 99%

“…In general, the increase in OCP with time in the blank solution could be associated with the adsorption of EG molecules at the Mg alloy interfaces. The adsorption of EG molecules may repel water molecules and protect the Mg alloy surface to some extent 19. The OCP behaviour after addition of the inorganic–organic inhibitors should be associated with formation of a relatively uniform deposited or adsorbed film on the Mg alloy surfaces 24.…”

Section: Resultsmentioning

confidence: 99%

“…10 For example, in addition to selfcorrosion, it has been realised that the galvanic corrosion of magnesium alloy coupled to other metals is one of the difficult obstacles in the application of magnesium alloys as structural materials in automotive industries. [11][12][13][14][15][16][17][18][19][20] When two different metals are coupled, the metal with a relatively negative potential will be an anode and undergo accelerated anodic dissolution by the other one with a relatively positive potential. The galvanic corrosion rate of two coupled metals in direct contact with identical size can in theory be determined by 10 i g ~Ec {E a R a zR c zR s zR m (1) where i g is the galvanic current between the anode and the cathode, E c and E a are the corrosion potentials or open circuit potentials (OCPs) of the cathode and anode, R c and R a are the cathode resistance and anode resistance respectively, R s is the solution resistance between anode and cathode and R m is the metal resistance from anode surface to cathode surface through a metallic contact, which is negligible if the two metals are in a direct electrical contact.…”

Section: Introductionmentioning

confidence: 99%

“…Inhibitors are essential components in a coolant to protect traditional engine materials, such as cast iron, aluminium, copper, steel and lead-tin solder. 19,20 However, traditional inhibitors including imidazole, amine, borax, carboxylate, etc., [21][22][23] which were developed for traditional materials, such as steel, copper or aluminium, do not give adequate protection for magnesium alloys. 24 In a cooling system, both selfcorrosion and galvanic corrosion can occur.…”

Section: Introductionmentioning

confidence: 99%

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Self-corrosion, galvanic corrosion and inhibition of GW103 and AZ91D Mg alloys in ethylene glycol solution

Huang

Song

et al. 2013

Corrosion Engineering, Science and Technology

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The self-corrosion and galvanic corrosion of magnesium based alloys Mg-10Gd-3Y-0?5Zr (GW103) and AZ91D coupled to carbon steel and Cu in ethylene glycol (EG) solution with and without inorganic-organic inhibitor packages Na 3 PO 4 zSDBS and Na 3 PO 4 zbenzoate were investigated through measuring their open circuit potentials, coupling potentials, potentiodynamic polarisation and galvanic current densities. It was found that these two inhibitor packages effectively inhibited the self-corrosion of GW103 and AZ91D but accelerated the dissolution of the carbon steel and Cu in the EG solution. When the Mg alloys were coupled with the carbon steel or Cu, their galvanic current densities were also inhibited if the Na 3 PO 4 zbenzoate inhibitor package was used in the EG solution. It is surprising that the addition of Na 3 PO 4 zSDBS accelerated the galvanic corrosion. Based on the mixed potential theory, it is believed that the variation in E corr difference between the anode and cathode and the change of their Tafel slopes after inhibitor addition should be responsible for the galvanic corrosion behaviour of these couples. Corrosion Engineering, Science and Technology 2013 VOL 48 NO 2 Huang et al. Self-corrosion, galvanic corrosion and inhibition of GW103 and AZ91D Mg alloys in ethylene glycol solution Corrosion Engineering, Science and Technology 2013 VOL 48 NO 2

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Self-corrosion, galvanic corrosion and inhibition of GW103 and AZ91D Mg alloys in ethylene glycol solution

Huang

Song

et al. 2013

Corrosion Engineering, Science and Technology

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“…Inhibitors are normally essential components in a coolant to protect traditional engine materials, such as cast iron, aluminum, copper, steel, and lead-tin solder. [19][20][21] However, traditional inhibitors do not give adequate protection for Mg components, particularly against the galvanic corrosion at high temperatures (80°C to 100°C) that a working engine has to experience. There is a need for a coolant that can provide a high level of protection for Mg components against galvanic corrosion.…”

Section: The Galvanic Corrosion Of Gw103 and Az91d Coupled To An Al Amentioning

confidence: 99%

Galvanic Corrosion and Inhibition of GW103 and AZ91D Mg Alloys Coupled to an Al Alloy in an Ethylene Glycol Solution at Ambient and Elevated Temperatures

Huang¹,

Hu²,

Song³

et al. 2012

CORROSION

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The galvanic corrosion of GW103 and AZ91D coupled to an Al alloy (Al 7005 [UNS A97005]) in an ethylene glycol (EG [C 2 H 6 O 2 ]) solution at ambient (25°C) and elevated temperatures (90°C) was investigated using open-circuit potential (OCP), coupling potential (CP), galvanic current density, potentiodynamic polarization curve, and electrochemical impedance spectroscopy (EIS). Moreover, weight-loss measurement and scanning electron microscopy (SEM) also were used to investigate the galvanic corrosion damage of the coupled Mg alloys. The galvanic corrosion behaviors of the couples were compared in the EG solution before and after a combination of inorganic inhibitor sodium phosphate (Na 3 PO 4 ) and organic inhibitor sodium dodecylbenzenesulfonate (C 18 H 29 NaO 3 S) was added to the solution. It was found that both the general corrosion and galvanic corrosion of the Mg alloys were mitigated by the organic-inorganic inhibitor package. The most interesting finding was that the anode and cathode of the Mg alloy-Al alloy couples were reversed by adding inorganic and organic inhibitors into the blank EG solution. The anode-cathode reversal can be attributed to the OCP changes of the anode and cathode after inhibitor addition. The measured galvanic behavior was in good agreement with the mixed-potential theory predictions.

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Corrosion of magnesium alloys in commercial engine coolants

Song

StJohn

2005

Materials and Corrosion

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A number of magnesium alloys show promise as engine block materials. However, a critical issue for the automotive industry is corrosion of the engine block by the coolant and this could limit the use of magnesium engine blocks. This work assesses the corrosion performance of conventional magnesium alloy AZ91D and a recently developed engine block magnesium alloy AM-SC1 in several commercial coolants. Immersion testing, hydrogen evolution measurement, galvanic current monitoring and the standard ASTM D1384 test were employed to reveal the corrosion performance of the magnesium alloys subjected to the coolants. The results show that the tested commercial coolants are corrosive to the magnesium alloys in terms of general and galvanic corrosion. The two magnesium alloys exhibited slightly different corrosion resistance to the coolants with AZ91D being more corrosion resistant than AM-SC1. The corrosivity varied from coolant to coolant. Generally speaking, an organic-acid based long life coolant was less corrosive to the magnesium alloys than a traditional coolant. Among the studied commercial coolants, Toyota long life coolant appeared to be the most promising one. In addition, it was found that potassium fluoride effectively inhibited corrosion of the magnesium alloys in the studied commercial coolants. Both general and galvanic corrosion rates were significantly decreased by addition of KF, and there were no evident side effects on the other engine block materials, such as copper, solder, brass, steel and aluminium alloys, in terms of their corrosion performance. The ASTM D 1384 test further confirmed these results and suggested that Toyota long life coolant with 1%wt KF addition is a promising coolant for magnesium engine blocks.

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Testing of Organic Acids in Engine Coolants

Cited by 5 publications

References 4 publications

Self-corrosion, galvanic corrosion and inhibition of GW103 and AZ91D Mg alloys in ethylene glycol solution

Self-corrosion, galvanic corrosion and inhibition of GW103 and AZ91D Mg alloys in ethylene glycol solution

Galvanic Corrosion and Inhibition of GW103 and AZ91D Mg Alloys Coupled to an Al Alloy in an Ethylene Glycol Solution at Ambient and Elevated Temperatures

Corrosion of magnesium alloys in commercial engine coolants

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