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Metal Casting Technologies : June 2010
24 www.metals.rala.com.au 672-hour Coolant Corrosion Test -- Coolant Analysis and Engine Teardown Results An important task of the Project was to determine the potential for protecting the magnesium block from corrosion by the engine coolant, specifically in the presence of ethylene glycol water- based coolant. Extensive bench testing was done of all considered magnesium alloys in the earlier phase of the Project. After testing, the Honeywell experimental coolant was selected for the engine dynamometer coolant. Because the intended durability testing could not be done due to concerns about bulkhead failures (see above), the team chose to do a different durability test which was based on the Ford BL 102-02 standard for screening coolant behaviour. This test simulates on-road engine cycles for a small vehicle. The major change to the test protocol was to run the engine at low load; low enough to protect the bulkheads, but high enough to achieve the necessary coolant temperatures to effectively test the coolant/ component interfaces. The engine was run at 2000 rpm at 50 kN with periodic high and low temperature soaks. The test duration was forty-two days. Testing went well and no issues were reported, including no indication of bulkhead failure as was reported during break-in for the DTS test (see above). Coolant samples were drawn before and after the test and at 96-hour intervals. The coolant samples were clear to visual inspection and free of sediment. Analysis of the coolant showed negligible build up of magnesium, iron, and zinc over the 672 hr of engine operation. This was further evidence that the coolant formulation did protect the magnesium from corrosion. Visual inspection of the cylinder block and microscopic inspection of the internal coolant passages showed a slight discoloration of the metal surface, but otherwise minimal corrosion. These results indicate that corrosion of magnesium in engine coolant is not a showstopper for the magnesium-intensive engine. NVH assessment of the magnesium-intensive engine It is generally assumed that because of its lower density and stiffness, magnesium engine components will have worse NVH performance than aluminium and iron components. The MPCC project team originally intended a cursory NVH assessment of the magnesium-intensive engine, but when it was observed how relatively quiet the engines were, a new task was added to the Project: a quantitative assessment of the NVH performance of the MPCC engine, the original aluminium production engine and engines with sequential substitution of magnesium components for the original aluminium components. This assessment was completed in FY 2009. Six engines were prepared and tested in sequence in the test fixture. Block Oil Pan Front cover Al Al Al Al Mg Al Al Al Mg Al Mg Mg Mg Al Al Mg Mg Mg Table 1. Hardware Configurations for NVH Testing Figure 1. FEA safety factor (S.F.) predictions for bulkhead #1 in vicinity of M8 bolt hole: original FEA (left) and revised FEA (right). LIGHT METALS R&D