Corrosion Resistance Compare between A380 and A360 die casting aluminum

Both A380 and A360 die casting aluminum alloy belong to Al-Si-Cu Aluminum.Al-Si-Cu alloy feature excellent castability,low shrinkage rate and low hot crack possibility.It is very common die casting alloy and mainly used for automotive parts,mechinary parts,hydraulic parts,etc.A380 is most common in die casting production.It contain about 7.5%-9.5% silicon,which is very useful for castability.The Cu composition is about 3.0%-4.0%,which acquire good strength and machining ability.Therefore,it is wildly used in automotive,aerospace,electric industry.However,due to high Cu composition,the corrosion resistance of A380 is not good.A360 is kind of common Al-Si-Cu alloy and similar to A380.However,A360 only contain about 0.6% Cu and has better corrosion resistance than A380.A360 has poor welding ability so it common usage is for kind of housing and shell.

Compostion	Si	Cu	Mg	Fe	Zn	Mn	Sn	Ni	Balance
A360	9.0-10.0	≤0.6	0.4-0.6	≤1.3	≤0.5	≤0.35	≤0.15	≤0.5	AL
A380	7.5-9.5	3.0-4.0	≤0.1	≤1.3	≤3.0	≤0.5	≤0.35	≤0.5	AL

To compare corrosion resistance between A380 and A360.The casting parts made in both material are put into NaCl solution.The corrosion area on A380 casting parts are much more than A360 casting parts.By calculation,corrosion rate of A360 is 0.124mm/a,while A380 is 0.153mm/a.

The corrosion electric potential for A380 and A360 is -700mV and -400mV.Therefore,corrosion possibility for A360 die casting parts is much lower than A380.Within range from -400mV-+40mV,A360 has passivating layer which can protect from corrosion.When electric potential is more than +40mV,passivating layer lose function and corrosion happen.However,A380 do not have passivation layer and will be corroded directly.

Both A380 and A360 die casting parts have spot corrosion after putting into 3.5% NaCl solution.
The corrosion happened onto A380 is much worse than A360.Cu element mainly cause poor corrosion resistance on A380 alloy.In order to improve corrosion resistance,the composition of Cu must be lower.
Electric potential of A360 is 300mV higher than A380,which will create passivation layers on the A360.A380 do not have such layer,which lead to poor corrosion resistance.

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