Composition of alloy play negative effect on anodizing.At same condition,Pure aluminum can achieve best finishing of anodizing.To get best anodized aluminum,the composition of aluminum can not be lower than 95%.
Among elements of alloy,copper can make anodizing become red and increase defects of oxide.Silicon will turn anodizing into gray and finishing become worse when composition of silicon over 4.5%.Iron will turn into black after anodizing.
Die casting aluminum alloy normally contain high amount of silicon so anodizing turn to dark gray and it is impossible to get clear anodizing.As increase of silicon,anodizing will change from gray colour to black colour gradually.Therefore,die casting aluminum is not suitable to anodizing.
Common die casting aluminum include mainly three categories as following
- Silicon Aluminum:ADC1,ADC3,A360 etc
- Silicon Copper Aluminum:A380,ADC10,A383,ADC12,B390,ADC14
- Magnesium Aluminum:ADC5,ADC6