Summary for anodizing aluminum screws Discussion
Anodizing Al precision miniature screws is discussed as a possible way to replace titanium in lightweight electronic fasteners, but the replies are cautious. The original poster asks whether aluminum screws/inserts can be batch anodized without racking and whether the anodized layer will survive assembly. Can Pi suggests trying basket or barrel anodizing, noting that mostly threaded parts with larger heads may minimize contact marks, but there is no guarantee of success and each part should be checked with a conductivity test. Dado Macapagal recommends considering a high-strength aluminum alloy with Alodine or Iridite instead of relying on anodizing. Robert H. Probert adds the key warning that anodic film on sharp edges such as threads becomes 100% aluminum oxide, which is very brittle and can break off. Overall, the thread leans against assuming anodized aluminum screws will tolerate automatic assembly without damage.
Q. Hi,
I am doing technology development job in company supplying precision fasteners/parts to electronic industry, e.g. cell phones and tablets.
There was inquiry from customer that they wanted some screws/inserts that are very light. We tried out both Al and Ti. Because Ti has much higher strength and hardness so customer finally opted for Ti.However, machining Ti has a very high cost.
I am thinking if the Al screws/inserts are subjected to anodizing followed by sealing, it might be able to replace Ti in such kind of application.
My question:
1. is it possible to do anodizing in batch process, without racking of the screws?
2. is the anodized layer very brittle? after assembly the screw, will the anodized layer remain intact?
I am very new in this area, please kindly give your comment. Thanks
Can Pi
fastening surface technology – Singapore
A. You might want to try ‘basket’ or ‘barrel’ anodizing. I assume that the part being mostly threaded, and with larger head than the stem, will result to minimum contact marks. There is no guarantee for 100% success. You will have to check each part using conductivity test. Why not use Al high strength alloy and temper, coated with Alodine or Iridite instead?
Dado Macapagal
– Ont., Canada
A. The anodic film formed on a sharp edge, like a thread, becomes 100% aluminum oxide, is very brittle, and breaks off.
Robert H Probert
Robert H Probert Technical Services
Garner, North Carolina
December 7, 2012
Thanks for your replies.
If the anodized layer is very brittle, it is then not able to withstand the impact during automatic assembly.
Can Pi
– Singapore