The iPhone 5 came out just this past weekend, and in the first three days Apple sold about 5 million of them.  This sounds like a great success, but is there a problem with the durability of the new product?  What do we even mean when we talk about durability?

One of the big design changes to the iPhone 5 is the change of the case from a glass back with stainless steel band to a design in which both are made of anodized aluminum.  The change of the back from glass to aluminum will certainly prevent the cracked cases that many users experienced from dropping their phones, but does it introduce a new problem?

Aluminum: the Good and the Bad

Aluminum naturally forms a coating of aluminum oxide through regular oxidation (known as passivation).  This coat is very hard and prevents further oxidation.  Anodization is the method of increasing the thickness of this oxide layer using electrochemistry.  In addition, the thickened layer can be dyed a variety of colors.  This is the process used on the new iPhone’s back and band.

While the newly created oxide layer is very hard, the downside is that scratches are clearly evident on colored anodized parts, as the scratches will show the silvery aluminum metal beneath.  Even industry advocacy groups warn that for parts that will be viewed up close anodizing may be a poor choice, as even small scratches can noticeably detract from the appearance (http://www.anodizing.org/FAQ/faq_cont2.html - “Can anodizing hide scratches?”).

This design choice has led many users to complain about the durability of the phone’s finish, especially on the black model.  The repair website iFixit has a great video showing the durability problems that these users face very clearly.

Lessons to be learned

So, what can we learn from this issue?  Firstly, engineers and designers must be very careful when choosing which materials to use in their new products.  This is especially true if the product is going to face physical abuse in its everyday usage (such as sitting in a pocket with keys and other metal objects repeatedly hitting and scraping it).  The original iPhone actually wore very well, and looks great after years of use.

In this harsh use situation brushed stainless steel would be a better choice for hiding scratches, although of course it would be heavier if the dimensions remained the same.  Perhaps an uncolored anodized coat would be a good choice if aluminum was still to be used.  You could also use a much thicker anodized layer, informally known as hardcoat anodization, which stands up better to scuffs and scratches.  All of these choices help the beauty of your product last much longer, and enhance the experience for the user.  

And finally, if you’re thinking about buying the iPhone 5, make it the white one.