The signs your springs are about to fail

Corrosion is the deterioration of a metal surface because of an electrochemical process between it and the surrounding environment. Interestingly, corrosion is not usually the sole cause for failure. Rather, it creates pits on the surface, which act as stress concentration points, resulting in premature fatigue failure. Corrosion can also lead to embrittlement
of the material, causing more catastrophic failure. 

Identifying corrosion

When the Institute of Spring Technology receives a broken spring, it examines it by eye for any obvious signs of a failure method. Corrosion is usually fairly easy to see, as there is typically some discolouration on the wire's surface. It is also identifiable by surface
pitting. Pits can be small or large, depending on the length of exposure, the amount, and the strength of the corrosive substance present.

Once the initial examination has been completed, it's time to move to the microscopes for a more detailed view. The entire spring is examined, and this will indicate if the corrosion
is widespread or localised to smaller areas. The company also checks to see if there is any substance left on the spring or damage to the region. Residual substances could be from oil or cleaning products, both of which could give an idea of why the corrosion started. Localised damage, scratches etc., are also identified
– these could remove any corrosion protection, accelerating corrosion.

After the severity of pitting has been identified, IST can aim the analysis to more focused areas. Close-up images, especially around the initiation, are taken so the final report can be as informative as possible, allowing IST’s client to see the problem areas.

Read the full article in DPA's November issue