Corrosion Prevention: When Protection is Broken
What Happened?
One side-effect of being a forensic materials analyst is noticing slight issues in everyday life, that you can forsee becoming a big problem in the future. But you can’t always do something about it. In a small industrial estate near to where our laboratory is located, there was growing issue of cars being parked along footpaths and causing obstructions. After many complaints, barriers were erected, bolted into the concrete foothpath. After a couple of weeks though, I could see a problem starting to grow, right out from the bolts. A layer of corrosion on the surface of the bolt, staring up into the sky. Looking closely, it seemed like the tail of the bolt had been cut off, to keep it flush and in line with the nut.
How did we analyse it?
In this case, no analysis was required, just human eyes and some simple deduction. Most mechanical fasteners used in such applications will be some form of steel, whose propensity to rust is well known. It is a reasonable assumption that the bolt and nut had been protected against rusting, probably through a zinc coating applied to the surface of the nut and bolt. But then, when the tail of the bolt was cut off, it removed the protected surface and exposed the interior, unprotected surface of the bolt. Add in pooling rainwater, and rusting of the bolt becomes inevitable. The worst part is, this corrosion will continue to happen, until the entire inner core of the bolt has rotten away.
If we were to analyse it, we would use SEM-EDS to determine the elemental composition of the bolt, both on the surface and on the exposed internal face. We would expect to see high zinc concentration on the surface with little iron, while the internal face should have high iron concentration with almost no zinc. But we could only do such analysis with permission from the property management company…
What was the resolution?
So far, nothing! I wrote to the property management company, advising them of this issue, which I could forsee growing if not addressed. But six months later, the bolts remain in place, and continue to rust. I plan to follow-up in another six months, at which point, who knows how much the bolt will have corroded? I think it’s unlikely that this particular corrosion will result in any personal injuries, but its not impossible. At the very least, the hard work done in erecting the barriers will have to be redone. It all could have been prevented with a simple 5-minute chat!
Have you seen a small problem growing? Or maybe you’re concerned one is about to start? For a science-supported, evidence-based Expert Opinion, be sure to Contact Us today!
