Tag Archives: Corrosion

Protecting Fasteners from Corroding Part 1: Basics of Corrosion and Protection Mechanisms

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Reprint from China Fastener World Magazine, Vol. 190

The man walked to his tool box, selected the right sized socket and returned to the piece of machinery he was trying to repair. He stared for a moment at the nut he was trying to loosen. It was badly corroded but he had done this many times before. Carefully seating the socket fully on the nut he began to apply pressure. At first nothing happened but then he felt a tiny change in the resistance, reinvigorating his incentive to keep pushing on the bar. Just as he thought he had given it his all, a resounding loud snap occurred catapulting him and his tools forward as his efforts were no longer restrained by the once stubborn but now broken bolt and nut. Crashing into the floor, he yelped in pain and cussed his misfortune.

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Fastener Corrosion in Treated Lumber

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Reprint from China Fastener World Magazine, Vol. 44

Fasteners, whether they are nails, screws, anchors, or metal connectors play a critical and important role in wood/timber construction. In essence, these products are critical in joining materials together and either carrying
or helping distribute structural loads. In many instances these fasteners are installed in corrosive environments or brought into contact with corrosive materials. Common examples of these conditions include exposure to constant moist or humid conditions, coastal conditions or salt infused air, preservative-treated lumber, and contact with dissimilar metals. Any one or a combination of several of these factors can conspire to corrode a poorly specified fastener resulting in loss of the load carrying capacity of the joint, either by degradation of the fastener, the surrounding wood, or both. Therefore, the specifier of the fastener must be knowledgeable about the service conditions and make prudent selections of the fastener coating or raw material to minimize these risks.

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Galvanic Corrosion: Knowing How It Works and Steps to Protect It Are Important

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From Fasteners Technology International, April 2014

Anyone that has ever worked on rehabbing an older home has probably encountered a plumbing connection where an old galvanized steel pipe that has been connected with a newer copper fitting such as shown in Figure 1 is in bad shape. The discovery of this condition may be purely accidental, or more likely, if such a connection has been in-place for any length of time, the ticking time bomb represented by this condition has finally gone off and it is leaking or broken.

So what is this condition? It is a classic case of galvanic corrosion. Fastener engineers, designers and end users, especially in instances where metals are being clamped in wet environments, must be very wary of this possibility and make efforts to avoid future problems.

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Is It Worth Its Salt?

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From Fastener Technology International, October 2012

In the early days of my career, when I was occasionally working on new part approvals, and then later when I was overseeing such activity, a common and frustrating event was to discover that parts submitted to the customer for approval did not pass their salt spray test. This was particularly confounding because those same parts would have passed our internal testing and often that of our plating vendor. I would quickly come to learn that this is a common industry problem and one likely experienced by every fastener manufacturer or distributor at one time or another.

To compound this frustration, I learned that although the experts have long debated the pluses and minuses of this test, regardless of which side they fall, they universally agree that this test may not provide similar results between test cabinets (even though all process parameters have been followed) and that the mechanism of failure is so radically different from real world application, that there is no known or accepted correlation between salt spray hours passed and actual performance in real-world service.

One might logically ask then, what the value of this test is, what is really happening amid that salt fog and why other test methods haven’t replaced it. The following is an attempt to understand more about the process and tackle these and other questions regarding this universal and deep-rooted test method in qualifying fastener quality and ability to withstand service corrosion conditions.

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