Corrosion is a growing concern across industries, with requirements increasing in environments where accelerating factors, such as humidity, heat, and air pollution, are combined. The Neutral Salt Spray Test (NSST) according to ISO 9227 is one of the most established methods to verify corrosion resistance.
The corrosion resistance of all steel wedge-locking washers with zinc flake coating from Nord-Lock Group promise at least 1,000 hours in a salt spray test. However, constructors can expect significantly more hours than that, as Nord-Lock washers consistently surpass 1,000 hours easily during tests. These NSSTs ensure optimum performance over time, even in the most extreme environments.
Corrosion occurs when metals come into contact with humid air or water. Corrosion will eventually weaken steel parts and can potentially impact their function, forcing operators to increase repairs which decreases productivity. It can impact structural integrity and therefore cause accidents. Extreme environments demand more, but regardless, corrosion will occur sooner or later and can jeopardise the whole application, not just the bolted joint.
Understanding exactly how extreme factors such as pollution are impacting applications and using this experience as the basis for product developments is increasingly important. Whatever the environment, Nord-Lock Group collaborates with customers globally to meet needs and specifications, including providing necessary certifications.
“Customers need washers that can withstand extreme environments for a longer period of time. Based on this, we continuously put more focus on increasing the corrosion resistance of our standard products,” explains Anders Knutsson, coating and corrosion expert at Nord-Lock Group.
Although 1,000 hours is the official number released by the Group, this is just the minimum amount of time Nord-Lock steel washers with zinc flake coating by Delta Protekt® can withstand corrosion in a salt spray test. The quality testing the Group does, as part of ensuring its high-quality standards, clearly shows the washers generally endure much longer.
“We have perfected our coating process so that we can guarantee 1,000 hours. But if you look at the results of the salt spray tests that we do every week, the washers on average do endure way longer than that in the salt spray chamber before any signs of corrosion occur,” highlights Anders. According to ISO 12944-6:2018, 1,000 hours in a salt spray chamber corresponds to at least C4 High or C5 Medium conditions.
The Nord-Lock standard range includes Nord-Lock Original Washers and X-Series washers, with standard and enlarged (SP) outer diameter, and Steel Construction (SC) Washers. High corrosion resistance for such a large range of washers allows customers to secure applications when facing a wide variety of challenges. This is especially helpful when the industry uses galvanised bolts which, combined with Nord-Lock steel washers, provide a very high corrosion resistance for the whole assembly.
Galvanised bolts are used within the wind power industry and according to Sales Manager Brian Troest, pairing them with Nord-Lock steel washers is very beneficial as more and more wind turbines move offshore. “Steel washers are used onshore and offshore, inside the towers and on blade bolts, where they can be exposed to the environment,” highlights Brian.
Galvanised bolts are also often used in construction. If steel washers are used in a polluted environment with galvanised bolts, the combination is very durable against corrosion.
Developing products for global use
Big cities in Europe and the rest of the world are facing difficulties with a high-level of pollution. In some parts of the world, Asia for instance, corrosion is also propellered by a humid climate. The high-quality of the coating on the Nord-Lock washers fits all ranges of potential climate scenarios that the steel might face.
A stable production with rigorous process controls is the most important way to ensure customers do not encounter problems in the field. Nord-Lock’s testing facilities with state of the art equipment in Europe, the United States and Asia, combined with collaborations with external test centres, enables its customers all over the world to know they can rely on its quality. Nord-Lock Group also performs customer specific tests if a specific assembly needs verification .
Washers for even tougher environments
Oil and gas applications, power generation, and industrial machinery, must operate in some of the most aggressive conditions on Earth. Nord-Lock washers made of 254 SMO™ are specifically developed to protect bolted joints in saltwater applications. As well as this, washers made from Alloy C-276 are the most reliable for acidic environments.
Nord-Lock Group will continue to provide material and product selection guidance to ensure the best solution for every application.
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