Offshore

Nord-Lock Group has officially raised the corrosion resistance on all its steel wedge-locking washers and promises at least 1,000 hours in salt spray testing, ensuring optimum performance over time, even in the most extreme environments.

Corrosion is a growing concern across industries and the requirements are increasing in environments where accelerating factors such as humidity, heat and air pollution are combined. Corrosion occurs when metals come into contact with humid air or water, eventually weakening the steel parts and potentially affecting their function – forcing operators to increase repairs, which decreases productivity. It can impact structural integrity and therefore cause accidents. “Extreme environments demand more,” says Andrew Radnor, sales manager at Nord-Lock Group. “Corrosion will occur sooner or later and can jeopardise the whole application, not just the bolted joint.”

Generating 1,000 hours corrosion resistance
Understanding exactly how extreme factors such as pollution are affecting 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. Anders Knutsson, coating and corrosion expert at Nord-Lock Group, explains: “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.”

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 their high-quality standards, clearly shows that the washers generally endure much longer. “We have perfected our coating process so we can guarantee 1,000 hours. However, if you look at the results of the salt spray tests we do every week, the washers on average do endure over twice as long in the salt spray chamber before any signs of corrosion occur,” says Anders Knutsson. 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,” says Brian Troest. “Galvanised bolts are often used in construction,” continues Andrew Radnor. “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 propelled by a humid climate. “The high‑quality of the coating on the Nord-Lock washers allows us as a company to offer one washer to fit all the scenarios for steel,” says Andrew Radnor.

A stable production with rigorous process controls is the most important way to ensure that customers do not encounter problems in the field. “Our testing facilities with state of the art equipment in Europe, the United States, and Asia, combined with our collaborations with external test centres, allow customers all over the world to know that they can always rely on our quality,” says Andrew Radnor. “We also do customer specific tests if for example 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. Washers made from Alloy C-276 are the most reliable for acidic environments. Nord-Lock engineering services provide material and product selection guidance to ensure the best solution for every application.

Neutral salt spray test
The neutral salt spray test, (NSST according to ISO 9227), is one of the most established corrosion testing methods in the industry. It was designed to test the resistance of materials and surface coatings against corrosion, by exposing them to high concentrations of salt over a specific period of time. The test itself is conducted in a chamber with controlled atmosphere and level of corrosivity. The corrosive environment in the chamber can be altered depending on the type of material being tested. The suitability of the material or surface coating is judged by the length of time it takes for corrosion to appear.