The anti-corrosion surface treatment of fasteners 02 March 2021

Recently there has been an increase in demand for the hot dip galvanising of threaded rods up to Grade 10.9 – used as anchoring in the construction of wind turbines, geotechnics, hydro engineering and the general construction industry. Thielco Steel Solutions Group has responded to this demand by developing a unique production line specifically for these products, to enable rework-free hot dip galvanising.

Proper corrosion protection extends the life of fasteners significantly, hereby contributing to longer maintenance intervals and general lifecycles of the construction in which they are applied. With the ever increasing requirements for sustainability, it is not unexpected that parts that traditionally did not get any corrosion protection treatment, due to costs or technical limitations, now do need to be treated to meet the demands. Hot dip galvanising is the obvious way to go – by dipping a steel product in hot, liquid zinc, a zinc layer forms that alloys with the steel, providing a strong protection against corrosion. 

Zooming in on full threaded rods/anchors of M20 – M56 up to 4,000mm, the first challenge is to keep the thread clean of zinc residue. Where shorter parts can be centrifuged to sling off excess zinc after dipping, to achieve a clean thread, this is not possible with longer products. Up until now, to preserve the function of the thread, they had to be reworked either manually with a steel brush or rerolled by a thread rolling machine, adding a process step and damaging the zinc layer.

Using the new facility, the anchors are instantly and non mechanically cleaned after galvanising, in-line, while they are still hot. This leaves the zinc layer fully intact and the product is ready to be used immediately if required.

As the rods are galvanised horizontally, instead of vertically, there are no differences between zinc layer thickness on both sides of the product and no drops or sharp edges will form on the lowest point.

As with all Thielco processes, the risk of hydrogen embrittlement is absent, using adjusted pre-treatment systems, which are constantly measured and documented. Moreover, the process is fully automated and recipe driven, ensuring full replicability of results as well as perfect traceability of each and every production batch.

Thielco aims to deploy this innovative facility to support the supply chain partners in working leaner and smarter to maintain a strong competitive position in the world. From the strategic location on the Dutch-German border, Thielco serves customers throughout Europe with short lead times and high flexibility.

Deputy Editor

Claire Aldridge Deputy Editor t: +44 (0) 1727 743 889


Having joined the magazine in 2012, Claire developed her knowledge of the industry through the numerous company visits, exhibitions and conferences she attended both in the UK and abroad.

Claire prides herself on keeping readers well informed and up to date with the latest industry news.