Stainless Steel is known for its strength and resistance to corrosion.

Whereas, HDG fixings should be used for outdoor applications open to the weather and also indoors where conditions may be damp or wet. So, when choosing between the two finishes, it’s reasonably simple BZP fixings are great for indoor dry climates where only superficial protection is needed and an element of aesthetic value is desired. One final consideration is that if the protective zinc layer is damaged such as when HDG products are cut, then a galvanising spray should be used to cover the exposed area in order to continue providing protection.īoth BZP and HDG add a protective layer of zinc to steel although typically a BZP Zinc plating will be 3 microns thick and the HDG protective Zinc layer will be 50 microns thick, hence the far stronger protection offered by galvanised fixings. For example, the use of HDG nuts should be used with HDG bolts and HDG threaded rod.Īlthough duller in appearance and not as aesthetically pleasing as other finishes such as BZP, with its strong corrosion protection galvanised fixings offer the advantage of being low maintenance once installed and can be used for outdoor applications. HDG fasteners have an oversize tap which accommodates the extra layer of zinc allowing each fastener to fit together neatly. So, you’ll need to use a set of HDG fasteners for all parts of the fixing. It’s important to consider that when threaded fasteners are Hot Dip Galvanised, the size of the thread increases due to the protective layer of zinc. Hot Dip Galvanising offers a cost-effective method to provide a strong weather resistant finish which protects steel from corrosion. HDG stands for Hot Dip Galvanised and refers to a process where the finished fixings and fasteners are dipped in a bath of molten zinc which bonds with the steel to provide a protective layer (thicker than BZP plating). A BZP finish also has the advantage of being aesthetically pleasing, with the fixings used looking bright and shiny. Hence BZP is a good choice for indoor applications.Īs BZP is a standard low cost finish, freely available for most types of fixing, specifying it can help keep all the fixings used on an installation uniform. Although the BZP finish makes the steel fixings resistant to moisture, the layer of zinc is only thin so it won’t prevent rusting or oxidising if the fixings are used externally. The applied layer of zinc then offers galvanising protection to the steel fixings to prevent rusting or oxidising. Essentially a thin layer of zinc is applied to the fixings using an electric current. Bright Zinc Plating is a process that is applied to standard steel or alloy fixings during their manufacture. Whereas although it has a higher cost and is potentially harder to work with, stainless steel offers the advantages of strength and increased corrosion protection, as well as providing a quality finish that’s aesthetically pleasing.įor ease we will focus on comparing BZP and HDG and then types A2 and A4 Stainless steel, before providing a summary of considerations for choosing each one.īZP stands for Bright Zinc Plated and is the most common finish for the majority of fixings and fasteners. In this blog post we summarise each finish and try to highlight the key differences between them.īright Zinc Plated and Galvanised steel are the most common types of fixing finish, are easy to work with and offer a lower cost option than stainless steel.

With Stainless Steel typically split between A2 and A4 types. There are three common finishes for steel fixings and fasteners BZP – Bright Zinc Plated, HDG – Hot Dipped Galvanised and Stainless Steel.

Does zinc screws rust