IEC Earthing Bond: Allowed Bolt/Screw Materials and Corrosion Concerns?

Hey there everyone,

Got some question on earthing standard. Is IEC Standard ever stated type of material for bolt/screw that shall be clamp with earthing wire?

Right now I'm going to use a Zinc Coated screw for earthing bond instead of brass or stainless steel, but all known that zinc coated easy to rust under humid condition. If the zinc coated screw start to rust, will it spread through other contact surface?

Please advise.

Thanks.

The LPS designer and the LPS installer should select suitable types of earth electrodes and should locate them at safe distances from entrances and exits of a structure and from the external conductive parts in the soil, such as cables, metal ducts, etc.

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Zinc  plated screws don't rust, only the underlying steel if the galvanizing is removed. It does form a white oxide. A bit more detail would be useful, is this an outside application, as on for instance an earth stake, or in a piece of interior electrical/electronics equipment . What sort of  ambient humidity are you dealing with.The screw only acts as a clamp, the lug that the earth wire is attached to and they way it makes contact with the underlying metal which it is to be bonded to is the most important issue. Galvanic corrosion can be a problem since invariably different metals are in contact with one another, and this will be exacerbated by high humidity, this may be controlled by applying paint or grease over the bolt and and the region around it.I worked in a laboratory, and was sometimes called in to test products to the appropriate standards. The only test done on the earth lug was to verify that after removing and replacing the earth  self tapping screw a number of times that the thread in the metal was still intact. Most of the screws used were zinc plated, and washers were often not used. The most common failure was a stripped thread in the thin sheet metal, which meant a redesign.Cheers,Richard

Hi Richard,Thanks a lot for the explanation. As you can see below, the application to be use inside HVAC system and high humidity expected inside. Stainless steel out of choice due to the high cost. Copper and zinc are bad combination which lead to rust right? Which remain Tin and Brass. Which material suitable for this application?