Tinned Copper Earth Bars – How To Specify The Correct Earth Bar

Published 06 Jun 2018

Earth Bars – manufactured from 50x6mm Tinned Hard Drawn Copper Bar

• Uploaded by Chris Dodds - Thorne & Derrick Sales & Marketing Manager

Earth Bars

Advantages & Applications Of Tinned Copper

The following article has been written to provide some basic advice and reasoning for the specification of Tinned v Standard Copper Earth Bars when designing earthing systems for LV MV HV building services and substation protection exposed to wet conditions during normal operation.

Copper is used in the manufacture of Earthing & Lightning Protection Systems due to the high thermal and electrical conductivity, ease of manufacture, high recyclability and good corrosion resistance of the material. Copper, a noble metal that occurs naturally in its elemental form, is almost totally impervious to corrosion from soils found worldwide.

But it would be misleading to infer that copper will not corrode.

Tinned copper is a type of copper coated with a thin layer of tin used to provide protection to earth bars against the tarnishing and corrosive effects of oxidisation, commonly referred to as rusting.

The thin layer of tin effectively shields the copper surface of the earth bar inhibiting oxidisation – preventing air from reacting with the copper in the presence of atmospheric moistures. Put simply – no air, no oxide, no corrosion.

The copper tinning process provides enhanced protection against climatic variations and atmospheric conditions without significant reduction in the functionality and electrical conductivity of the copper metal.

Oxidised copper surfaces display poor conductivity compared to clean and smooth tinned copper which prolongs the service life of the earth bar at comparatively low added-on cost.

Tinned copper is higher cost than non-tinned copper but provides extended service life and field performance compared to standard bare type copper especially in wet condition installations.

These types of earth bars are commonly specified and installed in outdoor locations in the water utility, marine and offshore industries where high levels of atmospheric corrosion caused by environmental factors and moisture levels such as rain, fog and condensation necessitate improved levels of corrosion protection. Outdoor air can act as an electrolyte because it contains a variety of components which can cause corrosion of any metal.

Tinned copper handles wet conditions, high temperatures and humidity to maintain the conductive integrity of the earth bar for electrical engineering applications.

AN Wallis manufacture both standard copper and tinned copper earth bars from 6 way up to 30 way on short lead times in standard, single link or twin-disconnection link design. Image: Wallis 6 Way Earth Bar.

Applications & Necessity Of Tinned Earth Bars

Earth bars are used to provide a convenient common earthing point for electrical installations requiring an Earthing & Lightning Protection System – copper earth bars are available with single or twin disconnecting links which means the earthing bars can be isolated for electrical testing.

Tinned copper earth bars could be used in external applications or where atmospheric conditions are more severe than normal i.e. high humidity or moisture content areas and marine and offshore saline atmospheres.

Tinning protects the copper and protects the earth bars from the formation of copper oxide, tin effectively prevents oxidation.

Earth bars are a standard, efficient and convenient way of providing a common earth point with integral disconnection links permitting safe electrical isolation for testing purposes in the switchroom.

Why Should Earth Bars Be Tinned?

Tin is a soft white metal which can easily be polished, scratch brushed or flow melted to provide a bright finish.

Tin is non-toxic and is not greatly affected by the organic acids. Sulphur compounds do not readily tarnish tin and it is not impaired by either air or water but reacts with hydrochloric acid to form stannous chloride.

Tin is one of the less susceptible metals to corrosion attack consequently tin-plated surfaces of copper earth bars are adequately protected against atmospheric corrosion and hence provides longer life when exposed to corrosive atmosphere installations.

In normal state unaffected by corrosion copper is a rich brown colour – pictured below is an instance of copper oxide (“greening”) showing advanced corrosion to underground earth tapes. Tinning of the earth tapes and copper conductors prevents “greening” of the copper surface – furthermore this copper run-off can be very corrosive to galvanised steel support structures on medium/high voltage substations.

Benefits of a Tinned Earth Bar

• Tinning a copper bar protects against atmospheric corrosion providing longer life when exposed to corrosive atmospheres
• Tinning protects the earth bar against the formation of copper oxide (oxidisation)
• Tinned earth bars are an excellent solution to extend longevity and have reasonably low resistance
• Used in external/outdoors applications or where atmospheric conditions are more severe and aggressive than normal i.e. high moisture content areas, high humidity in both onshore (eg water treatment works) or offshore (oil/gas platforms)

Pictured: Here a tinned AWG 4/0 stranded copper conductor is bolted to a galvanised steel flange of a support column on a high voltage substation. Note the high pressure compression fitting installed using hydraulic crimping tools and protective paint for added protection of the copper cable lugs and conductor against corrosion in above-ground outdoor applications.

➡ T&D together with Wallis can offer a bespoke design service for custom earth bars in both tinned and standard copper construction – sizing, number of cable terminations, fixing materials and bases can be tailored to comply with specific site requirements and drawings are available on request to ensure the earthing bars are suitable.

Earth Bars

The following range of Earth Bars without disconnection links are available in both standard copper and tinned copper versions:

Earth Bars With Single Disconnection Link

The following range of Earth Bars with single disconnection links are available in both standard copper and tinned copper versions:

Earth Bars With Twin Disconnection Links

The following range of Earth Bars with twin disconnection links are available in both standard copper and tinned copper versions:

Tin Plating Services For The Electrical & Electronics Industry

The following comments have been kindly provided by Ian Molyneaux of Karas Plating Ltd – the UK’s most respected metal finishing company.

Bright Tin Plating

Tin is a silvery malleable metal that doesn’t get easily oxidized in air and is used to coat other metals to prevent corrosion. The electrical and electronics industry are heavily dependent on tin and tin alloy coatings for solderability most of which is done by electroplating. Tin plated metal is also used for food packaging giving the name to tin cans which are made mostly of steel.

Tin plating is used extensively in the electrical engineering industry to provide protection and to confer solderability. Tin electroplating is also widely used in manufacturing printed circuit boards (PCBs) and electronic components. Most electronic circuit components are made by soldering therefore the surfaces of the conductors being connected are coated in tin or a tin alloy aiding solderability. Additionally tin coating protects the components and connection from corrosion in aggressive atmospheres.

Tin is one of the easiest metals to electro deposit and one of the advantages of electroplating is that no limitation is imposed on the thickness of tin that can be applied. The required thickness can be attained by adjusting the bath parameters and time.

Tin is usually plated with a bright or matt finish. Bright tin is obtained from electroplating solutions containing brighteners, ie. organic additives causing formation of very fine grains of deposit. It has excellent cosmetic appearance.

Matt tin coatings are made in electrolytes with few grain refiners, but without brighteners. It has a dull appearance but the level of internal stresses in matt tin deposits are much less than in that of bright tin.

Bright Tin Plating

Dull Tin Plating

What is the difference between pure tin, bright tin, and matt tin?

Matt tin coatings are made in electrolytes without the addition of brighteners. Matt tin has a dull appearance, but the level of internal stresses in matt tin depositions is much lower than it is in bright tin depositions. Matt tin (in contrast to bright tin) is characterised by low whiskers growing, therefore, it is used in electronics.

Characteristics:

• a dull, semi-bright or satin-bright appearance
• disperse reflectivity
• existence of grains with an average size in the range of a few microns
• the deposit is free of the co-deposited brighteners found in bright tin plating

Dull tin is ideal for electronic or precision components. Deposits give good solder ability even after heat or steam ageing.

Karas Plating can plate onto substrates of aluminium, copper and copper clad aluminium busbars in both bright and dull tin.

Aluminium and copper clad aluminium busbar are generally used for reduction in weight and cost but both are easily tin plated

Contact Karas Plating Ltd : Call FREE today on: 0333 121 0151

AN Wallis Earthing Systems

Earthing and lightning protection manufactured by AN Wallis from high conductivity copper to BS EN 13601 is installed to protect buildings, overhead lines and medium/high voltage substations (MV-HV) against potentially catastrophic damage that can be caused by a lightning strike resulting in short circuiting of power networks.

The Wallis product range includes copper earth rods (solid copper, copper bond and stainless steel types), earth bars, earth tapes, earth clamps and aluminium tapes.

As the leading UK manufacturer of specialist Earthing and Lightning Protection Products, Wallis aims to provide the highest quality products without compromising on price or product performance in a safety critical application.

Quality assurance is integral to Wallis and to ensure this practice continues all earthing and lightning products are manufactured to stringent British and international standards.

Did You Know?

The Escondida copper mine in the Atacama Desert in Northern Chile is currently the world’s largest copper mine by reserve. The copper mine contained more than 32 million tonnes (Mt) of recoverable copper reserves at the end of 2012.

Further Reading

• Earth Tape – The Manufacture of Copper Earthing Tapes
• High Voltage Earthing & Grounding System Design Protecting Lives
• Copper Earthing Tape & Rods Protecting 33kV Substation & Transformer Bund
• Substation Earthing

Specialist Distributors: LV, MV & HV Cable Jointing, Substation & Electrical Eqpt

THORNE & DERRICK are national distributors of LV, MV & HV Cable Installation, Jointing, Duct Sealing, Earthing & Electrical Equipment – we service UK and global businesses involved in cable installations, substation, overhead line and the installation of medium/high voltage cable joints and terminations at LV, 11kV, 33kV and HV.

Contact us for 3M Electrical, ABB, Alroc, AN Wallis, CATU Electrical, Cembre, Centriforce, CMP, CSD, Elastimold, Ellis Patents, Emtelle, Euromold, Filoform , Furse, Lucy Electric & Zodion, Nexans, Pfisterer, Polypipe, Prysmian, Roxtec, Sicame, WT Henley.

Further Reading

• Tinned Copper Earthing Tapes Size: 60.41 KB