Zinoco

For corrosive rail environments like coastal track, wet tunnels, level crossings and stray current environments, Zinoco^® ensures maximum rail life.

With superior durability and corrosion protection in use our industry award-winning Zinoco is simple to install and maintain, delivering improved safety and availability of rail networks.

Protection in harsh conditions

British Steel has a long history of providing solutions to customer issues. Our Zinoco coated rail is an example that provides corrosion protection to rails in harsh corrosive conditions. Locations that typically give rise to corrosion issues are:

• Level crossing / railroad crossing / grade crossing
• Tunnel / Underpass / Overbridge
• Coastal routes
• Sabkhas (salt pans)
• Third rail stray current locations

Corrosive environments can reduce rail life vastly, with unprotected rail lifetimes below six months being reported in some instances. Whilst loss of rail section due to corrosion can occur generally or in more localised areas (e.g. around rail fastenings) it is also important to note that foot fatigue failures often occur as a result of foot corrosion. Corrosion pits (often unseen) on the bottom of the rail can initiate fatigue cracks which can then grow undetected, resulting in rail failure.

The corrosion protection performance of Zinoco coated rail has been validated in both laboratory tests and track tests with Network Rail, SNCF and RATP. 

Sacrificial (cathodic) protection for damage tolerance

Most rail coatings provide a barrier to corrosion by preventing air, water and salts from coming into contact with the steel rail. 

Zinoco provides an excellent barrier to corrosion with greatly enhanced impact resistance compared to previous coatings, but it also has a key second method of defence by providing sacrificial protection, even if areas of the coating have been breached. This is how it works: 

• The Zinoco rail outer coating becomes a sacrificial anode
• The steel being protected (the rail) is the cathode
• Electrons flow from the Zinoco to the rail
• Zinoco oxidises in favour of the rail
• Corrosion of the rail steel core is prevented

Cathodic protection is used to provide robust corrosion resistance to many high value and safety critical assets such as pipelines, oil rigs and ships hulls.

When Zinoco rails are in contact in an electrolyte e.g. salt water, differences in electrical potential develop between the Zinoco and the steel core of the rail and an electrolytic cell is formed. The Zinoco outer coating is more electrochemically active than steel.

As a result of the differences in electrical potential, negatively charged electrons flow from the Zinoco (anode) to the steel rail (cathode) and Zinoco in the anode area is converted to positively charged ions.

At any areas of coating damage, the steel cathode surface becomes negatively charged with electrons reacting with positively charged hydrogen ions from the electrolyte, liberating hydrogen gas. There is no chemical reaction between the steel cathode and the electrolyte and therefore the steel is protected from corrosion. In simple terms - the coating sacrifices itself over time to protect the steel beneath. 

The unique durability and real-life performance of Zinoco mean that long length deliveries of corrosion protected rail are possible. Longer length availability mean that longer lengths of corrosion prone track such as wet tunnels and coastal routes can be protected with minimised installation time and significantly reduced on-site welding requirements. In this recent example over 50 site welds were avoided by supply of 216m protected rails into a wet tunnel environment. 

See our first 108m Zinoco rails on their way to a UK tunnel installation in the video clip below. 

Zinoco^® is a registered trademark of British Steel