ZRC on track

Citation

(2001), "ZRC on track", Anti-Corrosion Methods and Materials, Vol. 48 No. 6. https://doi.org/10.1108/acmm.2001.12848fab.006

ZRC on track

ZRC on track

Keywords: ZRC, Galvanizing, Steel

America was built on the strength of two great transportation resources – rivers and railways. Of the two, the railroad has always held a special place in American folklore. Any mention of the Wild West never fails to raise the hide of the gust steam trains that crossed the prairies and mountains.

Today, railroads still play a critical role in the American economy. Although most of the USA's rolling stock is dedicated to hauling freight, the railroads are making a remarkable comeback in the area of passenger travel.

One of the more ambitious rail projects in recent years is the development of a high speed rail corridor between Boston, Massachusetts, and Washington, DC. The new service from Amtrak is called "Acela" – a combination of the words "acceleration" and "excellence". The new trains travel at speeds of up to 150 miles per hour (250km/hr), substantially reducing travel time between the key East Coast cities of Boston, New York, Philadelphia, Baltimore and Washington.

Prior to the initiation of the Acela train service, major renovations and upgrades were made to track and roadbeds all along the route. Tracks that carried diesel powered trains were electrified to accommodate the new Acela trains.

The most challenging section of the track electrification project was the Northend Electrification Project, the stretch between Boston and New York City. Alternately traveling through heavily urbanized areas and scenic coastal stretches, more than 200 miles of track were converted between Boston and New Haven, Connecticut (where previously electrified track begins).

This challenging project was constructed by Balfour Beatty/MEC, a joint venture of Balfour Beatty Construction and Massachusetts Electric Construction Company. Balfour Beatty was primarily responsible for engineering, while NEC handled purchasing and construction duties.

To carry the high voltage electrical wire required to power the Acela trains between Boston and New Haven, Balfour Beatty/IMC erected a series of 30-foot high galvanized steel poles, set on precast concrete foundations. A set of two poles was erected every 200 feet for the entire length of the track.

On each of these vertical poles, a two-inch galvanized pole is cantilevered out to hold the suspended electrified conductor wire. In addition, four new electrical substations were built.

As you can imagine, the requirement for galvanized steel on the project was enormous. The galvanizing was specified at 3.9 mils zinc, per ASTM A123 and A153.

There are numerous welds, fittings and bolted connections on each pole assembly, most of which required remediation work due to surface rust, cutting, grinding and CAD welds for grounding purposes. This extensive finishing work (along with field repair of damaged galvanizing) called for a powerful rust prevention coating.

After extensive testing, Balfour Beatty/MEC selected ZRC Cold Galvanizing Compound to do the job.

We understand that Balfour Beatty/MEC put a number of galvanizing coating materials to the test. When the results were in, the company's Quality Assurance department selected ZRC cold galvanizing compound as the sole specified galvanizing compound for the project. The 95 per cent zinc content of ZRC is stated to be the key to the high level of performance demonstrated in the Beatty Balfour/MEC test, and in years of proven field success. The sacrificial nature of zinc builds a protective layer of zinc salts over any damaged spot on the coated metal surface. In the manufacture's opinion no other galvanizing compound contains as high a percentage of zinc in its formulation. Other factors which reportedly contributed to ZRC's specification include the low VOC levels claimed to be present in ZRC – it reportedly meets or exceeds all USA state and federal VOC regulations – and the fact that ZRC Worldwide is an ISO 9001 registered manufacturer. The joint Balfour Beatty and Mass. Electric Construction venture is an ISO registered company, and is said to have recognized the many advantages of purchasing from a similarly qualified vendor like ZRC Worldwide.

ZRC in detail

ZRC is the brand of the highest quality zinc rich coatings on the market containing 95 per cent "ultra-pure" zinc dust by weight in the dried film. They bond to clean iron, steel or aluminium to provide maximum protection against rust and rust creepage through "galvanic action". The ZRC product lines consist of ZRC, GALVILITE, ZRC350 and ZERO VOC ZRC. ZRC Worldwide has been registered by Underwriter's Laboratories, Inc., to the International Organization for Standardization ISO 9001 Series Standards for Quality.

ZRC is widely used to prevent rust and rust creepage in place of hot-dip galvanizing, as well as the following major uses:

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  high performance base coat for a variety of topcoats;

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  repair of damaged hot-dip galvanizing, Galvalume, and zinc metallizing;

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  regalvanizing worn hot-dip galvanizing, Galvalume, and zinc metallizing;

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  repair of weldments on galvanized material; and

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  repair of damaged inorganic zinc coatings.

ZRC claims excellent long-term protection of structural steel, waste and water facilities, power plants, transmission towers and antennae, steel decking, facility maintenance and bridges. It is commonly used by original equipment manufacturers (OEMs) as in in-plant substitute for hot-dip galvanizing.

ZRC is manufactured by integrating "ultra pure" zinc dust with a trade secret organic binder. This binder allows the zinc particles to remain in contact with each other so that the ZRC is anodic to the base metal, thereby imparting true galvanic action.

In the presence of moisture, the zinc dust becomes an anode (+) and the underlying substrate a cathode (–). Corrosion attacks the zinc, leaving the base metal untouched. Zinc, being higher in the electromotive series than iron or steel, is more susceptible to corrosive attack. Thus, in the presence of an electrolyte (moisture), zinc will preferentially sacrifice itself to protect the steel. Zinc ions go into solution, liberating electrons which cause a current flow into the steel, thereby preventing ferrous ions from going into solution and beginning the electrochemical corrosion cycle. ZRC's high zinc loading (95 per cent in the dry film) and secret binder intensify this galvanic action in comparison to other brands. As a consequence ZRC-coated jobs are said to last longer saving costly labour costs associated with recoating.

According to the manufacturers, if ZRC is scratched to the bare metal, the zinc will form a hard, impervious, insoluble salt barrier on the exposed area, continuing to protect against corrosion. Essentially, the company informs us, ZRC is a self-healing film.

Initially, the protection provided by ZRC is wholly that of anodic action. As the zinc is sacrificed, zinc hydroxy carbonates and other zinc salts form in the film, making the coating denser and reducing its conductivity. Thus, the anodic action continues until the film is converted into a dense, impervious, cementious coating. The coating will reportedly now function as an impermeable barrier resistant to weather, water and fume attack.

Although ZRC is commonly applied like a paint (brush, roller, aerosol, compressor type or airless sprayer) it is unlike any type of paint because it provides galvanic action and will not allow any rust creepage.

Although ZRC does not require any top-coat for the purpose of corrosion protection, several determining factors may deem it advisable. Specifically these factors include environmental service conditions (salt water, acidic (ph < 6.5), alkalinity (ph > 10.5) chemical fume, etc.) the availability of future ongoing maintenance, and aesthetics. However, if determining factors should deem it advisable ZRC can be top-coated.

Details available from: ZRC. Tel: +1 800 831 3275.