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#20-21 Update of Protective coatings for steel bridges and release of new specifications for coating steel structures and anti-graffiti coatings

Published: | Category: Technical advice note | Audiences: Road traffic engineers & consultants, Roading contractors

This note is to advise suppliers, specifiers and applicators for structural steelwork and protective coatings that the following are now available for commonly used coatings systems.

Purpose

This note is to advise suppliers, specifiers and applicators for structural steelwork and protective coatings that the following are now available for commonly used coatings systems:

  • updated Protective coatings for steel bridges guide
  • new NZTA S9 Specification for coating steelwork on highway structures
  • new NZTA S10 Specification for anti-graffiti coatings.

The new specifications will be available to be used in contracts from the date of this notice.

General information

Protective coatings for steel bridges has been revised to align with the new NZ durability specification, SNZ TS 3404, and in response to user feedback.

The new NZTA S9 Specification for coating steelwork on highway structures has been prepared to complement AS/NZS 2312 and the quality requirements in the revised NZ steel fabrication standard AS/NZS 5131 and includes model inspection test plans for the different protective coating systems. 

NZTA S10 Specification for anti-graffiti coatings is based on the new Austroads specification ATS5820 for anti-graffiti (AG) coatings and sets out the requirements for product approval, supply and application to highway structures. It replaces the Auckland Motorway Alliance (AMA) list of approved products which has been withdrawn.

The processes and procedures outlined in this update must be followed by Waka Kotahi for all relevant contracts undertaken from now on.

Purpose of the notice

The purpose of Protective coatings for steel bridges is to optimise the long-term capital and maintenance costs of steel structures through the implementation of best practice in the selection, application and maintenance of protective coatings on steel structures.

The guide generally provides an overview of the key processes and considerations with references to other key standards and documents. It is provided to inform and assist the wider industry in achieving best practice.

S9 Specification for coating steelwork on highway structures is a prescriptive materials specification for coatings systems. It is broken down into three parts, reflecting the three parts of the parent standard AS/NZS 2312 and aligns with the latest guidance given in AS/NZS 5131. These parts are:

  • inorganic and organic paint coatings
  • zinc galvanizing and duplex coating of galvanizing
  • thermal metal sprays (TMS – zinc and aluminium) and duplex coating of TMSs.

S10 Specification for anti-graffiti coatings specifies the requirements for the supply and application of anti-graffiti coating systems to structures, roadside furniture and traffic controller boxes. The specification is based on Austroads technical specification ATS 5820 Anti-graffiti coatings. The specification details permanent (non-sacrificial) coatings that are used on steelwork and sacrificial coatings that are used mostly on concrete and can be used on steelwork.

Changes

Protective coatings for steel bridges has been amended and updated. It now includes details for recommended test coupons, an updated net present value (NPV) example for coating selection, advice for treatment of the top flange under a composite deck, an updated commentary on weathering steel issues and advice on the prevention of base-plate corrosion.

NZTA S9 is the first in a proposed series new standard coating specifications. It is expected that this will simplify project specification writing and also introduce a “level playing field” that will also allow for more competitive pricing from applicators by adoption of standard requirements.

NZTA S10 is also a new standard specification and sets out the test and certification requirements for both sacrificial and non-sacrificial AG coatings. Application of AG coatings to steel structures is specified in NZTA S9.

Communication plan

The  target audience for these documents is generally experts involved in the design, specification, construction and maintenance of highway structures, in particular those constructed of steel. Advice of these changes will be promulgated by:

  • This note advising the release of these new documents;
  • Direct access via the website and intranet; and
  • Appropriate industry presentations.

Implementation

Protective coatings for steel bridges and specifications NZTA S9:2020 and NZTA S10:2020 can be implemented immediately for use with new designs, and on existing contracts by negotiation, where required.

The documents are available on the Waka Kotahi website for download.

Document review

The review of Protective coatings for steel bridges was undertaken in response to industry feedback and updated standards. Specifications S9 and S10 were developed in conjunction with designers, specifiers, fabricators and coatings specialists. It is anticipated that ongoing review of the documents will be undertaken in a similar manner. Feedback will be welcomed.

Publication details

Document: Protective coatings for steel bridges: A guide for bridge and maintenance engineers
Author: Waka Kotahi New Zealand Transport Agency
Published: August 2020
ISBN: 978-0-478-41922-1 (online)
Version: 1.2
Found at: https://www.nzta.govt.nz/resources/protective-coatings-steel-bridges/

Document: NZTA S9 Specification for coating steelwork on highway structures
Author: Waka Kotahi New Zealand Transport Agency
Published: October 2020
Version: 1.0
Found at: https://www.nzta.govt.nz/resources/specification-for-coating-steelwork-on-highway-structures

Document: NZTA S10 Specification for anti-graffiti coatings
Author: Waka Kotahi New Zealand Transport Agency
Published: October 2020
Version: 1.0
Found at: https://www.nzta.govt.nz/resources/specification-for-anti-graffiti-coatings/

Further information

If you have any questions or feedback, please contact the Lead Advisor at bridgemanual@nzta.govt.nz

 

[signed]

David Darwin - Chair, Ratification Group

Vanessa Browne - Delegated Approver

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