Technical Presentations at the April 2009 Meeting

1.1  ‘Corrosion Testing in Support of Marine Applications’, Robin Oakley, QinetiQ 

The marine corrosion environment includes conditions of seawater immersion, atmospheric exposure and also the biological influences of fouling micro- and macro-organisms. The corrosion engineering problems faced in these environments need to be answered through the correct use of effective corrosion test methods.  

To this end, the methods, benefits and weaknesses of marine seawater immersion and atmospheric exposure trials were explored, alongside a discussion of the use of seawater system test rigs and flow loops. These long term tests were compared with accelerated laboratory test methods, such as salt spray cabinets, erosion-corrosion techniques and electrochemical procedures. The particular problems associated with correlating atmospheric exposure results with accelerated salt spray-type tests for steel coated with metallic and non-metallic coatings were described. 

Areas for future development in marine corrosion testing were proposed, covering rapid assessment of marine paint coatings and the evaluation of the performance of fouling-release coatings.

3.1  Keynote:  'Corrosion Resistant Alloys for Oil & Gas Engineering Applications', John Grubb, ATI-Allegheny Ludlum

 This presentation covered the following areas:

•         Brief Overview of ATI (Allegheny Technologies Incorporated) and ATI Allegheny Ludlum

–        Organization & Business Sectors

–        Locations

–        Products

–        Market Sector Teams

•         Overview of Materials used in Oil & Gas production

–        Different Products for Different Jobs

–        Offshore: Topside & Subsea

•         Review of the Corrosive Character of Seawater

–        PRE and PREN

–        Corrosion Testing and Ranking of Alloys

–        SCC

•         Future Trends: Materials in the Arctic

Standards and Information Sources

[ATI-Allegheny Ludlum, Technical and Commercial Center, Brackenridge, PA 15014-1597, (724) 226-6230, jgrubb@alleghenyludlum.com]

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3.2   ‘CP on Offshore Wind Farms’, Ross Fielding, Impalloy

The Presentation provided an introduction into the history and capabilities of Impalloy Limited.  Manufacturing processes of various types of Sacrificial Anodes utilised in the Marine, Industrial and Offshore Markets was briefly covered in the initial section of the presentation; anode types discussed included: 

  • ·        Marine Flush mounted Anodes

  • ·        Stand Off anodes for Platforms & Harbours

  • ·        Bracelet anodes for Submarine Pipelines

The main section of the presentation gave an insight into constructional methods and types of foundations for wind turbines currently in use offshore and to also provide a current status overview on corrosion control systems afforded to offshore wind farm foundations. 

Constructional methods and types of foundations for offshore wind turbines were presented and discussed, those being: 

  • ·        Steel Mono-Piles/ Transition Pieces

  • ·        Traditional Fixed Steel Platforms

  • ·        Concrete Foundations

  • ·        Tethered Steel Towers

Basic design considerations and specific international codes and standards utilised when designing CP systems for foundations were highlighted including ISO and DNV standards.  Component parts and monitoring activities for both SACP and ICCP systems were researched and discussed. Monitoring on SACP systems relies on portable reference cells, whilst ICCP employs structure mounted reference electrodes. 

The majority of CP systems for offshore wind farms employ sacrificial anodes, probably due to low maintenance issues and ease of installation and operation.  Generally coatings are only used down to about one metre below Lowest Astronomical Tide, from there to the toe level of the structure is bare steel and relies on CP.  Current practices for anode layout and structure mounting methods may need to be re-assessed on monopile foundations in deeper water. 

[Contact: Ross Fielding, Impalloy Limited, Wilenhall Lane, Bloxwich, Walsall WS3 2XN] 

3.3    ‘Erosion Corrosion Performance and Prediction for Marine Alloys’, Xinming Hu and Anne Neville, University of Leeds 

It is well known that the industries that transport slurries and other particle-laden liquids in pipes or seawater propulsion systems such as offshore and marine technologies spend millions of pounds every year to repair material damage. The typical examples of this kind of material destruction are erosion-corrosion damage to pumps, impellers, propellers, valves, heat exchanger tubes and other fluid handling equipment. In a recent survey erosion-corrosion was rated in the top five most prevalent forms of corrosion damage in the oil and gas industry. A lot of work has been carried out to characterise and classify the materials related to mining and marine industries. 

Erosion-corrosion in aqueous systems is dominated by two major mechanisms: electrochemical corrosion and mechanical erosion. On account of the greater material loss than the sum of their individual components, the interaction between electrochemical and mechanical processes has been recognised and referred to as  ‘Synergistic’ or ‘Additive’ effects. 

Numerous studies have focused on assessing material durability in erosion-corrosion environments as a function of several parameters including velocity, sand loading, temperature or pH. Though the studies show how the environmental factors affect erosion-corrosion behaviour, it has been difficult to predict quantitatively how the damage will be affected by factors and their interactions. In an attempt to extend understanding of how factors affect the extent of damage in erosion-corrosion and constitution of that damage (i.e. corrosion, erosion or synergy), and experimental design method has been used. 

In this study a full two-level factorial experimental design method is presented, which was applied to study the individual effects of each parameter and their interactive contributions to the overall material degradation as well as its the components. The experimental design analysis, the correlation between the material hardness and the test results enable the detailed understanding of the erosion-corrosion performance of the materials to be made. With such knowledge further improvements in the cost-effective use of materials and in the development of accurate prediction tools will be made. 

[School of Mechanical Engineering, University of Leeds, LS2 9JT, Leeds, UK.  X.Hu@leeds.ac.uk, A.neville@leeds.ac.uk]

3.4  ‘A Material Specification Rationalisation Process’, Ian Hamilton, Aker Solutions

 The Pre-Existing Issues were felt to be: 

  •       Document (Header) does not indicate ‘ownership’.

  •       Document title inadequately identifies content.

  •       Contents are ‘fixed’ (new document required to accommodate – particularly customer orientated - change(s)). Consequently multiple documents exist for the same alloy designation.

  •       Reference to sub-tier specifications requires Supplier to hold multiple documents in order to process each order.

  •       No common layout – material specifications have varied construction.

  •       Storage of previous revisions not adequately controlled. 

A core group was created to consider these pre-existing issues, resulting in the Rationalisation: 

A simultaneous two-prong solution approach evolved: 

1.            Document storage / retrieval

2.            Document content / layout 

The finished document had various advantages / changes when compared to the original style: 

3.            Comments / Comparison  

  •        Clearly displayed ‘ownership’.

  •        Fully detailed title for easy recognition / selection.

  •        Simple access to all previous revisions.

  •        ‘Flexible’ format – allows for specific customer requirements.

  •        Only one document per specification designation – thus replacing numerous documents.

  •        Self-contained document – no sub-tier reference, thus reducing paperwork held by Supplier.

  •        Layout used as a format / template for other specification documents.

  •        Consistent style / layout independent of alloy requirements.

  •        Potential to reduce costs by standardising testing requirement.

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