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If your particular query is not answered in this section
or any other area, please contact
one of our staff who would be pleased to assist.
Does NJM operate only in East Anglia?
No. Although originated and strongly based in East Anglia, and now Nuttall’s office for the East of England, NJM, because primarily of its specialist expertise, delivers projects throughout UK and when required, abroad.
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How big is Nuttall John Martin?
NJM is one of the largest civil engineering companies in East Anglia, which is a subsidiary of the Nuttall family. Between Nuttall and the NJM there is a capability of providing a full range of civil engineering and infrastructure.
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How do I go about starting a career with NJM?
There are a number of ways to start a career with NJM; either
Send an email expressing interest to malcolm.mcallister@jmcl.co.uk
Phone our office in Shipdam and request further information. Tel 01362 822212
Visit our Parent company website www.edmund-nuttal.co.uk
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Isn’t NJM a marine contractor?
Yes, but not exclusively, of a turnover of £38m in 2005, 70% was generated by its other activities on roads, rail and infrastructure.
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Who are Nuttall?
Edmund Nuttall Ltd is one of the UK leading civil engineering and infrastructure maintenance contractors. Nuttall is part of the European construction group “Royal BAM” which has the experience, resources and expertise to under take projects of any size in the UK and overseas.
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Does all ALWC look the same?
No, when inspecting for attack, keep your eyes open. There are cases of concentrated corrosion which do not follow the classic pattern. Although you will probably find that most cases do.
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Does ALWC occur on steel structures in coastal waters throughout the world?
No reason has been found why it should not occur, but while reports are widespread regardless of geography, there are nevertheless insufficient reports to state this categorically.
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Does Cathodic Protection always protect against ALWC?
Yes, provided the correct potential difference is established on all parts of the steel under attack. On sheet piles, sacrificial (galvanic) electrodes fixed to every other pair of piles might not achieve an even current density across the entire section on plan. Impressed current systems need similar careful design to achieve an economic solution.
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How can I find someone to inspect my structure?
Follow the link to contacts or call-back.
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Is ALWC found in fresh as well as salt water?
Yes, but because of the lower conductivity in fresh water the effect is ot as severe.
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Is there a solution to ALWC?
Research carried out throughout the world has shown that ALWC can be prevented by the use of Cathodic Protection (CP). It has also been shown that CP can halt attack.
However, the choice of repairs or preventative installations will be affected by the layout and use of the structure. In a badly affected structure there will probably be the need for remedial measures for structural or usage purposes in addition to the consideration of the ‘killing’ of corrosion cells.
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What is ALWC
Accelerated Low Water Corrosion. It has been variously defined as ‘a particularly aggressive and localised form of low water corrosion which can occur in tidal and brackish waters on steel maritime structures’. and as ‘the localized and aggressive corrosion phenomenon that typically occurs at or below low-water level and is associated with microbially induced corrosion’. from which it can be seen that it is difficult to establish the crucial fundamentals, which are shown in more detail in this definition ‘ALWC occurs at a rate up to an order of magnitude greater than normal seawater corrosion. The attack is localised, and of a pitting or selective nature. A classic form is limited to a horizontal band 600mm high around low water although it can be found occasionally, in discrete patches, extending down to bed level. It generally has a recognisable appearance and characteristics, revealing clean corroding steel under lightly adherent orange and black corrosion products’.
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What is the primary cause of ALWC?
ALWC is a microbially influenced corrosion (MIC) relying on a consortium of both aerobic (Sulphide Oxidising Bacteria -SOB), and anaerobic (Sulphate Reducing Bacteria -SRB).
There is a symbiotic relationship between the bacteria and the electrochemical corrosion environment at the steel face, which allows both to thrive at the expense of the steel structure.
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Are limpet dams only used on sheet piles?
By no means. We have dams for tubular piles of all sorts and sizes as well as for repair of lock gates and in one case sliding clamps on pontoon retention system. You can see some of these applications in our case histories.
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Is a Limpet Dam your invention? Do you hold a Patent?
No and Yes. The principle of a dam has been around for centuries, mostly used on ships’ hulls, probably by the Romans, and certainly on Henry VIII’s fleet. However, the features of a dam, particularly to make a seal against a variety of shapes, a requirement for work with all forms of sheet pile, is novel.
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What is our biggest dam?
Limpet dams vary in size width, hieght and depth. A recent repair of ship damage to a major container quay was 19m deep with a capacity of a 40-seater coach. The variations include our ‘pencil’ and ‘pregnant’ dam designs.
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