A collection of recently edited and up-dated technical guidance documents from the CED Coatings group has recently been published in the member’s area of the Institute of Corrosion website. Each document includes extensive referencing to relevant standards and other sources of information. A summary of these documents is presented here. Please note that to access the members area you will need to register or re-register by filling in the on-line form at https://www.icorr.org/members-area.
CED/CT01 Inspection and testing – Surface preparation and organic coating-related inspections
This document discusses the purpose of inspection, the specific areas that a paint inspector might check, the relevant standards and methodologies, the reasons behind the various requirements, and the equipment used. Subject areas include: pre-coating (visual inspection, surface profile checks, extraction of soluble salts, surface cleanliness checks, ambient monitoring) and post-coating (coating thickness checks, adhesion testing, holiday detection). The focus is on those methods which are considered the best, or most commonly used, but an emerging test for post-coating corrosion protection monitoring, namely electrochemical noise measurement, is included as an Appendix.
CED/CT02 Surface Preparation Methods
CT2 provides an insight into the types of preparation methods that are available, the equipment used and how this is related to industry standards. The three common surface preparation methods, i.e. abrasive blasting, hand and power tool, and water jetting, are discussed, with particular attention given to water jetting, which is less well-known than the others. The advantages and disadvantages of each method are also highlighted.
CED/CT03 Organic coating application methods
This document provides an insight into the available coating application methods and the equipment used. The various application methods described are: brush application, roller application, spray application (including air-, airless-, HPLV-spraying, auto-deposition, and rotating discs and bells), dip coating and flow coating.
CED/CT04 Paint: a definition and generic organic coating types
This document provides an insight into the generic organic coating types that are available, highlighting the types and compositions of the coatings. It begins with a brief definition of what comprises a paint system and an outline of why, when and where anticorrosive paint is used. It provides definitions of resins (e.g. alkyd, epoxy, polyurethane/acrylic urethane, vinyl esters, and silicone-based resin systems), pigments and extenders, solvents, additives (driers, thixotropes, UV absorbers, de-foamers, wetting agents). Some examples of complete paint systems (primer, stripe coat, intermediate coat or coats, and finish coat) are also given.
CED/CT05 TMS: Thermal metal spray
CT05 defines the technique of thermal metal spraying, placing it in context and noting the relevant surface preparation standards. The methodology is then described in detail, including flame spray and arc spray. Properties such as abrasion resistance, galvanic protection, longevity and the permeability of thermal metal spray to water are discussed. This is followed by a section covering the appropriate uses of TMS, as well as noting where it is NOT recommended.
CED/CT06 On-site and off-site application of intumescent fire and corrosion protection coatings for steel structures
This document provides a definition of intumescent coatings and highlights the key issues concerning specification and use of the types of coating appropriate in particular contexts. It also covers, certification, development and handling of the coating, and preparation of the substrate surface, together with the advantages and disadvantages of off-site or on-site application.
An emphasis on the corrosion protection aspects of the intumescent system, and information on the types of system that will be effective in this context, are included in the sub-section on environment. A large number of sources of further information are included towards the end.
The 2018 CED working day meeting will be held at the Birchwood Park Conference Centre, Warrington, on Tuesday 24 April 2018 on the subject of ‘Atmospheric Corrosion in Industrial Applications’. An information and registration leaflet is included in this issue of Corrosion Management. Exhibition space will be available for hire.
The Coatings Working group has prepared a series of guidance documents on the following topics:
• Inspection and testing of coatings
• Organic coating application methods
• Surface Preparation methods for coating application
• Paint: a definition and generic organic coating types
• Thermal metal spray coatings
• On-site and off-site application of intumescent fire and
corrosion protection coatings for steel structures
These documents are now available through the members’ area of the Institute’s web site. If you have any comments on them please send them to firstname.lastname@example.org
A CED Working day and Symposium on Corrosion Engineering and Concrete was held on Thursday, 27 April at IMechE Engineering Training Centre, Sheffield. The meeting was sponsored by the Institute of Concrete Technology. Some sixty delegates were welcomed by the Chair of CED, Nick Smart (Amec Foster Wheeler), who introduced the Division for the benefit of those who were not members and also outlined the programme for the day. This was followed by an ‘Introduction to the Institute of Concrete Technology’, given by the President, Raman Mangabhai.
Chris Atkins (Mott MacDonald) addressed, ‘The trouble with concrete’. He outlined the origin of the problems with concrete caused by shrinkage and the means of overcoming its poor compressive strength by inserting reinforcement. Settlement cracking was capable of giving rise to 2 mm wide cracks, which could penetrate right up to the rebar. Other aspects of steel corrosion in concrete were then discussed including the electrochemical mechanisms of corrosion, forms of chemical attack that can occur during use, repairing chloride-induced corrosion, cathodic protection, and decisions to repair (covered by BS EN 1504), with BS EN ISO 12696 providing further guidance on conformity.
Next, David Simmons (BAM Nuttall) outlined, ‘The use of coatings to manage corrosion in concrete’. “Getting it right first time” is a phrase that is often used in construction. This applies equally to reinforced concrete if it is to be durable and provide the service life as specified by the end-user. The problem with reinforced concrete is that while engineers fully appreciate the importance of including the reinforcing steel, not much consideration is given to the low-cost, easy-to-use, void filling material that surrounds it. In effect, the concrete cover should be regarded as a protective coating, and must be properly specified, batched and used, which can only be achieved by proper exchange of information between the designer, user, and producer of the concrete.
‘Impressed current cathodic prevention of steel in concrete’ was the subject of the lecture by Hugue Bois (SAPIEM SA, France). Theoretically, steel in concrete should not experience corrosion. The concrete pH is around 13 and this alkaline environment stabilises the iron oxide or hydroxide film, thereby passivating the embedded steel. The concrete layer also presents a low permeability barrier vs. external aggressive species, e.g. chloride ions or carbon dioxide. However, in some cases, ingress of these species reduces the pH to 8 or 9, thus impairing the passive film. Examples of field experience were given, including reinforced concrete steel piles, the use of Mn/MnO2 reference electrodes, and the importance of identifying the various at-risk zones, for example of a sea wall, viz. immersed wall, buried wall, atmospheric, splash and tidal zones.
The final presentation entitled, ‘Latest understanding of the corrosion of Magnox, aluminium and uranium metal wastes in cement’ was given by Hugh Godfrey (National Nuclear Laboratory). An overview of the work that has been carried out in the nuclear industry on the corrosion of Magnox (magnesium/aluminium alloy), uranium and aluminium wastes encapsulated in cements was presented under the following headings: the origin of the waste; how the waste is encapsulated in cement; how the corrosion rates were measured and a comparison of the corrosion behaviour of the three metals. Uranium has the simplest corrosion behaviour – an initial incubation period followed by continuous corrosion and a steady rate. Magnox behaviour is more complex, with the corrosion rate gradually decreasing to a fixed long-term rate. This contrasts with the corrosion rate for aluminium which continually decreases without appearing to reach a steady rate.
The technical talks from this meeting are available (in pdf form) on the members area of the ICorr website.
After the presentations, the delegates were afforded the opportunity of visiting the concrete and corrosion laboratories at Sheffield Hallam University, and to participate in CED Working Group Meetings. The concrete and CP, nuclear and coatings work groups all had successful sessions.