Corrosion Protection and Conservation

Rowan Technologies has a wealth of experience in the protection and conservation of both historic and modern buildings both in the UK and further afield. We are advisers to English Heritage and have been involved in the conservation of many of the UK's most prominent historic buildings.

Cathodic Protection

Cathodic protection (CP) is a method of controlling corrosion in metals embedded in stone, concrete and masonry by suppressing the electrochemical corrosion reaction. One of the advantages of CP is that it can provide protection without changing the immediate physical environment of the structure. By its nature, CP provides the optimum electrochemical conditions for the material being protected, thus preserving the visual appearance of the structure.

Rowan Technologies are experts in CP systems, having installed and maintained systems on a large number of prominent historic buildings and structures around the UK. We can provide custom designed systems for virtually any application, from the smallest monument to the largest cathedral.

We can also supply systems for more modern buildings as well as refurbish and recommission the electronics of third-party CP installations.

Concrete

Rowan Technologies have extensive experience of both historic and modern concrete structures. We offer a comprehensive concrete inspection and consultancy service ranging from testing carbonation depths to preparing and costing repair and conservation strategies.

Metal Roofs

With extensive experience of both contemporary and historic structures, Rowan Technologies provides a comprehensive specification, monitoring and inspection service for all types of metallic roofs (lead, stainless steel and copper). During collaborative research projects with English Heritage, a chalk-rich coating (patination cream) supplied by us has been developed for protecting the underside of lead roofs from corrosion.

Cathodic Protection

The corrosion of embedded metalwork is becoming an increasing problem in our historic buildings and monuments. Even if the rate of corrosion is relatively low, in the long term it results in the fracturing of the surrounding stones and in severe cases the loss of structural integrity. This is due to the incredible expansion forces created by corrosion; the volume ratio between iron and rust can be as high as 1:7.

Architects have, in the past, attempted to remove as much of the original iron fittings as possible and replace them with more corrosion resistant materials. The conservation policy now followed in the UK for heritage buildings is that of minimum intervention with the intention of retaining as much of the original structure as possible.

Cathodic protection (CP) is a non-destructive method of controlling the corrosion of iron and steel embedded in stone, masonry, brick or concrete. It is the application of a small negative charge to the embedded metalwork, and is being used increasingly to control corrosion within historic structures and buildings.

There are two types of CP system:

Impressed Current Cathodic Protection (ICCP)

ICCP systems require an external power supply, normally using mains powered electronics to provide the DC current to the iron or steel to be protected. The schematic below illustrates the principles as applied to iron cramps embedded in stonework.
Schematic for ICCP

Sacrificial Anode Cathodic Protection (SACP)

SACP systems use a sacrificial anode (a large piece of zinc or magnesium buried in the ground) which corrodes preferentially to the embedded metalwork. The sacrificial anode is placed in close proximity to the corroding metalwork and is electrically connected to it. As the sacrificial anode corrodes, it generates a current that passes through the building material to provide protection to the embedded metalwork.
Schematic for SACP

One of CP’s main advantages is that it provides corrosion control without changing the immediate physical environment; there may still be now, or in the future, damp stone, masonry or concrete adjacent to the metal which would previously have allowed corrosion to continue. Cathodic protection provides the electrochemical conditions to control this corrosion process.

The application of cathodic protection to historic structures is now becoming widely accepted as the process is fully reversible, cost effective and is in accordance with modern day conservation principles. Rowan Technologies are experts in the application of cathodic protection to historic buildings and monuments, and have installations in many well-known and listed structures.

We also supply systems for more modern buildings as well as refurbish the electronics of third-party CP installations. A recent example is the refurbishment and recommissioining of the ICCP system at St. Andrews House, Edinburgh, the working offices of the Scottish Government (see Further Reading, below).

Concrete

Reinforced concrete was first used in the construction industry in the late 19th Century. Concrete is very strong in compression but relatively weak in tension. Steel reinforcements were therefore added to overcome this limitation. The reinforcements may consist of steel bars, meshes, rods and wires.

Most early reinforced concrete structures now require some form of repair and conservation. The majority of damage that occurs to reinforced concrete structures is due to corrosion of the embedded steel reinforcements. As the steel corrodes, it can expand by up to a factor of 7, damaging the surrounding concrete.

Before any repair or conservation plans can be formulated, it is essential that a comprehensive concrete assessment is carried out in order to fully understand the nature of the damage and the causes of deterioration. Rowan Technologies are specialists in concrete assessment, having inspected and reported on many historic and modern concrete structures.

Rowan Technologies’ concrete assessment services include:

  • Full defect mapping
  • Embedded metal survey
  • Concrete strength testing
  • Core sampling and carbonation testing
  • Electrochemical potential and corrosion rate (LPRM) testing
  • Chemical analysis
  • Cover meter analysis
  • Render analysis
  • Conservation and repair strategies, work scopes and costings

Metal Roofs

Rowan Technologies has many years experience of metal roof inspection, specification and recommendation relating to long-term materials performance (corrosion, deterioration and cracking). The company undertakes environmental monitoring to determine periods and causes of condensation within roofs. We provide consultancy services for all types of metal roofs and we have a long-standing working relationship with English Heritage.

We have worked on many famous historic and modern roofs, including the large lead roofs at the Tower of London and the modern ventilated stainless steel roofs at Liverpool’s Metropolitan Cathedral, in addition to numerous historic houses and churches.

A five-year research project, working with English Heritage, on the corrosion of the underside of lead, has resulted in the development of a chalk-enriched emulsion (Patination Cream) which Rowan Technologies now supplies.

Chalk Enhanced Patination Cream

Rowan Technologies supplies a chalk-rich corrosion protection coating (Chalk Emulsion or Patination Cream) for the underside of lead roofing. This product was developed in collaboration with English Heritage and uses high-quality ICI/Dulux emulsion coatings. Extensively tested at a number of sites, it has been evaluated under severe corrosion conditions for over ten years.

The chalk systems were originally developed for traditional non-ventilated roofs where corrosion has previously been found or where the risk of corrosion occurring is significant. It is also applicable to modern roofs where lead may be laid over man-made boards that have the potential to emit carboxylic acids if they become damp.

The chalk emulsion is available in 5 litre containers. The coverage rate is between 22 to 26m² per container for a single layer. Orders can be placed by contacting Rowan Technologies directly.