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Corrocoat products provide engineering structures and equipment with long-term and cost-effective protection against corrosion.
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We’ve all heard of the term pitting corrosion. But what does this mean and where exactly does it occur? Here we go in to further detail to provide the answers to the questions and also explore ways to repair and protect badly pitted steel.
“Pitting Corrosion” is the formation of holes in an otherwise relatively un-attacked surface. It is a form of localised corrosion that proceeds because of local cell action which produces cavities beginning at the surface. The cavities may or may not become filled with corrosion products. Corrosion products may form “caps” over the pit cavities which are described as “nodules” or “tubercules”. While the shapes of pits vary widely, they are usually rough saucer shaped, conical or hemispherical.
Pitting corrosion is quite common. It can occur on a metal surface because of localised differences in composition or surface contamination, deposition or incorporation of metallic and non-metallic particles, or contact with dissimilar metal. This type of attack can by caused by a break in a protective film on the metal surface, such as an inhibitor film, oxide film or break in coating. It also may be caused by the uneven deposition of solids (metallic salts) which in themselves create a local action because of the potential difference between the salts and metal surface. An example is ferric sulphate.
The Corrocoat Corrofill range consists of fillers for badly pitted steel, in application, which require a high performance, chemically resistant coating system.
One of our specialist corrosion protection coatings would then be applied to complete the process.
A two-pack organic peroxide, catalysed bis phenol ‘A’ polyester filler or grout.
A general-purpose two or three pack epoxy filler, grout and repair compound.
A two-pack, vinyl ester filler and grouting material containing abrasion resistant fillers.
Contact us to find out more on how we can repair and protect corrosion pitted steel and other pieces of equipment or machinery, suffering from other types of corrosion.
Biofoul is our heavy duty, anti-foul coating, developed to provide optimum protection in both sea water and fresh water environments where biofouling and marine growth are evident. Biofoul contains no chemical agents and relies on its performance for a unique blend of metallic copper pigmentation and flakes. It can, therefore be considered non-toxic.
Years ago, mariners coated their wooden vessels with copper sheeting to provide excellent anti-foul properties. Biofoul works in exactly the same way, presenting a copper rich surface to the fouling agents.
Unlike many anti-foul materials, Biofoul forms a hard and durable surface, resistant to scuffing and high velocity water flow. This makes it ideally suitable for use on static constructions as well as pipework and other areas where flow velocity may be a consideration.
One typical area of use is sea water intakes, where marine growth can substantially reduce the inlet size, reducing flow and involving high maintenance levels and cost. Other areas, such as marine piling and support structures, vessel hulls and pontoons also benefit from the long-term protection properties of this product.
The material is a three-pack synthetic, hydrolysable polyester solution designed for application over a corrosion barrier coating – typically Corrocoat’s own Polyglass materials. The product is easily applied using airless spray equipment and has quick dry and curing characteristics.
As an anti-foul, Biofoul provides an excellent alternative to toxic fouling materials, including electrolysis processes, which produce unwanted levels of chlorine which can also cause serious corrosion problems. Biofoul has been tested in an independent laboratory for both effectiveness and non-toxicity.
When first applied, Biofoul is a copper/gold colour. The colour changes with age to the pleasantly green appearance of oxidised copper. This characteristic allows Biofoul to be used not only for anti- fouling purposes, but also for decorative and architectural use on building features such as domes and spires.
View the Biofoul data sheet here.
With a strong working knowledge and expertise in management and engineering, Nigel joined Corrocoat as the Engineering Foreman in 1990. Progressing to the Works Director in 2005, Nigel has made a huge impact and contribution, leading the site operations and engineering team to deliver outstanding results. Nigel has been instrumental in strengthening the engineering team in recent years, encouraging a culture of continuous development and performance improvements, through a number of progressive workplace initiatives. He also works closely with our Pumps Manager, Research and Development division and other areas of the business to ensure the service we offer continues to excel.
Nigel said: “I’d like to take this opportunity to say it has been a privilege to be part of such a fantastic business. I wish the company and the wonderful team, both here in the UK and our partners overseas the very best for the future and have no doubt, the business offering, service and reputation as world leading corrosion specialists will continue to thrive.”
In the lead up to his retirement, Daniel Briggs worked alongside Nigel, in his new role as Works Manager, to ensure a smooth transition in to the duties and responsibilities of managing and overseeing all areas of operations going forward. Daniel has been part of the team here at Corrocoat UK for over 7 years, in technical sales and estimating. He has fantastic working and industry knowledge, and has built and sustained excellent working relationships throughout the company and with clients.
We’d like to take this opportunity to thank Nigel for the past 30+ years – wishing him all the best in his retirement, and also congratulate Dan on his new role.
BHM Engg Services PTE Ltd are our exclusive distributors and specialist applicators in Singapore. They have recently undertaken several projects working on the refurbishment and restoration of pumps for a couple of clients in marine industry. These clients chose to save substantial costs by repairing their pumps with composite material, as opposed to replacing them with the purchase of entirely new equipment.
All work was carried out in the workshop by brush application, using Polyglass Standard; a two pack cold cured polyester/acrylic co-polymer enhanced with glassflake. They are now looking forward to an extended life.
A client operating in the process industry previously had a pump coated by another supplier, which had suffered chemical attack as a result of corrosion. The pump unit was refurbished and coated with Polyglass VE: a cold cured glass flake vinyl ester acrylic co-polymer, which offers superior resistance to chemical attack from equipment used in an immersed environment.
Find out more on how we can repair your pump and provide long term corrosion protection, here.
Did you know we also offer an on-site Thermodynamic Pump Monitoring service which calculates pump efficiency and helps identify significant cost saving opportunities for the pump operator? Head over to our sister company, Corroserve, to find our more.
Corrocoat USA was asked to perform a corrosion assessment for a client on a 2 year old, 4 story sulphuric acid building. The building houses a sulphuric acid generator on a petrochemical plant. Due to incorrect material selection, the process piping leaked acid throughout the building. This caused significant deterioration to the galvanized structure and concrete. The concrete was previously lined with a competitor’s concrete coating designed for short-term exposure in secondary containments. Beneath the leaking areas and around the concrete were pitted with depths of up to 4 inches deep.
Shortly after reviewing Corrocoat USA’s corrosion assessment report, the client hired the team to supply and apply our Plasmet AR3 lining system. The lining system would refurbish the surface and protect against continual immersion. Some work was completed using pre-coated fiberglass sheets. This took place whilst the building was running, and then applied directly at a later stage to the prepared concrete. Throughout this stage of the project, the client addressed the root causes of their corrosion problems.
The surface was prepared using a wet abrasive blast unit, combined with utilisation of a salt remover. This was followed by a high pH cleaning agent to alkalinize the surface. The concreate pH was then tested to ensure compliance to Corrocoat USA’s own standards. Plasmet ECP (Epoxy Concrete Primer) was applied at 6 – 10 mils wet film thickness (WFT). Plasmet ECP penetrates into the concrete protecting subsequent coats from latent moisture, while fortifying the concrete at the surface.
Prior to installation of the new pumps in the building, the 33ftmm x 2ft x 2ft high pump bases were poured using Corrocoat’s Epoxy Polymer Concrete (EPC). The EPC cures to provide a 20,000 psi compression strength and 1,800 psi tensile strength. It can be coated the following day, saving time while increasing reliability.
Pits on the surface were filled with Corrocoat Zip E Screed, a glass flake reinforced epoxy coating enhanced with a proprietary blend of fillers. This allows for resurfacing to direct liquids towards the sump – an important aspect of the customer’s engineering team.
Once the screed was sufficiently hardened, Plasmet AR3 was applied at 48-60 mils dft (1200 -1500 microns). The coating was applied in two to three coats, mixing in an aggregate for non-skid in the high traffic areas. As we have seen in many other applications, the Plasmet AR3 is unaffected in the presence of all concentrations of Sulphuric Acid – it was the ideal solution for this project.
*Note that in one stage of the project, the team in the US had to leave the site for several weeks. This was whilst the Corrocoat Zip E Screed was down in an area without the topcoat. During their absence, there were repeated releases of the 40% sulphuric acid onto the Zip E Screed and the coating held up well. It was easily swept blasted and overcoated after being submerged for days.
On the galvanized steel, the team prepared the surface using a mixture of pressure washing with their 5,000 psi, 4.5 gallon per minute pressure washer. This was in conjunction with the power tools, to prepare the portions of steel that were showing signs of corrosion. They primed with Plasmet ZF and the nuts and bolts were stripe coated using Corrofill E. The structure was then coated using the AR3, applied at 32 – 40 mils dft.
Josh Tankersley, Corrocoat USA General Manager said; “On a project that required constant change of strategy due to variable safety considerations associated with evolving project priorities and coordination, I am very proud of our teams’ ability to utilise Corrocoat materials to transform an otherwise ‘snake bit’ new building, into a sustainable asset that will support the customer’s production efforts for many years to come.”
Corrotech, our Czech partners, recently worked on a project to provide corrosion protection for the internals of a new 450m² carbon steel flue gas desulfurization unit at a coal power plant. This was for a leading provider of innovative technology and solutions, for the energy sector.
Although new, numerous substrate defects were detected on the internal surfaces following abrasive blasting to cleanliness Sa2. These were immediately repaired ahead of a second round of blasting to Sa2 ½.
Due to the size of the unit and the complexity of working around multiple connections, openings, manholes and beams, the internals were split in to 9 application phases. Each phase was treated separately and then connected to the next phase.
Each phase was primed with Polyglass PPA/PPV before the application of Polyglass VEF as a corrosion barrier. All corners were rounded off to a 6mm minimum radius by Corrofill VE. This relieved stress areas before lamination commenced with LR600 and multiaxial cloth 600g/m². Six layers were applied in total with Polyglass VEF WR being applied as an abrasion resistant barrier, and completing the final stage of the coating process.
The team exercised excellent planning and execution. They reached maximum overcoating between each layer and completed the project within the agreed timescale.
Explore more case studies from our international partners here.
Corrocoat Japan were previously contacted by a client, to provide a suitable coating for the internals of a pipe. The pipes would operate in a chlorine gas atmosphere at 200°c. Due to the high cost of metals suitable for this environment, a lining system was preferred and offered by Corrocoat Japan. Following a successful 1 year trial in operation, the client provided 2 more pipes to be lined.
The team selected Corrothane XT; a three-pack cold cured vinyl ester-urethane polymer alloy with glassflake, to protect the pipes. Corrothane XT offers excellent heat and chemical resistance. A resistance of 160°C in a liquid environment. It also provides protection in an atmospheric environment (up to 260°C). The coating system has been widely adopted as a countermeasure in high temperature and high corrosion environments. The team predict the coating performance will still be in good working condition for more than 5 years in this environment.
Find out more about the protection we can provide for new lengths of pipe prior to and during installation as well as refurbishment options for existing pipework, here.
Our Fluiglide energy efficient coating system, first introduced in 1985 has now been applied to literally thousands of pumps worldwide. In every case significant improvements in efficiency are achieved. The performance of the process has been subject of extensive test procedures. This includes evaluation by major manufacturers, utilities and industrial users. Fluiglide materials offer dual benefits. The system not only achieves notable increases in overall efficiency levels, but also provides an effective corrosion barrier. This prevents early fall-off in performance due to nodular growth and surface corrosion.
With record increases in energy costs across the globe, technologies and solutions to help reduce energy consumption and increase efficiency are now more prevalent than ever. Increases in concern relating to the more effective use of energy resources is resulting in the introduction of new technology in coating materials. The aim is to maximise the performance of pumping systems which are in use in areas including power generation cooling water systems, the process industries and water and waste treatment.
The established performance of the Fluiglide friction reducing energy efficient coating system worldwide, places Corrocoat in a dominant position in this demanding and competitive field. We have the opportunity to test and evaluate pumps which have been running, using Fluiglide systems for longer than any other company active in this field. We also offer special abrasion resistant variants of the Fluiglide system, for use where the solids burden is high and abrasive.
For a pump with a lifetime expectancy of 20 years (for example), only 2.5-3% of the cost of pump operation relates to the purchase price of equipment. A further 2-2.5% is attributable to maintenance costs. The remaining 95% is consumed in the cost of the power to run the unit. With the ever increasing cost of energy over the life of a pump running continuously, the potential savings from the average 4-5% improvement offered by the Fluiglide system offers a fast payback on the initial coating costs.
Find out more about Fluiglide, our friction-reducing range of protective coatings, and the huge potential energy savings here.
A UK fabricator of vessels and tanks for multiple industries required additional chemical resistance for two storage tanks due to enter service in the chemicals processing industry. The internal surfaces of the tanks would be subject to constant immersion in sulphuric acid.
Following arrival of the tanks, to our workshop, all internal surfaces were abrasive blasted to achieve the required cleanliness levels and surface profile. This was followed by a blow down, sweep and vacuum to completely remove the dust. The internal angles of the floor/wall were then radiused to ensure full continuity of the coating.
The floor/wall interface of the tanks were laminated using multiaxial glass fabric thoroughly wetted with epoxy laminating resin and rollered into place to remove any trapped air, aid adhesion and provide increased structural strength.
Plasmet AR3, a two pack solvent free polyamine cured epoxy, resistant to strong concentrations of sulphuric and other acids, was spray applied to the required DFT.
AR3 is primarily produced for protection against strong concentrations of sulphuric acid. The product can also be used for other acids and in some strong alkali service duties. Applications include bund areas, tanks, pipe work, floors, decking, structural steel and more.
We were recently awarded a contract to protect 300 new pipe spools of various dimensions by a multinational energy client. Corroglass 600 series was the coating system selected for this project, as it offered the best long-term corrosion protection on the FPSO.
With pipe diameters between 50mm and 300mm. a number of coating strategies were employed including Corroserves’ in-house pipe-blasting and pipe-coating technology, piperolling and a carefully controlled flood and drain technique.
Used primarily on small bore pipes of complicated geometry, the flood and drain technique allows coating to be applied by our trained technicians, into areas which would otherwise not be accessible. This technique has been successfully used for lining pipes with Corrocoat materials for over 40 years.
As part of the Q.A. requirements, the end client requested that a pipe lined by flood and drain should be cut and assessed after coating, to show the excellent coverage, which was advised would be achieved using this application method.
A pipe containing two bends and a tee piece were supplied by the client for the assessment.
The internal surfaces of the pipe were first abrasive blasted and then coated with Polyglass VE Pipegrade, using the flood and drain method. Application was carried out 4 times, allowing the coating to gel between coats and ensure that the coverage was sufficient.
The spool was allowed to cure for 7 days prior to being split along its length, using an angle grinder.
As you would expect, there was a small amount of mechanical damage at the edge of the cuts, but away from these areas the coating was found to be uniform and intact.
Dry Film thickness readings we found to be a minimum of 1,260µm with an average of 1,436µm and a standard deviation of 135.63µm. Readings were taken every 150mm along the length of the pipe. The pipe was spark tested at 17000 KV AC and no defects were found.
Adhesion was then tested in accordance with ASTM D4541. The surface of the coating and the adhesion dollies were abraded with P60 sandpaper. The test dollies were attached using the same batch of Polyglass VE Pipegrade as the adhesive, then tested after 24hrs using a hydraulic adhesion test.
The results of the test were exceptional. The coated test spool had average adhesion value of greater than 20MPa, which was the limit for the test equipment.
Dolly 1 and 3 could not be removed from the surface, whilst the remaining dolly gave a value of exactly 20Mpa.
In conclusion, the coating thickness, integrity and adhesion was found to be excellent along the length of the spool piece, validating the method of application and as would be expected for this high performance Corrocoat lining.
