Dan Diehl, Paul O’Malley & Lou Ronsivalli.
Raising the bar09 January 2013 / by Staff Reporter (author) / Dubai
Corrosion is an endemic problem in GCC structures, causing increased maintenance work and reduced lifecycles if the necessary measures are not undertaken in the construction phase. FM Magazine talks to Richard Cowl, Global Sales Manager for Jotun Powder Coatings, about epoxy coatings as an anti-corrosion solution.
“You’ll never stop corrosion,” declares Richard Cowl, Global Sales Manager for Jotun Powder Coatings. “You might do for a finite period of time but there will be a weakness in the system no matter what. At the end of the day, mother nature will win.”
The key question is, therefore, how long you can make that ‘day’ last. Preventing corrosion occurring for as long as possible is the key objective of those providing anti-corrosion solutions. The benefits of investing in the right anti-corrosion solution or, more appropriately, the right combination of solutions in structures include increased public safety, maximised asset life, environmental protection and more cost-effective operations in the long run.
A landmark study in 2002 initiated by NACE International, the largest organisation in the world committed to the study of corrosion, showed that the total annual estimated direct cost of corrosion in the United States is a massive $276 billion – approximately 3.1 per cent of the nation’s gross domestic product (GDP) and not much less than the GCC’s combined GDP. Entitled Corrosion Costs and Preventive Strategies in the United States, the study estimated that 25 to 30 per cent of annual corrosion costs in the US could be saved if optimum corrosion management practices were employed.
In the harsh climate of the GCC, corrosion becomes an even more important issue to factor into the construction process. “We have a really aggressive environment here in the Gulf area,” explains Cowl. “It’s got the second most saline bed of water in the world. It’s very hot, which accelerates any chemical reaction. There’s a lot of salt around the place; this salt is airborne as well. And it’s very humid. Another problem you have in the Gulf is what they call the 'subkha', the water table, which is very high and extremely aggressive also. So you have the ideal environment for corrosion.”
The result is that annual rates of corrosion reactions in the Gulf are 10-20 times faster than in parts of the US and Europe, where actively corroding steel corrodes at a rate of 1mm a year. Corrosion is a naturally occurring phenomenon commonly defined as the deterioration of a substance (usually a metal) or its properties because of a reaction with its environment. Corrosion can cause dangerous and expensive damage to everything from automobiles, home appliances, and drinking water systems to pipelines, bridges, and public buildings.
In bridges or buildings, corrosion begins when the alkalinity of concrete is compromised by the intrusion of chlorides, water and oxygen. This leads to rust. As the reinforced steel bar (rebar) rusts, it increases in volume. That increase in volume exerts pressure on the concrete until it eventually forces the concrete off – called ‘spalling’ in industry terms – leaving a naked grid of rebar.
Carbonation is another cause of corrosion. This is when carbon dioxide in the air reacts with the moisture in the concrete to reduce its pH level, causing accelerated corrosion rates for unprotected steel. As rebar is concealed by concrete, the problem with corrosion is that often it isn’t noticed until rust stains or cracks can be seen on a wall – at which point it is too late to remedy.
“If you go around Dubai or Abu Dhabi, you’ll see structures where the reinforcement bar has been so badly corroded it starts to destroy the concrete,” says Cowl. “So the whole strength of that structure is diminished. Repair and maintenance costs are very high. So when we come in, we basically recommend that substructures should be heavily protected, and maybe up to the first floor. After that, you don’t need it; black bars on their own are probably fine. It’s not so aggressive.”
Jotun Powder Coatings is a leader in the development of anti-corrosion protective coating solutions. Headquartered in Dubai and with regional manufacturing plants in both Dubai and Saudi Arabia, Jotun Powder Coatings serves three market segments: architectural, industrial and specialities, and functional. The latter includes the production of thermosetting fusion bond epoxy (FBE) powder coatings for pipelines, valves and rebar. Jotun Powder Coatings sells its FBE coatings to applicators, who buy the steel, prepare surfaces and apply the product. Once the steel bars are coated, they go to a construction site or trading company.
The FBE coating process begins when the steel rebar is cleaned by grit shot blasting. Then, the rebar is heated to around 240 degrees Celsius before the coating powder is sprayed onto it. The residual heat of the rebar cures the coating to form a continuous film which is then quenched with water. The most critical part of this procedure occurs during the curing process when a chemical cross-linking reaction is triggered. It is this chemical reaction which gives the powder coating its most desirable properties.
FBE coatings are governed by the American Society for Testing and Materials (ASTM) standards –standard A775M specifically. Fusion-bonded epoxy-coated reinforcing bars (FBECR) have been around for more than 30 years in the US, and have developed a good track record there. For example, independent studies into bridge structures suggest that a single layer of epoxy coating adds an average of 40 years or more to the structures’ lives. If two layers are used, it adds 80 years onto the standard black bar.
In the GCC, epoxy coatings are widely used in a range of applications but only around five per cent of all black bar in UAE buildings is coated.
“It could never be 100 per cent because we’re talking about corrosion protection of rebar from the substructure up to the first floor,” explains Cowl. “But we would want to see increased use of it. There is a lot of experience of epoxy coating as an anti-corrosion coating: steel pipelines have it and cars have it. So what’s the difference? One you see, one you don’t.”
Cowl says the problem is there are many myths prevailing in the market surrounding the performance of FBECR. He concedes that there have been isolated incidents where the product was found wanting. But, he insists, these have been few and far between and have often not been fully understood.
Most engineers know about epoxy coatings but I would say most people’s points of view are probably biased a little towards what they've heard rather than what they know.
“Most engineers know about epoxy coatings, but I would say most people’s points of view are probably biased a little towards what they’ve heard rather than what they know,” Cowl laments. “So part of what we’re trying to do is to educate people about the realities of the product.”
Using FBECR is not the only anticorrosion solution. Indeed, there are a host of other techniques, which can be grouped into five main methodologies: coating the reinforcement bar, such as using FBE coatings; barrier films – neoprene membranes, surface coatings and penetration sealants; electrochemical techniques – cathodic protection and sacrificial coatings; concrete composition – water cement ratios, pozzolanic materials and corrosion inhibitors; and the design itself, such as increasing concrete cover.
What we’re trying to say to consultants, architects and engineers is that you have to adopt a multifaceted approach. One system alone is not going to work perfectly.
“Theoretically, as far as I’m concerned, the most important part is the design,” says Cowl. “Then you have protective barriers and such like. But all with their own problems. What we’re trying to say to consultants, architects and engineers is that you have to adopt a multifaceted approach. One system alone is not going to work perfectly.”
Cowl cites the example of using epoxy-coated rebar. Its effectiveness can only be optimised if there are no corrosion materials already present on the rebar itself, or in the cement or in the concrete mix – aspects beyond his control. In this region, all the methods mentioned are being utilised to varying degrees. Cowl says that often it is down to the personal preference of the consultant, engineer or contractor.
“You get some of them that willl say ‘Of course we use it, why wouldn’t we?’ Others will say ‘Not over my dead body!’ because they’ve had a bad experience. We’re all prejudiced in favour of what we know. So it totally depends on the people involved as to which corrosion control system they use here. I would say Dubai is lagging a little bit
behind the rest of the GCC. In Dubai, it really depends on the contractor. If you have a contractor or a consultant who knows the product, whichever product, then he will use it. If he doesn’t know it or he’s heard that it’s not good, he won’t touch it. And there are a huge variety of potential solutions out there in the market at the moment.”
Cowl cites The Palm as a typical example of how things are done in the rapidly expanding emirate. Parts of The Palm have epoxy coating on the reinforcement bars and parts of it don’t, because of different consultants and contractors working there. As a priority, Cowl says epoxy-coated rebar should be used up to the first floor of all buildings of up to one kilometre from the coast. Off-shore projects such as The Palm should be prime candidates.
Cowl says that given the fast-track nature of Dubai’s construction industry there is often undue pressure on the professionals involved to simply complete projects on time and then move on. He sees little sign of this changing, with a slew of megaprojects on the cards. Abu Dhabi, however, is more progressive in this respect, its municipality recommending the use of epoxy coatings and whatever other corrosion control methods for rebar. Across the rest of the GCC, there is an increased awareness at the governmental level of the benefits of using FBECR and, consequently, of the need for legislation to this effect.
“If you look at Qatar, for example, there is a governmental decree that all their buildings have to have epoxy coating,” says Cowl. “Where the Asian Games infrastructure is being built, all of those stadiums and structures have epoxy coating. Oman has a governmental decree out that you have to use epoxy coated rebar – especially near to the coastal areas. Kuwait is starting to push this along. In Saudi Arabia, one of the largest companies there is Saudi Aramco. If you are doing a project for Saudi Aramco, you have to use epoxy-coated rebar. These guys have done all the tests, they’ve seen how good it is and they know the value they’re getting from it.”
Our objective is to make sure that the owner is getting the best value for money. Pound-for-pound, to use a boxing term, I truly believe that epoxy coating is one of those solutions.
Cowl says the cost of using epoxy-coated rebar is minimal. In a fairly heavily rebarred structure, he estimates that it would increase the total project cost by half to one per cent. The only caveat is that the FBECR must be handled more delicately than normal black bar to avoid damage to the coating. “Our objective is to make sure that the owner is getting the best value for money,” he says. “Pound-for-pound, to use a boxing term, I truly believe that epoxy coating is one of those solutions.”
Cowl says that for the facilities manager, the value of using FBECR cannot be underestimated. Given the fact that corrosion in rebar is often detected too late, the cost of repair is phenomenal. “So for the person maintaining that building, and for the owner of the asset, the simple use of epoxy coating will make him sleep much easier at night.”