A large and complex network of pipelines is as important to a country as arteries are to a human body. Pipelines that transport and distribute water, steam, oil, gas, chemicals, etc., are of utmost importance for the national and global economy. The arteriosclerosis of the pipeline system is the electrochemical deterioration, or corrosion. And that particular disease attacks pipelines and accessories made of both metals and non-metals.
Oil & Gas industries amongst most vulnerable
Corrosion predominantly affects pipeline made of metals such as copper, aluminum, cast iron, carbon steel, stainless steel and alloy steel pipes used for buried, underground, submerged or other pipelines. Offshore Oil and Gas Platforms are amongst the industrial areas which suffer the worst from corrosion due to the atmospheric conditions they are exposed to, like salt water, extreme cold or heat, high concentrations of chlorides and the degrading effect of UV – light from the sun.
Oil & Petrochemical Refineries are another such case with hundreds of miles of piping, valves and flanges. Crude oil, in itself, is not corrosive. However, there are some impurities and components often found in crude oil that could cause corrosion in pipelines, vessels and refinery equipment, such as atmospheric columns, overhead lines, exchangers and condensers. Among these are chlorides, carbon dioxide, organic chlorides, organic acids, sulfur and bacteria. Resulting corrosion can weaken the structure of a pipeline and make it unsafe for transporting potentially hazardous materials.
A variety of means to control corrosion has been around for many years but the issue remains a thorn in any engineer’s or technician’s side as there is no final way to win this perpetual battle.
The ongoing search for better solutions
Therefore, the battle against corrosion is being fought on many fronts. Just how many, the winners of the Materials Performance Corrosion Innovation of the Year Award nicely illustrate. Among this year’s winners were Seikowave Inc. with a 3D structured light, a scanning process dedicated to integrity assessment; American Innovations, with the five analog channels and two digital channels RM4150, created to monitor rectifiers used in cathodic protection systems, which measures alternative current and direct current volts and amps, pipe-to-soil potential, shunts, instant off, line power presence, and more with 1% of reading accuracy; MesoCoat’s CermaClad™ technology, that utilizes a high-intensity arc lamp to rapidly fuse protective, proprietary cladding materials on steel pipes and tubes, plates, sheets, and bars; and the DeFelsko Corporation’s new PosiTector gage body that accepts all coating thickness, environmental, surface profile, and ultrasonic thickness probes.
EuroCorr 2014, European Corrrosion Congress, introduced a number of new corrosion-prevention technologies as well. Some of these innovations are already being used, while others are expected to be marketed soon.
The Belzona 3411 is an encapsulating membrane that is a hybrid polymer coating that can adhere to any shape on a flanged joint. This development keeps moisture out of the joint and prevents corrosion better than any other method currently available.
BSI has developed new spray linings that are designed to withstand immersion at high temperatures. This prevents corrosion on things such as underground tanks.
Bio-Logic demonstrated a variety of corrosion detection products, including battery testers, electro-chemical testing kits, scanning software and materials testing kits.
Self-healing anti-corrosion coatings
Paint and epoxy coatings of varying types and degrees are the weapon of choice for coating pipes, flatworks and support structures and it is a full time job keeping the corrosion at bay. Lately they’ve been joined by a number of inventive thermoplastic resin coating systems, like Belzona’s that are taking the market by storm. These encapsulation methods are a big step ahead as they form exactly to the substrate, have a built-in corrosion inhibiting agent, do not adhere, easily peel away when needed and can even be re-used.
But the ultimate solution scientist are working on, are the self-healing coatings. Defined by the Corrosionpedia as “coatings that possess the internal capability to repair sustained damage by themselves, or with some outside stimulation”, self-healing coatings are already used in automotive refinish coatings, smartphone production etc. Many are produced by the addition of substances to existing materials, and have the ability to sense cracks and then initiate repair via microcapsules of resins, which rupture and react.
Self-healing epoxies can be incorporated into metals in order to prevent corrosion. These coatings intelligently respond to mechanical or chemical damage caused by the external environment and to reproduce their original properties, including their adhesion to the substrate and integrity. They can be produced using macromolecular compounds, ceramics, metals and composites.
A new prototype of the technology has been developed by Asst Prof Yang Jinglei from Singapore’s Nanyang Technological University. The synthesised microcapsules are tuned to resist water or solvent, making them suitable for coatings and paints of underwater structures. This technology could be applied to waterborne or solventborne paint systems, especially for underwater and underground structures that require heavy duty corrosion protection.
Scientists from the Max-Planck-Institut in Düsseldorf and in Mainz have also succeeded in embedding a few 100-nanometre-sized polymer capsules containing anticorrosion payloads in a coating. They applied the coating to a metal and exposed the metal to corrosion through a crack in the coating. Thereupon, the capsules opened and released the protective payloads. As soon as the corrosive attack ended, the containers closed again.
“We now want to enclose the healing substances and the anticorrosion substances together in the same capsules,” says Crespy, as only both substances combined can provide comprehensive protection against the destruction caused by rust. Whereas the anticorrosion substances quickly stem the corrosion, like the initial halting of the blood flow in the case of injury, the healing substances restore the enduring anticorrosive effect of the coating. However, up to now, it has not been possible to encapsulate both substances under the same chemical conditions,” said Daniel Crespy.
Chromates still set the standard in terms of anticorrosion coatings and their use is still widespread, however, they are being banned in an increasing number of applications due to their toxicity. One of the challenges for the scientists in the field of self-healing anticorrosion system, is therefore to identify inhibiting substances which are as effective, as chromates. And the second, to find a way for healing substances to reach a defect faster and in greater quantities to be highly effective. If they succeed in overcoming these issues, it is entirely possible that metal coatings will be the equal of living skin when it comes to powers of self-healing.