Abstract
In the past, glass flake filled epoxy resins, with a solids content of 75-90% had been widely used within the oil and gas industry for the protection of the vulnerable splash zone areas (the area which is repeatedly immersed then exposed to the atmosphere) which often suffer from extensive corrosion. With the focus for offshore development now increasingly shared between oil and gas and wind power with its very different construction needs, we look at how ultra-high solids glass flake filled epoxy resins offer benefits for fixed and floating construction projects offshore.
Introduction
Offshore oil and gas facilities are exposed to harsh operational and environmental conditions and are permanently subjected to the corrosive elements of oxygen and water. Due to their location, there are high costs and difficulties associated with maintaining and re-coating these structures. This is particularly so in the jacket areas where coating maintenance can be a very hazardous activity. That’s why the right choice of anti-corrosive coating at the new construction stage can make all the difference.
Coating longevity, increasingly aggressive production schedules, cost reductions and minimising environmental footprint are just a few of the challenges faced by asset owners and their sub-contractors and this has led to an increasing interest in coating systems with a long lifetime, that reduce long-term operating costs and extend maintenance intervals.
In splash zones, two forces combine and corrosion can be severe as this area suffers from the dual impact of atmospheric and immersion conditions; as well as physical damage such as abrasion and impact. It is at the splash zone where a robust, long lasting protective coating is most required. Additionally it is in this area where the effects of poor coating performance can be particularly challenging to rectify.
Ultra-high solids glass flake epoxies for maximum protection
Providing long-term corrosion resistance for splash zone areas can be demanding. As well as the combined corrosive effects of water and oxygen, often mechanical damage and abrasive forces must also be considered - not only when the structure is in service but also during its transit and installation. Recently there has been an increasing move towards the use of ultra-high solids glass flake epoxies for use on different types of offshore structures. This can deliver prolonged service life and reduced maintenance.
Hempadur Multistrength 35840 and 35842 are 99% solids epoxy glass flake coatings specifically designed for splash zone protection. Unlike conventional coatings, these two products are almost solvent-free and contain reactive diluents that contribute to cross-linking (a chemical reaction which assists with hardening the coating), and it is this that significantly enhances the resistance to corrosion.
In addition, the coatings are reinforced with overlapping glass flakes to further enhance their water resistance and strengthen them against physical impact. Their high solids ratio (99 per cent) and low VOC (volatile organic compound) content make them significantly kinder to the environment; it also helps protect those who have to apply the product.
The presence of diluents which are reactive compared to conventional unreactive solvent / thinners also reduce the risk of solvent entrapment which may ultimately impact the performance of the final coating.
Areas of use
Hempadur Multistrength 35840 is suitable for application to splash zone and submerged areas of new construction offshore facilities. It is NORSOK M501 (Edition 6) System 7A/B pre-qualified and can be applied across a wide dry film thickness (DFT) range. For higher DFT applications up to 1000 microns it can be substituted with Hempadur Multistrength 35842. Both products are designed for application without additional solvent being required.
The science behind it
There have been many products that have been developed to protect the splash zone but this coating follows a different technological approach to deliver enhanced protection with a minimal environmental impact. Hempadur Multistrength 35840 and 35842 replace most of the conventional solvent found in similar products with reactive diluents. These low viscosity molecules allow the application characteristics of the product to be maintained. And as these materials fully react with the polymer backbone of the coating, there is a much-reduced possibility of solvent being retained within the finished coating film.
Increasingly as higher DFT’s are being used, often in short construction cycles with little time allowed between coats, it makes sense to use a product with less risk of solvent being retained within the coating film if it is over-coated too early to meet fabrication schedules. This problem is further exacerbated in colder weather when additional solvents may be required in order to continue applying the paint satisfactorily in these conditions.
Physical property development (i.e. hardening) occurs much quicker when compared with lower solids epoxy systems. This allows for quicker handling of coated items. As importantly, the higher volume solids contained within the product means that less paint is needed to coat the same surface area, and this delivers benefits in application time, wastage, paint transport and storage costs.
Key advantages of Hemapdur Multistrength 35840/35842
- Improved performance due to low water permeability
- Can be specified across a wide range of thicknesses
- Impact and hardness develop quickly during curing allowing quicker handling
- Reduced physical damage, better abrasion and impact resistance
- Low environmental impact: high volume solids and low VOC for reduced emissions
- Low solvent content: excellent application, reduced risk of solvent entrapment and improved performance
- Pre-qualified to NORSOK M-501 (edition 6) standard for System 7A and 7B.
- Certified to ISO 20340:2009 for C5M, IM2 and C5M + IM2 categories
Conclusion
Challenging offshore conditions are encouraging oil & gas offshore facility operators to search for more effective solutions from their coating providers. Hempadur Multistrength 35840/35842 are unique low solvent and high solids coatings offering offshore facilities tough and consistent corrosion resistance.
As always Hempel is committed to assisting its global customer base to prolong their assets through the provision of industry leading and trusted coating solutions.
