AIRCRAFT TECHNOLOGY S ANNUAL PUBLICATION FOR THE MRO PROFESSIONAL

2014 AIRCRAFT TECHNOLOGY S ANNUAL PUBLICATION FOR THE MRO PROFESSIONAL Supported by:

Aircraft primers Aircraft are pushed to the limits on a daily basis, tested against the harshest of environmental factors, so paints and coatings must provide sufficient protection. Primers play an important role in this, and here, four primer manufacturers and one MRO discuss product development, application techniques and future outlook. promotes adhesion, says Julie Voison, product manager at Sherwin- Aprimer Williams Aerospace, when explaining how a primer creates a bond between the substrate and the topcoat. A topcoat is designed to act as a line of defence against environmental elements but it isn t necessarily designed to adhere and hold on directly to a composite or aluminium, so the primer is the bond that links it all together. Indeed the topcoat is what makes an aircraft aesthetically attractive and an operator s unique livery is what sets its fleet apart from competitors. However, pre-treatments a thin layer such as soap that goes onto the substrate before the primer and primers also play a vital role in an airframe s coating, by protecting it from corrosion, wear and tear, debris, heat and UV exposure. Product development In recent years coatings and paints manufacturers have developed their products to support the growing demand for increased corrosion protection. Each operator wants its aircraft to be as robust as possible and the number one thing is that everybody wants to protect their assets, says Voison. Having a primer that offers low VOCs (volatile organic compounds), simple application processes, corrosion protection and durability is vital. The primary goal for manufacturers is to meet customer demand as well as "eliminate the hexavalent chrome", says Phong Lai, director of sales and marketing. Offering a solution that gets rid of this harmful substance, which is apparent in original primer systems, has quickly become a goal of all OEMs, as long as performance is not sacrificed. According to Air France Industries KLM Engineering & Maintenance (AFI KLM E&M), chromefree and low VOC paint schemes are less harmful to both the environment and humans. Therefore coatings manufacturers such as AkzoNobel, Mankiewicz, PPG Aerospace and Sherwin-Williams now offer a variety of primers that help improve the sector s footprint, as well as combat the extreme factors of the environment. The main goal is to prevent corrosion," says Réne van der Hof, process engineer coatings specialist, AFI KLM E&M. Legacy products that utilise solvent-borne technologies, where strontium chromate is the corrosion inhibition technology used have previously been the industry standard in ensuring aircraft durability, says Mark Cancilla, global platform director aerospace coatings, PPG Aerospace. New technologies include corrosion inhibitors that do not utilise chrome, and reduce the VOC levels of the primer products, as well as include improved efficiencies in application, he adds, and it's these solutions that are proving popular with operators. Similarly, AkzoNobel focuses on the introduction of next generation, environmentally progressive products such as chrome-free and high solids exterior primers, says Michela Fusco, marketing segment manager at the company. One of the company s latest additions to its exterior primers portfolio is its Aerodur LV 2114 primer, an environmentally sound and corrosion resistant direct to metal primer (DTM), which eliminates the need to use any kind of metal pre-treatment. The product provides necessary adhesion and corrosion resistance to meet the stringent specification requirements of AMS 3095A, notes Fusco. "The primer must have good adhesion with the surface and corrosion inhibiting properties," agrees AFI KLM E&M s Van der Hof. AkzoNobel also prides itself on its "complete offering of primers for the needs of aircraft maintenance, including structural and repair primers, says Fusco. Its chrome-free primer, Aerodur 2100 MgRP, which utilises magnesium technology to give equal or superior corrosion resistance compared to existing chromate containing primers, has recently qualified according to AMS 3095A, she adds. It's these products that pave the way towards a greener sector and most importantly, for operators, tackle corrosion. According to Fusco, the design features and requirements of AkzoNobel s primers are very complicated but its experience allows it to offer customers products that combat stresses like rain erosion, huge temperature differences, chemical resistance and abrasion. PPG has also been developing new DTM materials that will give clear benefits to the industry 48 MRO YEARBOOK 2014

through reduced weight and ease of application, says Cancilla. PPG focuses its product development on continuous improvement of field performance, durability and corrosion resistance, with more environmentally friendly materials, improved application robustness, and lighter-weight materials, says Cancilla. More recently PPG has introduced chrome-free solutions such as its pre-treatment Desogal and eproxy primer Desoprime. Desoprime, which has now been in the industry for two years and is used on all 737NGs in production, has passed both OEM and AMS specifications, says Cancilla. And since PPG acquired specialty coatings company Deft in April this year, it can now utilise the Deft product line, which "uses waterborne technologies within many of the products, helping to reduce VOC levels, notes Cancilla. Sherwin-Williams also focuses on product development in order to offer more corrosion-resistant, protective products designed for a variety of substrates: steel, aluminium, fiberglass, composite materials and magnesium. As the industry is going through adaptation we have to work to keep our technology up to date and fresh and be prepared to offer customers options when they are ready, explains Voison. Sherwin-Williams range also provides the painter with a choice of environmentally supportive primers such as its chrome-free epoxy primer, epoxy primer surface and urethane primer. Mankiewicz offers customers two systems; a chrome-free epoxy primer, which can be directly applied over conversion coatings, and for structural coatings it offers a water-based epoxy primer. Lai explains how Mankiewicz has developed a system called a non-chromate base coat/clear coat that allows the chrome-free primer to be directly applied over a non-chromate conversion system, offering airlines a completely green system. The primer systems that have been, and are being, developed by OEMs allow operators to enjoy a greener footprint, weight reduction, and ultimately reduced costs. However, reducing the weight of a primer when the thickness has to be "20-25 microns", according to Lai, presents some challenges, meaning OEMs have to adopt tough strategies and continue to innovate in order to meet customers' demands and expectations. Cancilla describes PPG as taking an aggressive path in its development activity with regards to reducing the weight of its primers, highlighting its 'Aerocron' electrocoat system as one of its key products in this movement. Aerocron is designed to maximise corrosion with the use of non-chromate corrosion inhibitors, and the application process by design, will minimise the film thickness needed to protect the part, he adds, allowing for a reduction in weight. A common demand from operators is for primers to maintain minimum thickness to allow for weight reduction while providing an acceptable topcoat appearance. Weight means fuel consumption, and fuel consumption means higher operating costs, and with all the new product developments that are in the pipeline "weight reduction is on the radar screen all the time, says Fusco. With the introduction of DTM primers it looks as though the industry is getting closer to a lightweight solution, but with the focus still being on chrome-free primer technology, perhaps there is still more to learn in relation to applying chromefree primers directly to metal, and some challenges to face. Fusco notes that this is an area for future product development, highlighting the interest that AkzoNobel has seen with its DTM chrome primers in the past. However, PPG and Deft have already started "developing new materials that will be designed to apply directly to metal surfaces without the use of chromated corrosion inhibitors", says Cancilla. Working with composites The aviation industry has had to adapt to working with advanced composites and this has presented the coatings business with various challenges; most notably OEMs and MROs have had to develop new application techniques and approaches when working with composites, as opposed to aluminium substrates. Different rules apply with composites and non-composites, agrees Voisin, explaining that a primer s role changes depending on the surface that it is applied to. On an aluminium substrate the primer protects against corrosion and when used MRO YEARBOOK 2014 49

on composite materials, instead of protecting corrosion, a primer would fill in the weave of the composite and smooth that out in preparation to receive the top coat finish. You are still putting down a similar process but they are doing two different things, she explains. Adhesion is different when working with an alloy, comments Lai, agreeing that a primer has to be altered when working with composites, in order for it to stick. Other requirements also change when working with composites due to the no corrosion factor. Mankiewicz, for example, conducts additional tests to assess factors such as salt spray and UV exposure. While composites offer environmental and financial benefits there are some challenges when it comes to working with such advanced materials. Due to the different chromate capability of the composite surfaces, defects can sometimes occur and micro pinholes can be found, says Lai, meaning that the primer has to have the functionality to highlight the defect areas, allowing it to be fixed before protective layers are applied. In addition, the mould used when working with composites utilises a lot of release agents to prevent any composite getting stuck in it, explains Lai, but this release agent is prone to surface contamination. And if the operator doesn t complete the process correctly from start to finish it can become very labour intensive. While there may be changes to consider when developing the primers, AFI KLM E&M s Van der Hof states that "there is no difference regarding the application of a primer in relation to the surface". According to AkzoNobel, "chrome-free primers are more commonly accepted [and] it is expected that they will be applied on composites as well". PPG says it has already developed a chrome-free As the industry is going through adaptation we have to work to keep our technology up to date and fresh and be prepared to offer customers options when they are ready. Julie Voison, product manager, Sherwin-Williams Aerospace primer system, Desoprime CF/CA7501, that is already on use on the 787 and will likely be used on future composite aircraft. Application processes An operator must ensure that it has the correct solutions and processes in place to keep AOG (Aircraft on Ground) situations and downtimes to a minimum. Therefore, having the best, most effective primer systems in use and application techniques and processes in place is paramount. Aircraft coatings are applied by spraying and, in recent years, such techniques have advanced and according to AFI KLM E&M "high pressure electrostatic spraying has been adopted. In order to work with the new chrome-free technology there have been "some changes" of materials and processes with regards to pre-treatment products, says Van der Hof, and "most paint-sprayers have had to adapt to new products when they spray it for the first couple of times". PPG approaches customer downtimes in three different ways, according to Cancilla. The company reviews product performance and new technologies to help support continuous improvement in product service life. Secondly, it focuses on the robustness of its application processes through its development process, called Secure Launch, which allows technical personnel to develop the application process while PPG develops new products. Additional investment is also placed in a substantial, global technical service organisation that is comprised of "skilled and experienced" workers who support its customers in the application of PPG products at their facilities, says Cancilla. With regards to primers, the effect on downtimes is pretty much non-measurable says Mankiewicz s Lai, as all primers have the same thickness requirements ranging from 20-25 microns and all dry pretty much the same, emphasising that there is miniscule difference between products. However, Lai does note that some products require 30 minutes induction time, so once they are mixed together they have to reset for that duration to allow for the reaction to start. Other products do not, so the big difference in time is application after the protective layer. To the maintenance market the process of applying a primer is different to that of the OEM's process, and some companies don t have the controlled environments that others might. This can create "quite a challenge for the primer", according to Lai, as it has to be as "easy to apply in an environment ranging from 60 degrees Fahrenheit all the way up to 95 degrees Fahrenheit". The coatings business can help improve downtimes and application processes by making it easier to apply coatings, with less drying time, according to Van der Hof. He says that this is very 50 MRO YEARBOOK 2014

www.swaerospace.com EXCEPTIONAL APPEARANCE FROM TOPCOAT... TO BOTTOM LINE difficult as it s always a balance between several coating properties such as levelling and drying time. Future outlook It is abundantly clear that this particular sector of the industry is extremely proactive with its product development, with each primer manufacturer innovating in order to deliver increased value to the industry, says Cancilla. AkzoNobel, for instance, is currently working on introducing a new chrome free primer, Aerodur 2111 to the maintenance market. The product, which is in the final stages of the OEM approval process", has been successfully applied on a few commercial aircraft, according to Fusco. And so far, the introduction of the product to the paint shop has been very positive, and painters are enthusiastic about its ease of application. Fusco adds that after drying the product looks and feels very smooth, even on places where the application is normally very difficult. However, Fusco sees the acceptance and trust of chrome-free primers as a step to overcome, commenting that not all people feel comfortable about chrome-free. Moving away from chrome containing primers is not an easy step in a conservative industry, she adds. AkzoNobel does believe that a phased approach should be adopted to help build trust in chrome-free technology as working with the supply chain would be the way forward for a successful transition. Voisin agrees that the sector is still going through an adaptation of chrome free primer technology. She sees Sherwin-Williams as being at the forefront of the development with five different products that vary in performance and type of technology, catering to its customers varied needs, whether it s fast dry time, skydrol resistance or urethane or epoxy technology that they require. Sherwin-Williams plans to focus on three main areas within the sector to encourage reduction: weight, cost of application (from processing time to the cost of a can of paint) and environmental impact. Similarly, PPG says it is committed to advancing the performance of its products, with the company continuing to focus on improvements in application efficiency, corrosion protection levels, and minimum film thickness, according to Cancilla. In addition to challenges presented by chrome-free primers, Voisin sees the evolution of composite substrates" as playing a bigger role in future developments. She explains that where composites previously made up a small fraction of the total aircraft substrate, there are now aircraft that are heavily composite, such as the 50 per cent composite 787. As a result, the roles of primers will change and increase in usage. Going forward, Mankiewicz wants its products to perform to help the environment and also perform to the regulations required in Europe. Due to different regulations all over the world the OEM hopes to develop a universal product, which abides by global regulations and minimises any challenges that various regulations present. It s clear that a primer manufacturer's main aim is to produce solutions that offer corrosion protection, as well as reducing the impact on the environment as far as possible. The recent developments that have been seen within the coatings business are definitely encouraging and the steady pace of innovation seems likely to continue. Sherwin-Williams Aerospace proudly introduces the SKYscapes basecoat-clearcoat paint system that saves time and money imagine being able to cut as much as 30% from your painting process time and eliminating most bake cycles. Meeting SAE AMS 3095 certifications, it provides the superior appearance and durability that the aviation industry expects from Sherwin-Williams. MRO YEARBOOK 2014 51