Watching Paint Solidify

Paint both protect and provide a new aesthetic impression. Paint is applied to many different surfaces (technically called substrates) like structures such as ships, bridges, buildings, vehicles, and oil & gas. The paint on the steel substrate and paint film is the main focus of the present investigation.

Imagine a liquid paint applied on a steel substrate like ship or oil and gas structure. The chemical curing and physical drying of a liquid paint are relatively fast on the surface-air interface as compared to the underneath layers. A skin layer develops as the processes of curing and drying proceed and a number of changes happen in the freshly applied paint. The main changes are; development of cohesive and adhesive forces, decrease in the paint film thickness, increase in modulus (stiffness), glass transition temperature (Tg) and ultimately when a network is formed the volume changes and give rise to an internal stress. The magnitude of the internal stress in the paint film gradually increases and with time reaches its maximum value depending on the degree of cure and the amount of retained solvents. The temperature of the environment along with humidity plays a critical role in defining the Tg and modulus of the paint film that is directly associated with the internal stress. Therefore, it is important to investigate Tg, modulus and internal stress at the same time and at different temperatures.

Figure 1) A part of DMA setup

Figure 1) A part of DMA setup

Figure 2) A part of the tensile stress setup

Figure 2) A part of the tensile stress setup

A team headed by Senior Chemist Saif Ullah at Hempel is investigating glass transition temperature (Tg), modulus (stiffness), the coefficient of thermal expansion (CTE) and tensile stress at Aalborg University’s lab facility (Figure 1 and 2) with the help of Professor Jesper de Claville Christiansen and his team. This research work is part of the Fast Track Consortium and funded by Innovation Fund Denmark.   

The overall aim of the project is to get a better understanding of what happens in the curing process of the paint film applied on the steel substrate and to develop fast screening methods that will enable us to save development time and produce tough and resilient paint.

Electroplating of Fe-C coatings as an alternative to hard chrome coatings

- PhD project, collaboration between 1) Technical University of Denmark (DTU), 2) OCAS NV, ArcelorMittal Global R&D Gent (Belgium), 3) a. h. nichro Haardchrom (Denmark) and 4) Fast Track - Materials Solutions (Denmark).

Plating picture2.jpg

Strong concerns about the harmful effects of selected chemicals on humans and eco‐systems have resulted in chromium trioxide being on the list of substances included in Annex XIV of REACH ("Authorisation List"). The ban has huge consequences for the traditional hard chrome plating as the predominant current process to produce hard and wear resistant coatings for the aerospace, automotive, drilling and military industries.

Already in 2014, the need of environmental friendly alternatives to hard chrome encouraged the Danish hard chrome plater a. h. nichro Haardchrom, in collaboration with the Technical University of Denmark (DTU) and with financial support by the Danish Ministry of Environment and Food, to investigate the potential of novel types of coatings. Without compromising for neither the excellent coating properties nor the ease of a straightforward deposition technology, electroplating of iron-carbon coatings revealed promising results and a PhD project on surface engineering of Fe-C coatings was started in 2017. The project is a collaboration between the Technical University of Denmark and the companies a. h. nichro Haardchrom (Denmark) and OCAS NV, ArcelorMittal Global R&D Gent (Belgium) and it is further supported by the societal partnership; Fast Track - Materials Solutions (Denmark).

 
Electroplating setup - by Jacob Obitsø Nielsen

Electroplating setup - by Jacob Obitsø Nielsen

 

 

Although electroplating of iron has been developed a century ago, it has mainly been used for localized reparation of worn surfaces and its full exploration and application as a cheap, non-toxic, versatile plating process with a huge potential for engineering the microstructure and associated properties of the Fe-C coatings is now addressed in the project. With systematic lab-scale experiments, the plating process is optimized and challenges of upscaling for final implementation into industrial processing are tackled. These imply, for example, the risk of oxidation of Fe2+ to Fe3+ in the electrolyte, which even in case of low concentrations of Fe3+ will reduce the current efficiency and cause the coating to become brittle, stressed and pitted. After two years of development, a proof-of-concept has been established for an innovative process being able to handle the oxidation without chemical adjustment and being able to produce hard Fe-C coatings with similar wear resistance as hard chrome. Thorough microstructure characterization using state-of-the-art and complementary characterization techniques reveals the internal structure of the Fe-C coatings and enables understanding of its growth as a prerequisite for further tailoring of the plating process and, hence, the coating properties. As a next step towards successful implementation into industrial processing for large-scale synthesis of the hard and wear resistant surfaces, the Fe-C coatings will be tested on pilot-scale under surface lubrication, being typical for bearings or gears. While lubrication straightforwardly handles the main concern for the Fe-C coatings, its low corrosion resistance compared to hard chrome, further development and dedicated plating solutions are considered to solve the corrosion issue and, thus, widen the applicability of the Fe-C coatings while maintaining the mindset of a feasible and environmentally friendly process. The combined strengths of the stakeholders allows to act on specific needs from the industrial partners and brainstorm about possible solutions with experts from both academia and industry.