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Self-repairable Zinc-free Weldable Anti-corrosion Primer for the Steel protection

Final Report Summary - WELDAPRIME (Self-repairable Zinc-free Weldable Anti-corrosion Primer for the Steel protection)

Executive Summary:
The global production of steel is in the range of 1400M tons, worth nearly €1trillion. The steel demand in Europe in 2011 was estimated to be 145M tons, of which 39M tons p.a. for the construction sector and 16M tons p.a. for structural steel. Most of this steel is carbon or mild steel (as opposed to stainless steel) which corrodes at a high rate and although there are a significant number of anticorrosion solutions on the market, protective coating is most widely used, thanks to its low cost and high versatility. Often, an anticorrosion primer is applied just after manufacturing of steel in order to prevent rusting during storage and transportation before fabrication (cut, weld, drill, etc.).
Most anticorrosion primers last max 6 months due to poor quality or mechanical damage resulting in corrosion. Additionally, these anticorrosion primers are often too thick (-50µm) preventing weld quality, so time consuming localised grinding is done to remove the primer. If the primer is thin enough (-25µm) to allow welding, its anticorrosion properties are so limited, not reducing the risk of corrosion. Above all, the increased zinc content in the weldable primer formulation in order to achieve the anti-corrosion property result in health hazards and discomfort during fabrication process as it releases significant amount of zinc fumes. Alternatively, primers are simply not used at all but the expensive and hazardous blast cleaning of steel is carried out before fabrication which may sometimes be too late that it results in huge material waste and cost. The problem to be solved is the inability of the weldable primer produced today to allow both good quality welding and durable corrosion protection without health hazards.

The WeldaPrime project aim was to develop a primer which is zinc-free, has low organic content, and can be applied as a thin coating to provide weld-through capability without affecting weld quality and yet providing adequate corrosion protection.

Steel, especially carbon steel, is used widely in number of industry sectors, such as oil and gas, chemical, construction and marine industries. The protection of carbon steel against corrosion is critical not only in-use but also during transportation and storage at the steel yard. Zinc-based primers are the most commonly used method for corrosion protection of the steel, protecting the steel via sacrificial galvanic protection mechanisms. However, maintaining a balance between corrosion protection and weldability can be a challenge.

Typically, coatings thicker than 25-50 microns are necessary to achieve good protection against corrosion but this can lead to difficulties in the welding process due to the inability to strike a weld through the thick primer. Additionally, the incorporation of organic materials from the coating in the weld or entrapment of zinc fumes and gas can make the weld porous and have a significant negative impact on weld quality.

Thus, removal of the primer is often undertaken by grinding or blast-cleaning before welding, leading to an additional step and hence additional costs. In addition, by-products like zinc fumes from
zinc-rich primers have a significant health hazard associated with them and can potentially lead to zinc fever for the welders. Overall, the use of traditional zinc-rich primers can lead to increased post-weld cleaning costs, reduced quality, greater rework, and an overall reduction in productivity.

The WeldaPrime consortium wanted to provide the European steel fabrication industry with an enabling technology that allows the steel to be protected with a new, high performance primer coating, with high levels of corrosion protection simultaneously with good weldability and without the use of zinc. Through the 3 years' project, the focus of WELDPRIME project partners achieved an understanding of the key chemical and nano-structural components necessary to allow such a primer coating film to be developed. The use of sol-gel chemistry and suitably functionalised nano-additives allowed the development of a unique low-organic but flexible, durable and weldable primer, with the following attributes:

- Zinc-free formulation
- Good corrosion protection using enhanced barrier of sol-gel based coating and excellent adhesion to steel substrate.
- Deposition by standard application procedures used in industry (e.g.: spraying)
- Good weldability: Weld-through (without removal of primer), minimal or no impact on cutting speed, good weld quality (very few pores due to low organic content)
- Excellent next coat compatibility to most commonly used epoxy type primers/build coats, for both as-applied and aged primer
- No toxic fumes or other EHS issues during handling and processing of the primer and welding
- Good chemical/solvent resistance and UV resistance (due to low organic content and sol-gel based matrix)
- Good processability with fewer problems of settling, plugging of spray gun, etc. as compared to high zinc loading (70% and higher usually) primers used by industry today
Project Context and Objectives:
See attachment - Summary description
Project Results:
See Attachment - S & T result-foreground
Potential Impact:
The Weldaprime project has developed a zinc-free primer for steel with good corrosion protection and with weld-through capability (i.e. possibility to get good weld quality without removal of primer). This was achieved by keeping the organic content of the primer low and the specified primer thickness less than 25 microns. In addition to good corrosion protection (up to 72 hours in a neutral salt spray accelerated test, ISO 9227), the primer shows good weld quality (much fewer pores than organic primers and also the benchmarked zinc-free primer with aluminium flakes in it) and has minimal or no impact on cutting speed. No toxic fumes or other EHS issues were seen during handling and processing of the primer and welding through the primer.

In the absence of zinc providing galvanic protection, the primer depends on good barrier properties and good adhesion to the steel substrate. The primer shows excellent adhesion to steel substrates, which should prevent corrosion problems with undercut in the field. The barrier property of the sol-gel chemistry based primer matrix was further improved by the incorporation of suitably functionalised silica nanoparticles in the formulation (10% loading). However, further optimisation of the corrosion performance is needed to be best-in-class, like the zinc-rich inorganic silicate primers. This can be achieved not only by optimisation of the loading and functionality of the silica nanoparticles (improving the nanoparticle-matrix interphase) but also the possibility to disperse further additives able to re-passivate the bare steel surface once the coating might have been damaged. The use of cerium compounds or ceria nanoparticles, which has been mentioned in literature as providing some active inhibition effects, was tried during the project but while it showed some possible benefits for welding arc stability (see below), they did not have a positive impact on corrosion protection enhancement. However, various other commercial corrosion inhibition pigments (for e.g. triphosphates, phosphosilicates, etc.) could be used to further augment the corrosion protection possible with the Weldaprime primer, provided they do not impact welding performance and weld quality. This added active inhibition in addition to good barrier and excellent adhesion of the current Weldaprime primer will enable the consortium to exploit the results of this project to develop the next-generation Weldaprime zinc-free primer, which can be competitive concerning corrosion protection even with the best-of-class zinc-rich primers in the market.

The partners have identified 8 main advantages of the expected WeldaPrime product over currently available products:

1. Environmentally friendly alternative
2. Zinc free to reduce health hazards to welders
Durable corrosion protection avoiding any material or structural damage and cost incurred due to the damage
4. Superior scratch resistant comparatively for any mechanical damage caused during transportation to provide continuous protection to the steel surface
5. Saving time and cost on grinding or blast cleaning of steel before fabrication.
6. Saving cost on HSE
7. Good weld quality at first time
8. Provide good base for finishing protective coating ensuring that it does not blister due to adhesion failure.

The direct benefits derived from bringing the WeldaPrime product onto the market are:

• A high-quality preconstruction/shop primer on the market, offering good anticorrosion protection,excellent welding properties and good over-coating compatibility.

• More competitive primed steel being sold by a European SME, allowing savings (time, equipment) in steel transformation.

• Health benefits from use on non-toxic and non-polluting constituents.

Constructional steel has the largest share in the European steel market (145 M tonnes) with 27% (54 million tonnes), whereas structural steel represents 11% (22 million tonnes) in the same market.

According to British Constructional Steel Association just in the UK 8.6M tonnes is consumed while 9.4M tonnes are produced in the UK. It is important that European steel remains competitive in terms of cost and quality, and equally the shop-primer coating (or not) of the steel elements is a constituent of the cost versus quality equation. WeldaPrime will improve Europe's position for quality of product. The Western European market for coatings, including preconstruction primers, is regarded as being one of the largest and most mature in the world. In contrast, the Eastern and Central European markets are still regarded as being relatively small and "emerging". So export potential is very good. The global market for coatings is largely dominated by a handful of global companies representing over 90% of the preconstruction primer market. The WeldaPrime project intends to bring back to the European SMEs some of this market.
Adding to this and to strengths of the weldaprime primer, which are listed below, it is expected that the overall cost of welding could be reduced which would also bost and increase employability in Europe since the overall manufacturing costs would be reduced.
Strengths of the Wedaprime primer:

- Primer does not have zinc, this is directly related to all the welding fumes and EHS related matters, often discussed within the consortium and also within the proposal and DoW. There is EHS legislation around zinc and it is expected that in the future, which would benefit the Weldaprime primer, more restrictive legislation will appear regarding welding fumes and zinc dust.
- Improved product with respect to weldability: Weld-through (without removal of primer), minimal or no impact on cutting speed, good weld quality (much better than the organic primers and also the benchmarked zinc-free primer with aluminium flakes in it)
- No toxic fumes or other EHS issues during handling and processing of the primer and welding
- Excellent adhesion to steel substrate – should prevent corrosion problems with undercut
- Excellent top-coat compatibility to most commonly used epoxy type primers, for both as-applied and aged primer
- Good UV resistance, which is good for external storage (comparing with epoxy based will degrade with the sun)
- Should be able to withstand high temperatures due to low organic content, which facilitates, since there is little degradation of the primer with heat which is good for welding and thermal cutting which allows the parts to keep the coating protection, it also assist in pre and post heating
- No changes to procedure and kit used for applications (spraying) compared to what industry uses today.
- Ease of pre and post-processing which reduces cost of pre and pos-processing -- eg: no removal of primer before welding. (Not sure there is a way to quantify this advantage in terms of saved costs.
- Compared to high zinc-primers, the Weldaprime primers should be more easily handled at applicators as the high zinc primers are very viscous due to very high zinc dust content (unless diluted down with usually solvents like xylene, toluene, etc, raising EHS and VOC issues), prone to settling and hence need vigorous mixing before use, and also the high micron-sized zinc dust particles can lead to plugging of the spray nozzles and other issues.
- Good flexibility and so application around corners should be good/possible (whereas some zinc-rich primers are subject to “mud-cracking” and problems with flexibility because of the very high content of the zinc in the primer and very little binder


A demonstration of the weld-through capabilities of the WeldaPrime primer was carried out at TSM SL in Bilbao, Spain with support from TWI. A component was designed which demonstrates a typical application for the primer in ship building or steel construction. A scaled down component was chosen to that could be blasted, coated and cured using the equipment available to the project partners.
Prior to welding the demonstration components, as part of the tech-transfer to TSMSL, small test plates 250x100x8mm were blasted at TSM SL, coated and cured at LUR for welding trials to confirm the weldability of the primer and to develop final guidelines for the welding procedures. Welding trials were carried out jointly at both TSM SL and TWI Ltd following the guidance in EN17652 and partners agreed that the weldability was similar to the previous studies in WP5. These procedures were validated by TSMSL by testing of the welds at an independent test house in Bilbao. Fracture tests were carried out in accordance with EN ISO 9017 and EN ISO 9606-1 and no defects were observed in either test coupon and rather than fracturing in the weld, some toe samples fractured in the parent material demonstrating a weld stronger than the parent material. For some samples the coupon bent rather than fracturing, demonstrating good mechanical properties for the weld.
Micrographs of the welds showed very good weld quality. The independent test lab's inspection report noted that "Weld area is fine, showing a homogeneous weld seam disposition, HAZ and fusion area. No defects such as porosity, inclusions, slag, cracks etc. were found on weld metal.
Macroscopic aspects are fine".

Thus, this qualified welding procedure was then used to weld the demonstration components. Once again, the plates were first blasted at TSMSL, applied and cured by LUR and then welded using the same parameters as above. The welders noted very low fume, good weld bead quality (see Figure X3), and very low slag islands or slag splatter. The demonstrator was successfully completed with welding possible without removing the primer and producing a weld of high quality without excess fume or spatter. Very little damage occurred to the primer and the parent material remained protected close to the weld, with no obvious burning of the coating.
In summary, the demonstrator studies showed that the steel plates coated with the WeldaPrime primer could be welded without removing the primer, producing a weld of high quality without excess fume or spatter. Very little heat damage occurred to the primer during welding suggesting that corrosion resistance capability of the primer should be retained.

The results of the project were disseminated through several channels to raise awareness on the project. The project partners jointly carried out some of the dissemination while some of the dissemination was conducted independently by the partners. Typical technological dissemination of the project was trade fairs and similar while the scientific discoveries was disseminated at conferences and in journal publications.
The project partners together produced seminar material on the Weldaprime Primer including the necessary steps for applying it. The industrial demonstration case was also disseminated and use to attract the interest of the shipyard industry.
EWF organized the partners to create several versions of the flyer and poster with information on the project and what benefits the Weldaprime primer has.


The Weldaprime project produced scientific results. The main results of the project was presented at leading coatings and welding conferences. Some of the conferences and fairs where the results was presented is listed below:


International Institute of Welding (IIW) - Seul and Melbourne- The IIW Annual Assembly and Conference is the biggest conference in Welding, with more than 600 participants from around the world. By presenting the Weldaprime project in the IIW, presentation carried out by EWF, it was possible to engage with industry and academia

Poster and Presentation at At SMM Hamburg 2014 International maritime fair, offshore, Shipbuilding/shipyard industry

“ESEC 2014” - European Steel Environment & Energy Congress

EUROCORR 2015 conference

At Fair WASSER BERLIN 2015, International Leading trade fair for fields of water technology and waste disposal, valves, environmental protection, waste and raw materials management, sewage, renewable and conventional power generation

At Fair HANNOVER MESSE 2015 ,Leading Trade Fair for Renewable and Conventional Power Generation, Power Supply, Transmission, Distribution and Storage
NANOSMAT conference

Hannover Messe 2016

At Fair IFAT 2016 (Leading trade fair for fields of water technology and waste disposal, valves, environmental protection, waste and raw materials management, sewage, renewable and conventional power generation)
Eurocorr 2016: Weldable anticorrosion coatings for steel protection

The Weldaprime project was presented in other conferences and events in order to ensure engagement with academia and industry outside of the consortium.
Besides the conferences, some results were also presented in journals. Below are the published articles:

World Pipelines; Volume 14 Number 12 – December 2014

European Coatings Journal Q&A article on WeldaPrime January 2016

Q&A article - Anti-corrosive primer for steel protection – published in the Polymer Paint Colour Journal (PPCJ) • January 2016 edition

The full list of dissemination activities can be found in Deliverable 8.5.


A website about the project was produced at the start of the project and has been running during the duration. The website contains information on the project such as background on the project, the possible opportunities created in the project and how the beam tailoring is solved.

The website also contains News and Events, publications in the project and links to the project partners.

A YouTube video describing the application of the Weldaprime Primer was produced to provide fast and easily-accessible information on the use of the developed primer.

More information on the potential impact is given in Deliverable 8.5.

List of Websites:
Coordinator contact: