The main purpose of the WELDAPRIME project is to address the above issues by:
Developing an anti-corrosion primer without any zinc content that lasts at least 1 to 2 years.
Developing a durable and mechanically resistant primer formulation that is able to withstand
damage through handling, storage and transportation.
Providing a self-repairable surface to maintain continuous protection.
Ensuring an optimum coating thickness that maintains durable protection and weldability (e.g. ≤25μm as per welding procedure standards for weldable primer)
Ensuring the formulation includes a conductive material that allows the arc to strike; thus avoiding any need to remove the primer before fabrication.
Minimising the by-products that could affect weld quality or cause porosity (e.g. Hydrogen, Nitrogen, Oxygen, ZnO, ZnCl2).
Eliminating unpleasant odours or fume issues in the workshop
Reducing the heat generated during the thermal cutting and welding procedures in the surrounding surface area.
Conforming to relevant legislations (e.g. VOC limits, REACH)
Providing good compatibility in relation to adhesion of an overcoat or final protective paint postfabrication.
The overall WELDAPRIME project aim is 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. The specific advantage of the WELDAPRIME primer over state-of-the-art primers is the delivery of high levels of corrosion protection simultaneously with good weldability, without the use of zinc. This zinc-free weldable primer will offer the following capabilities sought in weldable primers:
Good anticorrosion properties, offering excellent adhesion to substrate to minimise undercut, longterm protection (lasting 1- 2 years or more under Atmospheric Corrosivity Category 3 - medium: interior, high humidity, some air pollution; exterior, urban inland or mild coastal) and an ability to continue to provide protection following accidental breach such as scratches
Good arc weldability without further treatments (e.g. grinding and cleaning), preserving a stable arc strike; adaptable to automatic welding processes and allowing high quality welded joints to be generated
Good compatibility with overcoating
Good deposition compatibility and thickness control (e.g. using airless spray)
Cost effective as a preconstruction primer represents only 1% to 2% of the final cost of a steel
assembly, cost is normally not a major issue; however the overall cost must remain within the
same range, i.e. < €10/l
To achieve an understanding of the key chemical and nano-structural components necessary to allow a primer coating film to be developed. The key factors governing the adhesion to steel
substrate, corrosion resistance and weldability will be determined.
The design and fabrication of the primer coating film will be undertaken from a molecular
perspective using a sophisticated nanotechnology approach in order to develop a multicomponent
system with simultaneous structural, barrier and damage tolerance characteristics.
A key aspect of the project will be to look at the advancement of sol-gel technologies and the development of sol-gel derived materials to address the performance requirements from the perspective of coating manufacture, deposition, corrosion performance, weld-through characteristics and ultimately as a primer over which the final top-coat can be applied to the welded structure.
The overarching technical objective is to develop suitable molecular structures which incorporate the capability for excellent adhesion to the steel substrate, cohesive behaviour between the components targeted to provide protection, and good adhesion to the top-coat. The specific technical objectives are:
The development of low solvent content primer coatings which can be applied using airless
spraying and cure under ambient conditions. The solvent content limit will be less than 30g/litre if we develop a water-borne primer solution; it will be less than 350g/Litre of VOCs if we develop a solvent-borne system. The VOC levels will be in agreement with the European VOC
2010 legislation (2004/42/EC).
The development of primer coatings which provide excellent adhesion (of at least 20 MPa) to the steel substrates
The development of primer coatings with NO zinc either by a combination of prevention of undercutting, barrier properties, mechanical properties which minimise damage and the
incorporation of passivating components within the formulation.
The development of primer coating films which do not significantly affect the quality of welded joints.