New approaches in corrosion protection
To protect steel constructions against corrosion, zinc containing primers have been proven to be of value.
Proven to be of value
In such formulations zinc is mostly available as zinc dust. The zinc pigments act as sacrificial anode, protecting the steel substrate against corrosion. With sacrificial anode conductively connecting to the steel to be protected, a primary cell is established. The steel to be protected acts as a cathode and the ignoble zinc as anode. Therefore, the current is flowing towards the steel to be protected. Instead of the steel the sacrificial anode emits their electrons to the oxygen, will be itself oxidsed and will become soluble. The generated zinc oxidation products contribute to the increase of the barrier effect. On the other hand, the usage of zinc primers causes different disadvantages.
Hazardous to water organisms
In order to achieve the cathodic corrosion protection, the zinc powder is highly concentrated in the primer matrix. To secure a good adhesion on the steel substrate under difficult conditions, the surface must be prepared very well and kept clean until the application is performed. For steel constructions, being located in polluted or marine atmosphere, this is either hardly to realise or at least very costly to achieve. If high effective zinc primers could be formulated with lower zinc contents, the higher amount of organic matrix could lead to a better adhesion of the primer on the steel substrate – as well as the adhesion of the medium and top coat to the primer. A further disadvantage of primers with high zinc concentration is that the zinc oxidation products are regarded as hazardous to water organisms. Also from this point of view high effective primers with lower zinc contents are highly desired.
As the effectiveness of the corrosion protection of the zinc is mainly due to the electrical contact to the substrate, the conductivity should be preserved as long as possible for a long-lasting corrosion protection, without promoting the abreaction of the zinc.
Modification of pigment composition
Within the publicly funded project “Zincpower”, it should be tested, whether a smart modification of the pigment composition can overcome the disadvantages and efficiency limitations of zinc primers. The following variations will be tested and eventually combined:
- Modification of the particle size and particle form of the zinc pigments
- Usage of zinc alloy pigments
- Surface treatment of zinc pigments
- Addition of zinc-free corrosion inhibiting pigments
Addition of graphene as inert pigment
Promising candidates for securing a good corrosion protection with reduced zinc pigment concentration could specially be graphene, which already provides with low pigmentation an improved adhesion as well as the preservation of the conductivity – and thereof the corrosion protection induced by the zinc – also in later phases of weathering. Additionally, the addition of graphene can enhance the wear resistance of coatings. Within the project, such a promising graphene pigment as well as the know-how how to incorporate into coating formulations is provided by the company The Sixth Element (Changzhou) Materials Technology Co., Ltd. (Jiangsu, China).
“Zincpower” – a project within Cornet
Partners: The investigations will be done at the research institutes IBDiM and IMPiB (Warsaw and Gliwice) plus at Fraunhofer IPA (Stuttgart).
German industrial partners are: Paul Jaeger GmbH & Co KG (Möglingen), Conmet GmbH (Aachen), Peter Kwasny GmbH (Gundelsheim), Lankwitzer Lackwitzer Lackfabriken GmbH (Berlin), Geholit+Wiemer Lack- und Kunststoffchemie GmbH (Graben-Neudorf), Mipa SE (Essenbach), Chemische Industrie Erlangen GmbH (Erlangen) and The Sixth Element (Changzhou) Materials Technology Co., Ltd. (Jiangsu, China).
Polish industrial partners are: Arma Firma Inżynierska Jerzy Noworyta Bartosz Noworyta Sp. j., Kraków; DAAS Sp. z o.o., Biała; DUHEN 2 Spółka, Olkusz; J.W – System Jacek Wojdyła, Szczecin; MALCHEM Sp. z o.o., Chynów; SPZP “Corrpol” Sp. z o.o., Gdańsk; Talkor Sp. z o.o., Gdańsk
Timeline: 1.5.2017 – 30.4.2019
German Sponsor: Bundesministerium für Wirtschaft und Energie via Arbeitsgemeinschaft industrieller Forschungsvereinigungen (Aif)
Cornet – transnational industrial collective research
Within Cornet actually six different European countries and regions voluntarily have affiliated themselves. The idea behind Cornet is to bundle national sponsorships and research initiatives in transnational projects and create synergies across different countries. It belongs to the sponsorship initiatives of Industrielle Gemeinschaftsforschung (IGFI).