PROBLEM Using primers Inability of the weldable primer produced today to allow: Good Quality Welding Durable corrosion protection Without health hazards.

PROBLEM Using primers Inability of the weldable primer produced today to allow: Good Quality Welding Durable corrosion protection Without health hazards Not using primers Blast cleaning of steel Material waste Costs Sometimes too late

Primers Typical Anticorrosion Last max. 6 months Poor quality
Mechanical damage Too thick (~50 μm) Time consuming due to localised grinding required to remove the primer Thin enough (~25 μm) Allow welding Limited anticorrosion properties Zinc High % of Zinc Achieve the anti-corrosion properties but result in health hazards and discomfort Due to the zinc fumes released during the fabrication process CORROSION

Global production of steel ≈ 1400 M ton (1 trillion €)
Europe 145 M ton Structural Sector (16 M ton) Construction Sector (39 M ton) Carbon Steel Mild Steel Rest of the world 1255 M ton Corrodes at high rates

Aim ZINC-FREE corrosion protection primer Optimum thickness
Affordable cost Durable corrosion protection Resistant to mechanical damage Weldable without zinc fumes Aim

Main Purpose Anti-corrosion Durable and mechanically resistant
Self-repairable surface Optimum coating thickness Conductive material Minimise the by-products Odours or fumes Develop an anti-corrosion primer without any zinc content that lasts at least 1 to 2 years. Develop a durable and mechanically resistant primer formulation that is able to withstand damage through handling, storage and transportation. Provide a self-repairable surface to maintain continuous protection. Ensure an optimum coating thickness that maintains durable protection and weldability Ensure the formulation includes a conductive material that allows the arc to strike; thus avoiding any need to remove the primer before fabrication. Minimise the by-products that could affect weld quality or cause porosity Eliminate unpleasant odours or fume issues in the workshop Reduce the heat generated during the thermal cutting and welding procedures in the surrounding surface area. Conform to relevant legislations Provide good compatibility in relation to adhesion of an overcoat or final protective paint post fabrication

Partners

Specifications for the desired liquid primer:
Primers Zinc-rich organic Epoxy-base (with zinc poder/dust) Zinc-rich inorganic Silicates (zinc ethyl silicate/ zinc phosphate) Zinc free Sol-gel or silane-based Specifications for the desired liquid primer: Facile to deposit using existing spraying methods Compliant with structural steel grades Dries within 24 hours (preferably within 5 hours) Can be over coated with epoxies Corrosion resistance for more than 6 months (preferably 1 year) Mechanical robustness Thermal stability to 200ºC for 30 min Weldable with standard processes (MMA, MIG/MAG, FCAW and SAW) Low % Zn Not deliver the necessary performance High % Zn Low weldability Inclusion of impurities/ porosity ↓ Overall Weld Quality Galvanic protection Zinc-rich organic primers: Thick layer of zinc for galvanic protection -> good anto corrosion properties but poor weld quality Zin-rich inorganic primers: Thick layer of zinc for galvanic protection -> good anti-corrosion properties, but poor weld quality Zinc-free primers: Corrosion protection based on barrier and adhesion operation modes with sometimes some galvanic protection. The organic matrix may affect the weld quality Sol-gel or silane-based primers: Good performance, but solvent based. Limited industrial awareness and needs anti-corrosion properties to be strengthened Health & Safety issues Good anti-corrosion properties

modes of operation considered to achieve the desired properties
Adhesion based protection Galvanic Protection Barrier based protection One of the modes of operation is not enough to achieve the Welda Prime Chose at least two of the three presented

Candidates to perform the Benchmark activity
Sigmaweld 199 Hempadur 17360 Deoxaluminite

Benchmark Study process
Benchmark primers and substrate identification and supply Substrate surface preparation Primer deposition and curing CHARACTERISTICS OF THE CURED PRIMERS

Methodology for application and testing
Order Steel Surface preparation Primer deposition Primer curing Testing Before After Coating Performance Grades: S460 S355 S275 S235 Welding Performance Order steel: Grade chosen: S275 – after discussing with SMEs and SMEs-associations about relevant grades of steel and availability of these steels in the desired thickness Primer deposition and curing: Degreased substrates Rinsed with acetone Wiped with towel paper Ultrassonic bath 1 (alkaline agent) Ultrassonic bath 2 (tap water) Rinsed with de-ionised water Dried with hot air gun Primers were stirred and filtered through 400 μm paper filter Apply the primer (spray coating) Ventilated for 2 hours in the spray booth Cured at 24ºC for the times specified by the suppliers Testing: Adhesion Roughness Coating thickness Corrosion protection Thermal stability Mechanical stability Impact test Taber abrader test Mandrel test Testing welding and cutting: Welding tests Thermal cutting Welding fume 10 mm thickness 5 mm thickness

Summary of the welding and cutting tests
Hempadur 17360 Very poor weld quality High level of porosity Wormholes Badly for cutting performance Lowest cutting speed Deoxaluminite Well in the cutting trials Unacceptable level of porosity Very high level of zinc in the welding fumes Sigmaweld 199 Best during welding trials Cutting speed significantly lower than Deoxaluminite High level of Zn in the welding fumes Weldaprime should be: As weldable as Deoxaliminite As corrosion protective as Hempadur As performant as sigmaweld, but zinc-free

WeldaPrime Design Matrix Carrier Additives Water based Polysiloxane
Solvent based 100% solids Polysiloxane Epoxy or polyorethane Inert Active

Welda Primer SILICA ACTIVE COMPONENTS Matrix
ALUMINIUM FLAKES CERIUM COMPOUNDS ZIRCONIUM COMPOUNDS TES40 Corrosion protection coming via incorporation of nanoparticles in various formats Matrix based on epoxy-silane solution would be investigated in parallel Potentially need the incorporation of epoxy functionalised particles Good adhesion properties to the substrate Potentially shrinkage or crack Highly organic sol-gel matrix SILICA To be incorporated in the matrix to strengthen barrier properties Excellent barrier material Less expensive Few health issues ACTIVE COMPONENTS (corrosion inhibition) Aluminium flakes Iron nanoparticles Ceria Zirconia

Aluminium Flakes Cerium Compounds Zirconia
Aluminium has a lower potential than iron: Theoretical protection by the use of aluminium would be not as effective as the one provided by zinc Benchmark study: poor results when using Aluminium flakes Corrosion inhibitor Nanoceria – corrosion control Able to block the cathodic sited of the metal Positive influence on the mechanical resistance properties of coating when incorporated as nanoparticles Aluminium inhibitor properties are weakened because of the passivating aluminium oxide or aluminium hydroxide layers forming on the aluminium flakes. The aluminium flakes seem to affect weld quality significantly as was highlighted in the benchmark study Cerium Widely investigated as a corrosion inhibitor Nanoceria – unstable cubic fluorite structure lets ceria nanoparticles change their oxidation state releasing oxygen molecules and forming oxygen vacancies leading to promote the reduction or oxidation of molecules and contributing to corrosion control Able to block the cathodic sited of the metal, forming insoluble hydroxides and oxides on the surface

Primer prototypes formulation
Siloxane based Matrix Epoxysilane based Matrix Steps Matrix development Incorporation of nanoparticles The first step investigated by TWI and INM was to investigate the matrix system on its own, in order to develop a system that could cure and be deposited in such a way that it could be capable of leading to thick dry film thicknesses, while keeping the organic moieties to a minimum The next step of the work consisted of assessing the compatibility of the different nanoparticles with the matrices and then investigating some of their impact on corrosion protection properties in each of the two matrix systems

+ Siloxane based Matrix Silanes
Reduce Brittleness Improve adhesion to the substrate Low organic content due to organic compounds during welding which can contribute to: Inclusion Gas Release ⇒ pores in the weld Overall poor welding quality Need for a thin coating (<25μm) that is weld through Purely inorganic coating Not feasible ⇒ very brittle Not possible to achieve coatings over 1 μm + Deliverable 2.3. Matrix development As summarized, a sol-gel based inorganic matrix based on TEOS or its oligomeric form, TES40 was the starting point for a number of reasons, including low organic content due to organic compounds decomposition during welding which can contribute to inclusions, gas release leading to pores in the weld, and overall poor weld quality, the need for a thin coating (<25 μm) that is weld-through, etc. However, a purely inorganic coating was found to be not feasible because ti is very brittle and coating over 1 μm thickness could not be achieved. Hence, the addition of other silanes was considered in the matrix design to reduce the inorganic matrix brittleness and also improve the adhesion to the substrate.

Investigated reaction protocols
Investigated parameters: TES40: GPTMS ratio 𝐻 2 𝑂 ratio Catalyst type and ratio TES40 + 𝐻 2 𝑂+ catalyst GPTMS + 𝐻 2 𝑂+ catalyst Magnetic Stirring Magnetic Stirring Reaction times (0≤𝑡≤120 𝑚𝑖𝑛) Mixed Reaction time (0≤𝑡≤3 𝑑𝑎𝑦𝑠) Magnetic Stirring Deposition & Curing Characterisation REACTION PROTOCOLS AND PARAMETERS INVESTIGATED FOR THE MATRIX DEVELOPMENT

Incorporation of the nanoparticles Siloxane mATRIX
Silica Pyro-silica Nano-sílica Colloidal-silica Ceria Zirconia BEST PERFORMANCE Selected for further investigations SILICA Pyro-silica: Some agglomeration level Not lead to gelation Considered for further use When further tests were performed it was excluded as a solution because it presented agglomerations and poor adhesion to the substrate Nano-silica: Very good compatibility with TES40 Low level of agglomeration Partially functionalised BEST PERFORMANCE: selected for further investigation Adhesion 0/0 in the cross test before and after exposure to 150ºC for 24h Showing corrosion damages after more than 2 days of immersion in a 5% NaCl bath at 45ºC Colloidal-silica: Led the system to gelation No longer considered for further use CERIA Tendency to sediment after 30 min – not lead to system gelation Further investigations showed: Managed to dry Thinner DFTs when compared to other silica coatings Very poor adhesion Poorer corrosion properties ZIRCONIA Not lead to gelation of the system Kept for further considerations The investigation regarding the zirconia nanoparticles in the epoxysilane matrix showed very bad results, so it was not further investigated on the siloxane matrix After further tests performed:

Epoxysilane based Matrix
OPTIMISATION OF THE BASE MATRIX ↓ amount of water to slow down the reaction ↓ concentration of phosphoric acid + of epoxy resin araldite CY179CH1 to ↑ mechanical stability REDUCING THE CURING TEMPERATURE 130ºC (best curing temperature) to 80ºC (satisfactory curing temperature of the primer) Reducing the curing temperature: To facilitate the use of the primer by the costumer Lower curing temperature led to unacceptable micro-hardness values

GPTES TEOS Investigated parameters: ROR Value (ratio 𝐻 2 𝑂: hydrolysable group) Selection of filler material Concentration of filler material Addition of Epoxyresin Curing temperature REACTION PROTOCOLS AND PARAMETERS INVESTIGATED FOR THE MATRIX DEVELOPMENT + 𝐻 2 𝑂 + catalyst Hydrolysis/Condensation Addition metal complex Addition particle suspension Deposition & Curing Characterisation

Incorporation of the nanoparticles epoxysiLANE mATRIX
Silica 𝑆𝑖 𝑂 2 Nano-silica Ceria 𝐶𝑒 𝑂 2 Zirconia Added together in the base matrix GOOD CORROSION PROTECTION GOOD WELD QUALITY SILICA Better compatibility compared to zirconia in the base matrix Its concentration in the primer must be limited because it leads to increased viscosity – primer unapplicable using spray coating Best result against corrosion in neutral salt spray test NANO-SILICA - Good compatibility but high diluted primer CERIA Tends to sediment after some time Good compatibility with epoxysilane base matrix More stable arc formed during welding (better weld obtained) ZIRCONIA Agglomeration in all concentrations in the base matrix When Silica and Ceria were added together: Best results given for the lowest amount of ceria Less 𝐶 𝑒 3+ better the anti-corrosion properties

Metal Substrate S235 S-46 Panels S275HR
S275HR was selected by the WeldaPrime partners as the default substrate for the final deposition and full characterisation of the WeldaPrime primer Needs to be abrasive blated to an Sa 2,5 surface finish (minimum) with a roughness of at least 15 μm in order to represent the industry reality S235 and S-46 Panels were used in the lab scale development of the formulation (preliminary tests) – more accessible substrates S-46 Panels Standard low-carbon + cold-rolled steel + relatively clean/consistent/convenient/economical One of the faces – polished by grinding – so the mill surface was completely removed S275HR Used only after narrowing of the application and curing parameters with S235 substrates Degreased (substrates) Blasted sides of the substrates – rinsed with acetone Ultrasonic bath (alkaline cleaning agent) Dried quickly with hot air gun

Primer Deposition Method
Lab Scale Bar coating Spin Coating Industry Standard Spray coating Airless Spraying Paint Brush Bar coating: Depositing a line of coating solution on one side of the substrate and then pulling it across the substrate using a bar The deposition method seems reproducible and relatively homogeneous Spin Coating: Can coat only flat substrate with very little amounts of the primer Place the substrate at the centre of the rotating platform (adjustable rotating speed = angular speed) Drop the primer on the centre of the rotating substrate (spread on the substrate surface Fc) Thickness of the coating adjustable when changing the angular speed ↑ angular speed ⇒ ↓ thin coatings Defects observed mostly due to the substrate itself/insatisfactory curing conditions Results: Edges unhomogeneous – drawback of the process Notes: the solution dropped on the surface was pushed to the edges of the substrate by centrifugal force and accumulated there . Reducing the spinning speed would limit this effect, however it would lead to thicker coatings

Curing characterisation of coatings containing nanoparticles
CURING CONDITIONS Siloxane 150 ºC 1 hour Epoxysilane Curing Temperature Curing characterisation of coatings containing nanoparticles CURING CONDITIONS 1st graphic: Martens microhardness measurements, as a function of storage time, of the epoxysilane-based primer after curing at different temperatures 2nd graphic: Martens microhardness measurements performed on primer containing nanoparticles of SiO2 or ZrO2 compared to particle-free primer, measurement performed after spin coating of the primer and curing at 80 °C for 1 h 3rd graphic: Comparison of Martens microhardness of coatings applied using two deposition methods. The microhardness measurements were performed right after curing at 80 °C for 1 h. To validate the curing conditions and the coating quality the following tests were required: Microhardness Contact angle measurements

1st Candidate primer – Epoxysilane based primer
Substrate: S235 Deposition method: Sprayed Spray gun: SataJet RP – 1,4 mm Nozzle Compressed-air pressure: 1,25 bars Distance from the spray gun to the substrate: 20 cm Curing temperature: 80 ºC for 1 hour Optimisation of the base matrix 1. Reduce the amount of water 2. Low concentration of phosphoric acid Hydrolysis of GPTES and TEOS + phosphoric acid (catalyst) The optimisation of the base matrix is performed in a way that can allow to find a balance between Good shelf life Acceptable curing conditions Reduce the amount of water: decreasing of the ROR (ratio of water and hydrolysable group) (3.5 to 1.5). Decreasing the amount of water will slow down the reaction Low concentration of phosphoric acid – slow the hydrolysis/condensation at lower temperatures The chosen step to optimise the base matrix was the first one because it allows the slow down of the reaction and also entends the shelf life

1st Candidate primer – Epoxysilane based primer
10 wt% 𝑍𝑟 𝑂 2 in IPA – material from LUR – 10, 20, 30, 40 wt% particle in the primer solution 10 wt% Si 𝑂 2 in IPA (𝑆𝑖 𝑂 2 /𝑙) – material from LUR – 10 wt% particle in the primer solution 10 wt% Si 𝑂 2 in EtOH – material from LUR – 5, 10 wt% particle in the primer solution 4,3 wt% Stӧber Sphere (𝑆𝑖 𝑂 2 /𝐸) in IMS – material from TWI – 5, 10 wt% particle in the primer solution SELECTION OF THE FILLER MATERIAL/CONCENTRATION + 5wt% Epoxy resin Araldite CY 179 CH1 Higher concentration of filler material in the primer solution makes the Coating more stable Araldite will allow more stability against corrosion The highlighted formnulation is the one selected for full characterisation

2ND Candidate primer – Siloxane based primer
Extended shelf life Quickly cured after application (1-24 h) Pot A (TES40-silane mixture/NP) + Pot B (water/catalyst/solvent) Substrate: QPANELS cured at different temperatures Evaluation: Observed to identify any coating flaw Assessed if dry touch (ASTM D ) – if acceptable – measure thickness Adhesion to the substrate: cross-cut/tape test Corrosion resistance: immerse a scribed dip coated steel bar in a 3,5 wt% NaCl solution for up to 3 days Temperatures for the QPANELS curing: 90, 130, 150ºC Coating flaws: fish-eyes, cracks and peeling-off

PRELIMINARY SELECTION OF PRIMER FORMULATION
SILOXANE BASED PRIMER PRELIMINARY SELECTION OF PRIMER FORMULATION Matrix A1 No filler material TES wt% + acid catalyst Matrix B1 Silica NP Pyrogenic Silica Stӧber Silica Matrix A2 Basic Catalyst (𝑁 𝐻 4 𝑂𝐻) Acidic Catalyst (𝐻𝐶𝑙) Matrix A3 Matrix C1 Ceria NP Matrix B2 Matrix A1 TES wt% + acid catalyst Parameters investigated: Type of solvent: Ethanol/IMS/blend of both Two solventes with different boiling temperature => when curing, evaporate at different speeds => allow the coating structures to rearrange itself while curing => reduce stresses =>REDUCE CRACKING Boiling temperatures: Tb(IMS) = 78ºC Tb(IPA) = 82,5 ºC Tb(BuAcO) = 126ºC Molar ratios: 0,12/0,72/0,16 0,72/0/0,28 The blend of solventes => release stresses => can’t avoid cracking (5-20 μm Coating) Subsequent experiments => only one solvent => IMS (reasonable price/volatility/large industrial availability) Acidic catalyst Chose between: Hydrochloric acid (pka<1 => strong) → too agressive for QPANELS → some corrosion Acetic acid (pka = 4,75) → better results → no corrosion Amount of catalyst No significant conclusions could be drawn from these experiments Matrix B1 Pyrogenic Silica: Cracked white layers Shelf-life: 1 week Stӧber Spheres Transparent with a white haze Shelf-life: several weeks – room temperature or more than 2 months at 65ºC with no major change in viscosity Weaknesses of both: Poor adhesion Not prevent or limit the agglomeration of NP Matrix A2 Try to accelarate the hydrolysis and condensation reaction rates Attention: not so quick that can lead to gelation either on formulation or deposition Basic catalyst (𝑁 𝐻 4 𝑂𝐻) Increased viscosity when stirred for 1 hour at room temperature Gelation in 10 hours → time frame for deposition very restricted Cure for 45 min at 150ºC – dry to touch criteria Acidic catalyst (𝐻𝐶𝑙) Better stability once mixed: Slower increase in viscosity Better curing conditions (30 min/150ºC) Importance of the use of catalyst so hydrolysis and condensation reactions can occur at acceptable rates HCl – corrosion of the substrate Acetic acid – slow reaction rate Need to find another compound to the formulation in order to add some flexibility to the system and thicker systems to be deposited Matrix A3 Different ratios of TES40/GPTMS to evaluate the following properties: Adhesion Coating thickness Corrosion Resistance (immersion in 3,5 wt% NaCl solution Co-hydrolysis TES40 and GPTMS Betterr homogeneity Better adhesion than two Pre-hydrolysis TES40 and GPTMS Discarded for further experiments Results: TGF3 – corrosion TGF 2/6 – better performances in the neutral salt spray test Matrix C1 - Increased aglomeration of nanoparticles Matrix B2 Particles of nanosilica were added: To increase the Coating thickness To improve the barrier properties of the primer for better corrosion properties No gelation was seen during the time of incorporation of the sílica, formulation and its deposition as a Coating Excellent adhesion to the substrate Good corrosion properties

2nd Candidate primer – Siloxane based primer
10 wt% 𝑍𝑟 𝑂 2 in IPA – material from LUR – 10, 20, 30, 40 wt% particle in the primer solution 10 wt% Si 𝑂 2 in IPA (𝑆𝑖 𝑂 2 /𝑙) – material from LUR – 10 wt% particle in the primer solution 10 wt% Si 𝑂 2 in EtOH – material from LUR – 5, 10 wt% particle in the primer solution 4,3 wt% Stӧber Sphere (𝑆𝑖 𝑂 2 /𝐸) in IMS – material from TWI – 5, 10 wt% particle in the primer solution FINAL FORMULATIONS Full Characterisation Formulation 1: High in-homogeneity Poor adhesion No further characterisation Fromulation 2: Full characterisation

CHARACTERISATION OF THE PRIMER SOLUTION
Viscosity Surface Tension Siloxane 23,21 mN/m Epoxysilane 26,16 mN/m Solid Content gravimetric 34,7 wt% 24 wt% Viscosity: Measure using a rheometer with double gap cylinder T = 25ºC Both presented low viscosity Siloxane: constant viscosity independent of the shear rate Epoxysilane: decrease in viscosity with increase in shear rate Surface Tension: - Both presented a surface tension (ST) close to the ST of ethanol (the main solvent)

Characterisation of the dried films properties
Mechanical stability Adhesion & thermal stability Curing Roughness Coating thickness Corrosion protection NSS test Electrochemical characterisation Mechanical stability: Both show good abrasion resistance Adhesion & Thermal stability 150ºC – 24 h Lowest adhesion before and after termal exposure for the siloxane Curing characterisation - martens microhardness Epoxysilane presents higher microhardness than siloxane Varies with time – m,artens microharness increase with time indicating that the coating were still building a stronger network after 21 days Roughness High values Coating Thickness High variation due to the high roughness of the coatings Siloxane Coating were thicker than the epoxy silane Improved barrier effect for the thicker coatings Corrosion protection Electrochemical characterisation The substarates were immersed in two different solution Sol1. 3,5 wt% aqueous solution NaCl Sol2. Aqueous solution with 0,5 M NaCl e 0,05 M 𝐻 2 𝑆 𝑂 4 Degradation of both coatings Although the degradation is visible in both cases, both had a protecting effect on the steel substrate NSS (neutral salt stray) test Epoxysilane: 48 h exposure – the coating started to show beginning of failure 72 h exposure – cracks After drying – film started to peel off Siloxane: 24 h exposure – different signs of degradation (in comparison to the ones observed in Epoxysilane) 48 h exposure – cracked films were gone – CORROSION 72 h exposure – more visible corrosion

ARC WELDING PROCESSES MMA TIG MIG/MAG FCAW SAW

Process selection and test methodology
Welding Thermal cutting Welding fumes Welding process: MIG/MAG Fillet welding Steel plates blasted and coated 500 mm long 100 mm wide 10 mm thickness Thermal cutting: Oxy-fuel (acetylene) Welding fumes: collected on filter papers installed in a hood which collects fumes The filter papers are weighted before and after welding to assess the fume emission rate (FER) FER – calculated based on the fume weight deposited and the time for which welding was carried out The filter paper is also analysed for composition

Substrate requirements and preparation
S275 steel plates Uniform and abrasively blasted test pieces until 𝑆𝑎 2 1/2 Coated with shop primer The thickness of the shop primer shall be uniform Weld after a drying period of at least 10 days (10ºC – 40 ºC and humidity ≈ 50%) Preparation: Abrasive blasting (in house) → Ra ~ 15 μm - 6 axis OTC Almega A2 V20 series - Blast media: mix of chilled iron Wrapped in VCI paper Sealed in PE bags Surface cleaning and priming VCI – volatile corrosion inhibitor PE – poliethilene Coating and thickness should be in accordance with the supplier’s reccomendation

Conclusions VCI – volatile corrosion inhibitor PE – poliethilene
Coating and thickness should be in accordance with the supplier’s reccomendation

PROBLEM Using primers Inability of the weldable primer produced today to allow: Good Quality Welding Durable corrosion protection Without health hazards.

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PROBLEM Using primers Inability of the weldable primer produced today to allow: Good Quality Welding Durable corrosion protection Without health hazards.

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Presentation on theme: "PROBLEM Using primers Inability of the weldable primer produced today to allow: Good Quality Welding Durable corrosion protection Without health hazards."— Presentation transcript:

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