Zinc Silicate Pre-Construction Primers Craig Henderson September 24 th 2009

Transcription

1 Zinc Silicate Pre-Construction Craig Henderson September 24 th 2009

2 WHAT ARE PRE-CONSTRUCTION PRIMERS? The Pre-construction primer is the first coat applied in ship construction The Pre-construction primer protects the steel from corrosion during the ship fabrication and construction process The Pre-construction primer is subsequently over-coated with the main primer system(epoxy A/C) at block stage

3 CORROSION PROTECTION DURING CONSTRUCTION

4 COATING APPLICATION Airless spray application

5 STEEL CUTTING PROCESSES Air plasma Submerged plasma

6 WELDING PROCESSES Semi-automatic Fully-automatic

7 MECHANICAL HANDLING/ STORAGE Primer must be mechanically robust

8 REDUCED SECONDARY SURFACE PREPARATION Primer must be overcoatable with minimal secondary surface preparation

9 KEY PERFORMANCE CHARACTERISTICS Corrosion protection White rust (zinc salt) resistance Heat resistance (welding/fairing operations) Reduced secondary surface preparation requirements Compatibility with shipyard fabrication processes

10 SOLVENT BASED PRE-CONSTRUCTION PRIMERS Applied at low film thickness - typically 15 m Low Solids - typically 20-30% volume solids High Volatile Organic Content (VOC) - typically 650g/litre Inorganic Zinc silicates the most common System of choice in high productivity shipyards - offers major advantages over IOE and PVB primers

11 SOLVENT BASED ZINC SILICATES 2 pack product pack 1(binder) pre-hydrolysed TEOS, solvents, water, acid catalyst pack 2 (pigment paste) zinc, extender pigmentation, solvent Level of zinc often varied to give required balance of corrosion resistance and welding characteristics

12 INFLUENCE ON PRODUCTIVITY Shipyards are constantly reviewing all technologies and seeking opportunities to improve productivity In order to improve productivity, attention must be focused on reducing the build cycle and re-work Several key areas are related to pre-construction primer technology: - Welding rate - Welding quality - Secondary surface preparation

13 WELDABLE PRE-CONSTRUCTION PRIMERS Weathering HIGH ZINC SILICATE HEAT RESISTANT ZINC SILICATE Excellent corrosion resistance Excellent heat resistance Excellent Weldability Excellent White Rust Resistance STANDARD LOW ZINC SILICATE IRON OXIDE EPOXY Weld Speed

14 HIGH HEAT RESISTANT PRIMERS Excellent welding performance Excellent cutting performance Super Heat resistance Excellent anticorrosion protection (6M) - even after heating Reduced production of white rust - even after heating Reduced secondary surface preparation requirements Proven shipyard productivity and cost savings

15 CORROSION PROTECTION AFTER HEATING High heat resistant primer Standard primer

16 WHITE RUST RESISTANCE High heat resistant Primer Typical Zinc Silicate Primer

17 WELDABLE PRE-CONSTRUCTION PRIMERS All pre-construction primers can be welded over depending on :- welding process welding rate defect acceptance criteria (shipyard standard) Define WELDABLE pre-construction primers as:- compatible with semi- automatic and automatic arc welding process (GMAW / FCAW/ SAW) at:- typical welding rates of inches/min ( mm/min ) with:- acceptable (?) levels of internal and external porosity

18 WELD POROSITY FORMATION Heat from the welding arc decomposes the primer into e.g.. H 2, CO, Zn Gases are trapped as the molten metal solidifies PIT WORMHOLE BLOWHOLE

19 FILLET WELDING Most susceptible to porosity formation contact with primer Second side is worst gases cannot escape hydraulic pressure primer blasted mild steel primer break 2nd side weld grind out 1st side weld

20 WELDABLE PRE-CONSTRUCTION PRIMERS High Heat Resistant 15 m (0.6 mil) dft RUTILE CORED WIRE NITTETSU 450mm/min (18 inches/min) METAL CORED WIRE ESAB TUBROD 600mm/min (24 inches/min)

21 WATER BASED PRE-CONSTRUCTION PRIMER

22 Market Drivers To reduce Volatile Organic Component s (VOC) Shipyards have two options:- Install abatement equipment on Pre-construction primer line Move to a waterborne Pre-construction primer 100,000 litres (26,417 US Gallons ) of solvent based Preconstruction primer/ year 75,000 litres (19,813 US Gallons) of solvent / year 65 tonnes of solvent / year There is a major requirement for a high performance zero VOC Pre-construction primer providing productivity, economic and environmental benefits

23 Alkali Zinc Silicate Coatings Poor Overcoatability Coatings available since 1930 s all based on alkali silicate binders Coatings provide many of the required Pre-construction primer performance attributes, but have one inherent flaw Blistering observed on overcoating/immersion Immersion in sea water for 1 month Alkali (Sodium, Potasium, Lithium) silicates are unsuitable for the major Preconstruction primer market

24 Alkali Zinc Silicate Coatings Poor Application Traditional water based zinc silicates cannot be applied by airless spray: zinc packing, wear, loss of pressure, both pumps and guns Partial success achieved using HVLP but Low pressure incompatible with many yard set-ups Poor quality of spray fan results in over application and inconsistent performance

25 Water Based Silica Sol Zinc Silicate Technology Silica Sol NEW TECHNOLOGY :- A novel coating concept Designed to overcome the inherent limitation of conventional waterborne zinc silicate coatings based on alkali silicate binders Osmotic blistering on overcoating/immersion Poor Application properties

26 Water Based Silica Sol Zinc Silicate Technology Physical Properties Attribute VOC Volume Solids Pot Life Application Drying characteristics H&S position Performance Zero 36% 4 hrs Airless Spray Dependent on T and air flow dry in <2mins (~solvent based) All materials registered No known H&S issues

27 Water Based Silica Sol Zinc Silicate Technology Application Properties Excellent airless spray application properties

28 Water Based Silica Sol Zinc Silicate Technology Corrosion Resistance - 6 months Felling (UK) Heat 800 C Water Based Silica Sol Zinc 15 m (0.6 mil) DFT

29 Water Based Silica Sol Zinc Silicate Technology Overcoatability in Seawater Immersion Cathodic disbondment (6m) Creep equivalent to Solvent Based Zinc Silicate No blisters observed 12m Immersion in seawater No blisters observed for any schemes Adhesion good for 8 schemes / 4 preparations tested Water based Silica Sol Zinc Silicate / Epoxy Topcoat

30 Water Based Silica Sol Zinc Silicate Technology Shipyard Performance 3 months Exposure

31 Tonnes solvent Tonnes solvent Preconstruction Water Based Silica Sol Zinc Silicate Technology Shipyard VOC benefit model Emissions comparison: Emissions from SP plant = 134 tonnes 19% of Total emissions Solvent Emissions in Tonnes Proposal: Emissions from SP plant = 0 tonnes 0% of Total emissions Thinner reduced by 18 tonnes Total solvent reduction = 152 tonnes (21%) Main Coating Schemes 69 Cleaner / Thinner Solvent Emissions in Tonnes 134 Shop primer Main Coating Schemes 51 Cleaner / Thinner 0 Water Interplate Based Silica Zero Sol Zinc Silicate

32 Zinc Silicate Pre-Construction Craig Henderson September 24 th 2009