Effect of Edge Preparation Methods on Edge Retention Rate of Epoxy Coatings

Transcription

1 ISST-2007 Effect of Edge Preparation Methods on Edge Retention Rate of Epoxy Coatings S.S. Seo,, M.K. Chung, C.S. Park, C.H. Lee and K.K. Baek Hyundai Heavy Industries Co., Ltd.

2 IMO s s PSPC 2 Water Ballast TK Epoxy HB (160 μm) Epoxy HB (160 μm) I.O.Z. (15 μm) m) Steel Performance Standard For Protective Coating

3 IMO s s PSPC 3 Corrosion Control of Water Ballast TK: Steel Thickness Protective Coating Sacrificial Anode Maintenance

4 IMO s s PSPC 4 1 st ITEM D.F.T. D.F.T. Measurement st, 2 nd Surface Treatment Erection Joint Edge Preparation Edge Stripe Coating (S/C) Dust Soluble Salt P S P C 2-Coats, 320 μm m NDFT(90/10) Annex 3, Avg. 3~4 points/10 m 2 Sa 2.5 Blasting, Profile: 30~75 μm Welds, Damaged Area <2%: St 3(Grinding) 2R, or 3-Pass 3 or at least equiv. Min. 2 S/C; proven weld seams 1 S/C Brush, Roller (Specified area only) Size [5],[4],[3]: remove to Rating [1] Size [2],[1],[0]: remove if visible on steel <50 mg/m 2 NaCl, Bresle,, Min. 1 Point/Block

5 IMO s s PSPC Basic coating requirements Table Secondary surface preparation The steel surface shall be prepared so that the coating selected can achieve an even distribution at the required NDFT and have an adequate adhesion by removing sharp edges,, grinding weld beads and removing weld spatter and any other surface contaminant. Edges to be treated to a rounded radius of min. 2 mm, or subjected to 3 pass grinding or at least equivalent process before painting.

6 Background 6 IMO s s PSPC : 3-Pass or 2-R 2 edge grinding treatment Negative, side-effect effect : - DFT tend to be thicker than flat areas - More vulnerable to coating cracks Practical edge preparation methods? - Several Practices - Cross sectional measurement of DFT at Flat/Round area (Edge Retention Rate, %)

7 Experimantal Methods 7

8 Experimentals 8 Preparation of Specimen/Spray Coating Edge roundness condition: Flame cutting, R=1mm, R=2mm, R=3mm, RC Measurement of Roundness at Edge (HHI Yard Practice) - RC : One Pass Grinding + Burr Removal (Sand Paper) - Automatic Edge Roundness M/C - RC Cutter Cross-sectional sectional observation of D.F.T. Evaluation: Edge Retention Ratio, Edge Roundness

9 Edge Retention Ratio (ERR) 9 E2 E1 Top coat Primer coat Steel Plate F2 F1 T3 ERR(Primer) ) = E1/F1 ERR(Top coat) = E2/F2 ERR(%) = DFT(Edge) DFT(Flat)

10 Edge Preparation (1) 10 RC (1 Pass grinding + Sand Papering) Automatic Edge Roundness M/C 45 ± 10

11 Edge Preparation (2) 11 RC Cutter Rolled Plate

12 Coating Materials 12 Type Thinning Product A Pure epoxy (Tar Free) 5 % Product B Modified epoxy (Tar Free) 5 % Color Grey/Light Grey Bronze/Aluminum Specific Gravity Viscosity (cp( cp/ku) (0% Thinning) Solid Vol. Ratio (SVR) 1.5 kg/l 1,237/ % 1.25 kg/l 1,103/ %

13 Coating Sample Preparation 13 Spray coating RC Flame cutting abt : 1mm R = 1 Stripe coating abt : 2mm R = 2 abt : 3mm R = 3

14 Results & Findings 14

15 Coating Thickness Effect 15 Sharp Edge One C Grinding D.F.T. Increase Outer Surface Radius Increase

16 Crack Tendency w/ D.F.T Edge Cracking after 4 Point Bending Test - Crack width varies directly as coating D.F.T. - Initial crack site varies inversely as coating D.F.T. - Number of crack: Thin coating > Thick coating - Crack Width: Thin coating < Thick coating

17 Edge Roundness Effect 17 Edge Retention Ratio(% Coating Mater ial A Before Blasting After Blasting Increasing Rate 0 Sharp Edge C RC R=1 R=2 R=3

18 Edge Roundness Effect 18 Edge Retention ratio(% Coating Mater ial B Before Blasting After Blasting Increasing Rate 0 Sharp Edge C RC R=1 R=2 R=3

19 Edge Blasting Effect 19 Before Blasting After Blasting

20 Stripe Coating Effect 20 Edge Retention Ratio(% Spray Spary & One Stripe Increasing Rate Sharp Edge C RC R=1 R=2 R=3

21 3-pass Grinding 21 3 Pass Grinding 45 ± 10 R = 2.0 mm

22 RC or Edge Rounder 22 RC (1 Pass G/R + Sand Papering) Automatic Edge Roundness M/C R = 2.0 mm R = 3.5 mm

23 RC Cutter or Edge Roller 23 RC Cutter Rolled Plate R = 2.0 mm R = 2.75 mm

24 Roundness Summary 24 4 Edge Roundness(mm R = 2mm RC RC Cutter Rolled Plate 3 Pass Grinding Edge Roundness M/C

25 Conclusions Variation of coating D.F.T. at the edges with different roundness were measured. 2. Equivalency for R = 2mm or 3 Pass grinding - RC(One Pass grinding + Sand Papering) - Automatic Edge Roundness M/C - RC Cutter - Rolled Plate

26 Thank you! 26