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Bước 1: Kiểm tra độ ẩm của bề mặt Đây là bước quan trọng đầu tiên và không thể thiếu. Độ ẩm của bề mặt tiêu chuẩn là dưới 5%, nếu độ ẩm quá cao phải dùng dụng cụ chuyên dụng để xử lý như lớp vữa ngăn ẩm đối với sàn bề tông. Nếu bạn không xử lý thì hơi nước ở dưới sàn sẽ thẩm thấu ngược lên và làm bong lớp sơn. Bước 2: Xử lý và sửa chữa bề mặt Bề mặt bị yếu, hư hỏng phải được xử lý kỹ trước khi tiến hành tạo nhám. Tùy bề mặt sơn chúng ta dùng các dụng cụ tạo nhám khác nhau như: đá mài, giấy nhám, máy mài công nghiệp.. Bước 3: Vệ sinh trước khi tiến hành sơn công nghiệp Trước khi sơn công nghiệp chúng ta phải vệ sinh sạch sẽ bề mặt. Hút hết tất cả bụi và mặt để tạo độ bám dính và độ bền cho sơn.
Frosio course handout: Section 06 Surface preparation Pre-blasting preparation Frosio 06 Surface preparation slide # Pre-blasting preparation involves the following activities Rounding or smoothing of: Sharp edges Corners Welds Grinding of: Laminations Flame cut edges Weld spatter Notches minimum diameter: 30 mm Inspected and approved before cleaning See ISO 8501 “Visual assessment of surface cleanliness” Frosio 06 Surface preparation slide # Frosio course handout: Section 06 Surface preparation PrePre-blasting preparation Laminations, undercuts, welding seams Lamination Remove using grinder Undercut Undercuts exceeding classification ruling should be repaired by welding and grinding Manual weld bead Sharp profile peaks to be smoothed using grinder Frosio 06 Surface preparation slide # Steel preparation Weld spatter, welding smoke Weld spatter Weld Frosio 06 Surface preparation Areas at risk slide # Frosio course handout: Section 06 Surface preparation Steel preparation Edges and weld spatters Sharp edge Gas cut edge A Remove by grinder or disc sander A B B Rolled steel sections normally have round edges Therefore can be left untreated A A Remove visible spatter before gritblasting with grinder or chipping hammer B B For spatter not readily removed, remove using grinder/disc Weld spatter Frosio 06 Surface preparation slide # Grinding of sharp edges • Rounding of a sharp edge • Paint will not be able to give adequate film thickness over a sharp edge • Rounding the edge followed by stripe coating gives an even film thickness • This will improve the lifetime of the paint system Pre-treatment: Grind_paint_edge1 Frosio 06 Surface preparation slide # Frosio course handout: Section 06 Surface preparation Cross section of painted steel with a sharp edge • Paint applied with spray • Forms inferior coating thickness around the edge Paint Cd-4932-21 Steel Frosio 06 Surface preparation slide # Cross section of painted steel construction with well rounded edge • Paint applied by spray • Forms even thickness around the edge Paint Paint Cd-4932-20 Steel Steel Frosio 06 Surface preparation slide # Frosio course handout: Section 06 Surface preparation Grinding of sharp edges, welds etc Disc sander and disc grinder Sander for removing mill scale, paint and rust Grinder for heavy grinding, such as edges and weld beads Frosio 06 Surface preparation slide # Steel support prior to pre-blasting preparation • Sharp edges • Rust grade: A to B according to ISO 8501 Cd-4930-46 Frosio 06 Surface preparation slide # 10 Frosio course handout: Section 06 Surface preparation Disc grinding of a construction Even a small construction may have a of sharp edges Cd-4932-11 Frosio 06 Surface preparation slide # 11 Edge rounded with disc grinder A well rounded edge will ensure a sufficient paint film over the entire construction Cd-4932-12 Frosio 06 Surface preparation slide # 12 Frosio course handout: Section 06 Surface preparation Steel support after blast-cleaning to Sa ½ The sharp edges should have been rounded prior to blast-cleaning Cd-4930-47 Frosio 06 Surface preparation slide # 13 Steel support after blast-cleaning to Sa ½ The sharp edges have been rounded prior to blast-cleaning: Good ! Cd-4930-48 Frosio 06 Surface preparation slide # 14 Frosio course handout: Section 06 Surface preparation Pre-blasting preparation Grinding a small construction • Mark areas where grinding are required • Remove weld spatters • Grind the welds • Grind the notches • Important to carry out the grinding to improve the life time of the paint system Pre-treatment: Grind_construction1 Frosio 06 Surface preparation slide # 15 Early corrosion on sharp edge and spot welds • Paint has newly been applied • Exposed to wind and weather for approximately weeks Cd-4930-78 Frosio 06 Surface preparation slide # 16 Frosio course handout: Section 06 Surface preparation Insufficient pre-blasting preparation • Notch • Power tooling has been carried out • Sharp edge not grinded Cd-4932-16 Frosio 06 Surface preparation slide # 17 Grinding of notch with rotating file Easy access with a rotating file Cd-4932-18 Frosio 06 Surface preparation slide # 18 Frosio course handout: Section 06 Surface preparation Notch prior to pre-blasting preparation • Construction with notch must be grinded • Welding flux has to be removed • Sharp edges must be rounded Cd-4932-17 Frosio 06 Surface preparation slide # 19 Notches after blast-cleaning to Sa ẵ ã The sharp edges of the notches should have been rounded prior to blastcleaning Frosio 06 Surface preparation Cd-4930-49 slide # 20 10 Frosio course handout: Section 06 Surface preparation Dockmaster 3000 in action Frosio 06 Surface preparation slide # 131 Dockmaster 3000: good standard Frosio 06 Surface preparation slide # 132 66 Frosio course handout: Section 06 Surface preparation Painting the UHPWJ’ed area Frosio 06 Surface preparation slide # 133 UHPWJ robotic crawler: Joy-stick operated On a ship in drydock Tank farm: externally on storage tank Frosio 06 Surface preparation slide # 134 67 Frosio course handout: Section 06 Surface preparation Hammelmann – Spiderjet Use vacuum force to attach to the hull Frosio 06 Surface preparation slide # 135 Rust converters: Types of Rust-converters • Phosphoric acid based (Layer of iron phosphate on substrate) • Tannin based (Layer of iron tannate on substrate) • Penetrating oils • Systems transforming rust to Magnetite • Systems incorporating corrosion inhibitors • Other types may be available Frosio 06 Surface preparation slide # 136 68 Frosio course handout: Section 06 Surface preparation Rust converters: Surface preparation and painting • Light wire brushing is recommended for a majority of the products • Better surface preparation improves the performance • Wash the substrate before applying the paint (Otherwise: Excessive acids not removed) • Many types of coatings may be used on top • Thicker paint films improve service life Frosio 06 Surface preparation slide # 137 Rust converters: Experience • Rust may be only partly converted (Thick rust layers) • Some of the acids may remain one the surface • Salts in the rust will not be removed (Washing with fresh water is required !) • In some cases, poor adhesion to the coating • Blast cleaning or wire brushing give better performance of the paint system than rust converters Frosio 06 Surface preparation slide # 138 69 Frosio course handout: Section 06 Surface preparation CONCRETE Surface preparation • The surface preparation is a critical factor to achieve a long lasting performance • The pre-treatment is perhaps even more important than the application of paint • Always start the pre-treatment procedure by removing loose contaminants • Apply a penetrating primer coat, essential for a good result! Frosio 06 Surface preparation slide # 139 Concrete floors The laitance has to be removed, using: • Blast cleaning • Grinding • High pressure water jet • Wash with acid, followed by fresh water rinsing – This method contains a number of hazards, for which reason we are reluctant to recommend it unless it is carried out by an experienced professional contractor – Concentrated hydrochloric acid (33%)+ 1-2 parts of water CAUTION! Add acid to water – Rinsing + drying Frosio 06 Surface preparation slide # 140 70 Frosio course handout: Section 06 Surface preparation The benefit of using water jetting Low Pressure Washing (LPW)