Slurry Blasting Standards

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Slurryblasting Standards www.international-marine.com

Transcript of Slurry Blasting Standards

Page 1: Slurry Blasting Standards

Slurryblasting Standards

www.international-marine.com

October 2004

SL26/P

I4031

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Unless otherwise agreed in writing, all products supplied and technical advice orrecommendations given are subject to the Conditions of Sale of our supplyingcompany.

,International and all products mentioned in this brochure are trademarks of orare licensed to Akzo Nobel. © Akzo Nobel, 2004

International Paint Ltd, Stoneygate Lane, Felling, Gateshead NE10 0JY.Tel: +44 (0)191 402 2775 Fax: +44 (0)191 401 2320

www.international-marine.com

Page 2: Slurry Blasting Standards

Slurryblasting StandardsContents

1. Introduction2. Format3. Explanatory Text4. Procedure For Using The Standards

5. Notes6. References7. Visual Standards

IntroductionSlurryblasting is a technique for cleaning surfaces with a mixture of fresh water and abrasive where the elimination, or control of abrasive dust is required. Two slurryblasting systems are commonly encountered:

• Pressurised water abrasive blasting, which uses water to propel the abrasive.

• Air abrasive water blasting, which uses compressed air to propel the abrasive.

This visual standard has been prepared by using pressurised water abrasive blastingbut the photographs are representative of both preparation methods.

The surfaces produced by slurryblasting are initially identical to those produced by dryabrasive blasting because the abrasive cuts and deforms the metal surface producinga bright appearance. This bright appearance quickly changes due to ‘flash rusting’,which occurs when the surface drys off.

This visual standard has been prepared to help International Paint Technical Serviceand Technical Sales personnel advise on the recommended standard of slurryblastingand the acceptable level of flash rusting allowed prior to the application of ourproduct range. All surface preparation and coating application work is theresponsibilty of the applicator. All products and advice supplied are subject to ourstandard conditions of sale.

FormatThe standard consists of a series of colour photographs which depict the condition ofunpainted steel surfaces prior to and immediately after surface preparation byslurryblasting. It then shows these surfaces with varying degrees of flash rusting.

Explanatory Text

3.1 Initial Rust Grades

The standard illustrates two initial rust grades of steel from which the millscale hasrusted away. They are designated as grades C and D, and are comparable to the rustgrades C and D described in the ISO 8501-1:1988 surface preparation standard andthe SSPC VIS-1-89 surface preparation standard of the Steel Structures PaintingCouncil. The definitions are:

Rust Grade C: Steel surface completely covered with rust but with little, or slight pitting under normal vision.

Rust Grade D: Steel surface completely covered with rust, on which general pitting is visible under normal vision.

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3.2 Blast Standards

The standard illustrates grade C and D surfaces prepared by slurryblasting to twodifferent degrees of cleanliness. They are designated SB2 and SB21⁄2 and arecomparable to Sa2 and Sa21⁄2 described in the ISO 8501-1:1988 surface preparationstandard and to SSPC-SP6 and SSPC-SP10 of the Steel Structures Painting Councilsurface preparation standards.

The definitions are:

SB2 Thorough Slurryblast Cleaning

When viewed without magnification, the surface shall be free from visible oil, grease,dirt, most paint coatings and foreign matter. Any remaining contamination shall befirmly adherent.

SB21⁄2 Very Thorough Slurryblast Cleaning

When viewed without magnification, the surface shall be free from visible oil, grease,dirt, rust, paint coatings and foreign matter except for slight staining. Slight stainingshall be limited to light shadows, streaks or minor discolourations.

3.3 Degrees of Flash Rusting

The standard illustrates three grades of flash rusting. Light flash rusting, designated L,moderate flash rusting, designated M, and heavy flash rusting, designated H.

The definitions are:

L: Light Flash Rusting

When viewed without magnification, small quantities of light tan-brown rust willpartially discolour the original metallic surface. This discolouration may be evenlydistributed, or in patches, but it will not be heavy enough to easily mark objectsbrushed against it.

M: Moderate Flash Rusting

When viewed without magnification, a layer of light tan-brown rust will obscure theoriginal metallic surface. This layer may be evenly distributed or patchy in appearance,but it will be heavy enough to mark objects brushed against it.

H: Heavy Flash Rusting

When viewed without magnification, a heavy layer of dark tan-brown rust willcompletely obscure the original metallic surface. This layer of rust will be looselyadherent and will easily mark objects brushed against it.

Procedure for Using the Standard4.1 Select the photograph of rust grade that most closely resembles the rust grade ofsteel to be cleaned. Previously painted steel can be classed as either C or D grade,depending upon the degree of pitting. See note 5.1.

4.2 Select the photograph depicting the degree of cleaning that has been specified.For example, if the initial rust grade is D and thorough slurryblast cleaning is specified(SB2), use photograph D SB2.

4.3 Compare the prepared surface with the photograph selected immediately afterslurryblasting but before the surface has flash rusted to evaluate the degree ofcleaning. See note 5.2.

4.4 Prior to painting, compare the flash rusted surface with the flash rustingphotographs. For example, D SB2 L, D SB2 M, D SB2 H, to evaluate the degree offlash rusting that has occurred.

4.5 Check that the paint product specified is suitable for overcoating the degree offlash rusting that has occurred. See note 5.4.

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Notes

5.1 Painted Steel

The photographs in this standard were prepared from unpainted steel but they arealso suitable for depicting the appearance of painted steel after slurryblasting.

5.2 Inspecting Slurryblasted Surfaces Prior to Flash Rusting

When large areas are slurryblasted, flash rusting which obscures the original blaststandard may occur before an inspection can be carried out. Establishing the requiredstandard by blasting a small test area prior to the main blast may help, providing therest of the job is blasted to the same standard. Methods of ensuring the rest of thejob is blasted to the same standard will vary from project to project.

5.3 Chemical Corrosion Inhibition

Flash rusting can be prevented by the use of water soluble chemical corrosioninhibitors. These inhibitors may leave a crystalline layer on the steel surface as thewater evaporates which can then lead to a loss of adhesion and osmotic blistering ifcoatings are applied over this type of surface. International Paint do not recommendthe use of corrosion inhibitors to hold wet blasted surfaces. If inhibitors are used, theymust be thoroughly washed off with fresh water before International Paint productsare applied.

5.4 Removal of Flash Rusting

When flash rusting is too heavy for coating application, it may be removed or reducedby brushing with a hard bristle brush or by washing down with high pressure freshwater. High pressure washing will cause the area to re-rust but it is possible to reducethe degree of flash rusting from heavy to light using this method.

5.5 Removal of Wet Abrasive from Slurryblasted Surfaces

Wet abrasives will tend to stick to slurryblasted surfaces. This abrasive must beremoved prior to paint application. This can be done by fresh water washing or bybrushing the surface when it is dry.

5.6 Surface Profile

This standard makes no attempt to depict or define surface profile. However,slurryblasting will produce a surface profile similar to that produced by dry abrasiveblasting.

5.7 Soluble Salt Removal

This standard makes no attempt to define levels of soluble salts remaining onslurryblasted surfaces or to relate degrees of flash rusting to remaining soluble salts.However, all slurryblasting systems wash the surface as it is blasted and soluble saltlevels will generally be lower on slurryblasted surfaces than they are on dry abrasiveblasted surfaces.

References

6.1 Steel Structures Painting Council. SSPC-VIS 1-89‘Visual Standard for Abrasive Blast Cleaned Steel’.

6.2 International Standards Organisation ISO 8501-1:1988‘Preparation of steel substrates before application of paints and related products - visual assessment of surface cleanliness’.

Degree of Flash Rusting

D SB21⁄2 L: Light flash rusting

D SB21⁄2 M: Moderate flash rusting

D SB21⁄2 H: Heavy flash rusting

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Visual Standards

Rust Grade Standards

Rust grade C

Rust grade D

Preparation Standard D SB21⁄2

Rust grade D

D SB21⁄2 Rust grade D Slurryblasted to an Sa21⁄2 equivalent

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Preparation Standard C SB2

Rust grade C

C SB2 Rust grade C Slurryblasted to an Sa2 equivalent

Degree of Flash Rusting

D SB2 L. Light flash rusting

D SB2 M. Moderate flash rusting

D SB2 H. Heavy flash rusting

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Degree of Flash Rusting

C SB2 L. Light flash rusting

C SB2 M. Moderate flash rusting

C SB2 H. Heavy flash rusting

Preparation Standard D SB2

Rust grade D

D SB2 Rust grade D Slurryblasted to an Sa2 equivalent

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Preparation Standard C SB21⁄2

Rust grade C

C SB21⁄2 Rust grade C. Slurryblasted to an Sa21⁄2 equivalent.

Degree of Flash Rusting

C SB21⁄2 L. Light flash rusting

C SB21⁄2 M. Moderate flash rusting

C SB21⁄2 H. Heavy flash rusting

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Preparation Standard C SB21⁄2

Rust grade C

C SB21⁄2 Rust grade C. Slurryblasted to an Sa21⁄2 equivalent.

Degree of Flash Rusting

C SB21⁄2 L. Light flash rusting

C SB21⁄2 M. Moderate flash rusting

C SB21⁄2 H. Heavy flash rusting

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Degree of Flash Rusting

C SB2 L. Light flash rusting

C SB2 M. Moderate flash rusting

C SB2 H. Heavy flash rusting

Preparation Standard D SB2

Rust grade D

D SB2 Rust grade D Slurryblasted to an Sa2 equivalent

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Preparation Standard C SB2

Rust grade C

C SB2 Rust grade C Slurryblasted to an Sa2 equivalent

Degree of Flash Rusting

D SB2 L. Light flash rusting

D SB2 M. Moderate flash rusting

D SB2 H. Heavy flash rusting

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Visual Standards

Rust Grade Standards

Rust grade C

Rust grade D

Preparation Standard D SB21⁄2

Rust grade D

D SB21⁄2 Rust grade D Slurryblasted to an Sa21⁄2 equivalent

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Notes

5.1 Painted Steel

The photographs in this standard were prepared from unpainted steel but they arealso suitable for depicting the appearance of painted steel after slurryblasting.

5.2 Inspecting Slurryblasted Surfaces Prior to Flash Rusting

When large areas are slurryblasted, flash rusting which obscures the original blaststandard may occur before an inspection can be carried out. Establishing the requiredstandard by blasting a small test area prior to the main blast may help, providing therest of the job is blasted to the same standard. Methods of ensuring the rest of thejob is blasted to the same standard will vary from project to project.

5.3 Chemical Corrosion Inhibition

Flash rusting can be prevented by the use of water soluble chemical corrosioninhibitors. These inhibitors may leave a crystalline layer on the steel surface as thewater evaporates which can then lead to a loss of adhesion and osmotic blistering ifcoatings are applied over this type of surface. International Paint do not recommendthe use of corrosion inhibitors to hold wet blasted surfaces. If inhibitors are used, theymust be thoroughly washed off with fresh water before International Paint productsare applied.

5.4 Removal of Flash Rusting

When flash rusting is too heavy for coating application, it may be removed or reducedby brushing with a hard bristle brush or by washing down with high pressure freshwater. High pressure washing will cause the area to re-rust but it is possible to reducethe degree of flash rusting from heavy to light using this method.

5.5 Removal of Wet Abrasive from Slurryblasted Surfaces

Wet abrasives will tend to stick to slurryblasted surfaces. This abrasive must beremoved prior to paint application. This can be done by fresh water washing or bybrushing the surface when it is dry.

5.6 Surface Profile

This standard makes no attempt to depict or define surface profile. However,slurryblasting will produce a surface profile similar to that produced by dry abrasiveblasting.

5.7 Soluble Salt Removal

This standard makes no attempt to define levels of soluble salts remaining onslurryblasted surfaces or to relate degrees of flash rusting to remaining soluble salts.However, all slurryblasting systems wash the surface as it is blasted and soluble saltlevels will generally be lower on slurryblasted surfaces than they are on dry abrasiveblasted surfaces.

References

6.1 Steel Structures Painting Council. SSPC-VIS 1-89‘Visual Standard for Abrasive Blast Cleaned Steel’.

6.2 International Standards Organisation ISO 8501-1:1988‘Preparation of steel substrates before application of paints and related products - visual assessment of surface cleanliness’.

Degree of Flash Rusting

D SB21⁄2 L: Light flash rusting

D SB21⁄2 M: Moderate flash rusting

D SB21⁄2 H: Heavy flash rusting

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Page 14: Slurry Blasting Standards

Slurryblasting Standards

www.international-marine.com

October 2004

SL2

6/P

I403

1

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New ZealandNorthern IrelandNorwayPakistanPanamaPapua New GuineaPeoples Republic of ChinaPeruPhilippinesPolandPortugalQatarRepublic of IrelandRomaniaRussiaSaudi ArabiaSingaporeSloveniaSouth AfricaSouth KoreaSpainSri LankaSwedenTaiwanThailandTurkeyU.S.A.UkraineUnited Arab EmiratesUnited KingdomUruguayVenezuelaVietnamWestern SamoaYemen

Unless otherwise agreed in writing, all products supplied and technical advice orrecommendations given are subject to the Conditions of Sale of our supplyingcompany.

, International and all products mentioned in this brochure are trademarks of orare licensed to Akzo Nobel. © Akzo Nobel, 2004

International Paint Ltd, Stoneygate Lane, Felling, Gateshead NE10 0JY.Tel: +44 (0)191 402 2775 Fax: +44 (0)191 401 2320

www.international-marine.com