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Surface Preparation Standards and Techniques                                                                     

 

Surface Preparation Before Application of epoxy coating.

Surface Preparation Standards

* National Association of Corrosion Engineers (NACE)

* Steel Structures Painting Council (SSPC)

* Swedish Standards (Sa,St)

National Association of Corrosion Engineers (NACE)

* NACE 1 White Metal Blast Cleaning
* NACE 2 Near-White Blast Cleaning
* NACE 3 Commercial Blast Cleaning

Steel Structures Painting Council (SSPC)

      * SP-1 Solvent Cleaning
      * SP-2 Hand Tool Cleaning
      * SP-3 Power Tool Cleaning
      * SP-4 Flame Cleaning
      * SP-5 White Metal Blast Cleaning
      * SP-6 Commercial Blast Cleaning
      * SP-7 Brush-Off Blast Cleaning
      * SP-8 Pickling
      * SP-9 Weathering Followed By Blast Cleaning
      * SP-10 Near-White Blast Cleaning

 

Swedish Standard (St,Sa)
* St 2 Hand Tool Cleaning
* St 3 Power Tool Cleaning
* Sa 1 Brush-Off Blast Cleaning
* Sa 2 Commercial Blast Cleaning
* Sa 2 1/2 Near-White Blast Cleaning
* Sa 3 White Metal Blast Cleaning
SSPC-SP-1

Solvent Cleaning

Removal of all detrimental foreign matter such as oil, grease, dirt, soil, salts, drawing and cutting compounds,and other contaminants from steel surfaces by the use of solvents, emulsions, cleaning compounds, steam or other similar materials and methods which involve solvent or cleaning action.

SSPC-SP-2
St 2

Hand Tool Cleaning

Removal of all rust scale, mill scale, loose rust and loose paint to the degree specified by hand wire brushing, hand sanding, hand scraping, hand chipping or other hand impact tools or by a combination of these methods. The substrate should have a faint metallic sheen and also be free of oil, grease, dust, soil, salts and other contaminants.

SSPC-SP-3
St 3

Power Tool Cleaning

Removal of all rust scale, mill scale, loose paint, and loose rust to the degree specified by power wire brushes, power impact tools, power grinders, power sanders or by a combination of these methods. The substrate should have a pronounced metallic sheen and also be free of oil, grease, dirt, soil, salts and other contaminants. Surface should not be buffed or polished smooth.

SSPC-SP-4

Flame Cleaning

Removal of all loose scale, rust and other detrimental foreign matter by passing high temperature, high velocity oxy-acetylene flames over the entire surface, followed by wire brushing. Surface should also be free of oil, grease, dirt, soil, salts and other contaminants.

SSPC-SP-5
Sa 3

NACE 1
White Metal Blast Cleaning

Removal of all mill scale, rust, scale, paint or foreign matter by the use of abrasives propelled through nozzles or by centrifugal wheels. A White Metal Blast Cleaned Surface Finish is defined as a surface with a gray-white,uniform metallic color, slightly roughened to form a suitable anchor pattern for coatings.The surface, when viewed without magnification, shall be free of all oil, grease, dirt, visible mill scale, rust, corrosion products, oxides, paint, or any other foreign matter.


SSPC-SP6
Sa 2

NACE 3

Commercial Blast Cleaning

Removal of mill scale, rust, scale, paint or foreign matter by the use of abrasives propelled through nozzles or by centrifugal wheels, to the degree specified. A Commercial Blast Cleaned Surface Finish is defined as one the from which all the oil, grease, dirt, rust, scale and foreign matter have been completely removed from the surface and all rust, mill scale and old paint have been completely removed except for slight shadows, streaks, or discolorations caused by the rust stain, mill scale oxides or slight, tight residues of paint or coating that may remain; if the surface is pitted, slight residues of rust or paint may by found in the bottom of pits; at least two-thirds of each square inch of surface area shall be free of all visible residues and remainder shall be limited to the light discoloration, slight staining or tight residues mentioned above.


SSPC-SP-7
Sa 1

Brush-Off Blast Cleaning

Removal of loose mill scale, loose rust, and loose paint, to the degree hereafter specified, by impact of abrasives propelled through nozzles or by centrifugal wheels.It is not intended that the surface shall be free of all mill scale, rust, and paint. The remaining mill scale, rust, and paint should be tight and the surface should be sufficiently abraded to provide good adhesion and bonding of paint.

A Brush-Off Blast Cleaned Surface Finish is defined as the one from which all oil, grease,dirt,rust scale, loose mill scale, loose rust and loose paint or coatings are removed completely but tight mill scale and tightly adhered rust, paint and coatings are permitted to remain provided that all mill scale and rust have been exposed to the abrasive blast pattern sufficiently to expose numerous flecks of the underlying metal fairly uniformly distributed over the entire surface.

http://www.amteccorrosion.co.uk/papers/surfaceprepguide.html

--Painting Failure--
 
Sagging                                    
 
 
 Sagging occurs when the Paint is applied in excess of the DFT specified, too much thinner has been added to the paint or the spray gun is held too close to the surface......more
 
 
Pinholes and Pores
 
 
 Using the wrong spraying technique, such as excessive air pressure, excessive film thickness, strong wind (too good ventilation) and too long application distance may cause craters, pinholes and pores......more
 
Blistering
 
 
 This is one of the most common typres of failure related to the adhension of the paint. Sometimes the blisterings are dry and sometimes filled with liquid......more 
 
Lifting
  
 Lifting is a raising of the undercoat. It is caused by a stronger solvent in the topcoat attacking the previously applied film......more 
 
Delamination/Peeling
 
 
 Loss of adhension to the substrate or between coats of paint is delamination or peeling......more
 
Orange Peel
 
Finely pebbled or dimpled surface texture with an appearance similar to the skin of an orange......more
 
 
 source of information from: www.jotun.com.my
 
 
 
 
 
 
 
SSPC-SP-8

Pickling

Removal of all mill scale, rust and rust scale by chemical reaction, or by electrolysis, or by both. It is intended that the pickled surface shall be completely free of all scale, rust, and foreign matter. Furthermore, the surface shall be free of unreacted or harmful acid or alkali, or smut.


SSPC-SP-9


Weathering Followed By Blast Cleaning

Weathering to remove all or part of the mill scale followed by one of the blast cleaning standards.


SSPC-SP-10

Sa 2-1/2
NACE 2

Near-White Blast Cleaning
Removal of nearly all mill scale,rust, rust scale, paint, or foreign matter by the use of abrasives propelled through nozzles or use of centrifugal wheels, to the degree hereafter specified. A Near-White Blast Cleaned Surface Finish is defined as the one from which all oil, grease, dirt, mill scale, rust, corrosion products, oxides, paint or other foreign matter have been completely removed from the surface except for very light shadows, slight streaks or the slight discolorations caused by rust stain, mill scale oxides, or light, tight residues of paint or coating that may remain. At least 95% of each square inch of surface area shall be free of all visible residues, and the remainder shall be limited to the light discoloration mentioned above.

source of information from :

 
 
 
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