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TECHNICAL > HELP > SURFACE PREPARATION

SURFACE PREPARATION

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A method should be chosen that:

1. Will provide the required Standard of Preparation
2. Will meet any of the limitations (dust free, no sparking, etc)
3. Is appropriate for the Area and the Environment

Some commonly employed techniques:

 

Cleaning Processes
BURNING: Torch is used to burn out impregnated oils from surface.

CONCERNS: Naked flame hazard.

 

DETERGENT / EMULSIFIER WASH: Solution is used to wash away Greases, Fats, Oils (normally impregnated). Machines are available that also "vacuum" the solution to aid drying.

CONCERNS: Disposal of washings. Moisture saturation of substrate.

 

SOLVENT DEGREASE: Solvents used to remove surface contamination, such as oil, fats, greases, chemicals and dust. This is normally a manual process.

CONCERNS: Solvent hazards (Fire & Toxic).

 

HARD SURFACE CLEANER DEGREASE: Solution used to remove surface contamination, such as oil, fats, greases, chemicals, and dust. This is normally a manual process.

STEAM CLEANING & PRESSURE WASHING: In pressure washing, solutions can be added to the reservoir tank, such as Fungicides and Degreasers.

Used to remove surface contamination such as oil, fats, greases, chemicals, and dust. May also remove rust and non-adherent coatings. Steam cleaning will also aid the release of soluble salts in steel.

CONCERNS: Disposal of washings. (If chemicals have been added to the reservoir). Moisture saturation of Substrate. (If porous). Moisture saturation of the atmosphere. (In enclosed environments). Splashing.

 

CHEMICAL STRIPPING: Non-abrasive method used to remove coatings. Such as paint stripper.

CONCERNS: Chemical hazards (Fire & Toxic). Disposal of washings.

Abrasive Processes
Most of these abrasive processes create dust or debris, which will need to be removed afterwards. Some of the machines can be fitted with vacuum devices which limits the amount of dust left of the surface, and stops dust and debris effecting the working environment. Any excessive surface contamination such as grease, oil, or fats, should be removed prior to abrading. Otherwise the contamination will simply be driven further into the substrate.

WIRE BRUSH: Removes loose rust and dirt. Manual or Mechanical wire brush is a "Minimal" preparation method, (only removes loose debris and rust).

SANDING: Removes dust and scarifies softer surfaces. Hand held machines available such as Disc Abrasion (DA) machines. Very slow in scarifying hard metals.

ANGLE GRINDERS: Removes rust and coatings, and scarifies hard metals.

NEEDLE GUN: Mechanical device where a series of small rods are used to rapidly hammer at the surface creating a pitted profile. Removes rust and loosely adhered coatings. Tends to be slow.

ABRASIVE BLASTING: "Blast Media" is fired at the surface at high speed. Many types of Blast Media are available, such as:

Chilled Iron Grit
Aluminium Oxide
Steel Shot
Glass Beads
Plastic Media
Ceramic Beads
Sand
Quartz
Sponge Media

The choice of media depends upon the Material being prepared and Standard of Preparation required. Can be used over a wide variety of substrates.

Removes rust, dirt, and coatings, and provides a "Blast Profile", even on hard metals.

Many different forms are available:

Enclosed Cabinets
Automatic Units
Hand Held With Extraction - Etc.

CONCERNS: Flying debris or Blast Media.

Abrasive Processes - Flooring
Abrasive Techniques that are used on floors warrant their own section, as there are numerous pieces of equipment that have been specifically designed to prepare the large areas that are commonly involved in flooring work. The equipment is also often manufactured in a smaller scale version for use on smaller areas or areas where access is difficult. Some of thee modified machines can be used on walls and roofs also.

BLASTING: "Blast Media" is shot onto the surface at high speed. This is a popular type of preparation. The Blast Media tends to be Steel Shot. Can be sued to prepare for practically all coatings, over a wide variety of substrates.

Removes rust, dirt and coatings, and provides a "Blast Profile".

CONCERNS: May have difficulties preparing certain substrates, or removing certain coatings, when the surface is "Rubberised".

Equipment supplier can advise on use of blast media for specific work.

 

PLANER (SCABBLER): Cutting Teeth are used to gauge way the top layer of the substrate. Used over most substrates, except on Float Screeds and Flag Stones.

Very efficient at removing coatings and preparing floors which are highly contaminated. Creates a GROOVED surface in the substrate. Cutting Cylinders (Barrels) with different Shaped and Sized teeth are available.

CONCERNS: The pattern left behind will remain evident after applying thin film or high build coatings. Only screed will easily disguise this grooved pattern.

 

GRINDING: High-speed rotary Grinding Disks scrape away top layer of substrate. Used on most substrates, except for Steel. Removes coatings and adhesives. Leaves a smooth surface, but may leave some shallow circular marking. Machine is moved from side to side as machine travels across surface. Assortment of disks available.

CONCERNS: Difficult for Grinding Disk to make contact with total surface area on floors that are uneven.

 

STRIPPING (PEELING): "Chisel" head scrapes away top layer of substrate. Efficient removal of most coatings, linoleum, carpets, bitumen. Limited use in preparing the surface of the substrate.

CONCERNS: Difficult for cutting tool to make contact with total surface area on floors that are uneven. After removing linoleum and carpets, the adhesive will be left behind.

Relative Working Rates
The working rates of these machines vary greatly depending upon substrate type, substrate quality, and the level of preparation required.
Preparation Equipment
Concrete
Steel
Floor Blasting - 250mm width
80 - 120m²/hr
20 - 40m²/hr
Floor Diamond Grinder - 250mm head
15 - 30m²/hr
--
Floor Planer - 200mm width
10 - 30m²/hr
--
Hose Vacuum Blast
--
3 - 5m²/hr
Open Hose Blasting
15 - 20m²/hr
7 - 10m²/hr
Open Hose Wet Blasting
15 - 20m²/hr
7 - 10m²/hr

 

Not Acceptable

Steel where mill scale has started to rust and flake
Brush off cleaning - SA-1
Commercial blast cleaning - SA-2

 

Acceptable
Best
Near-white blast cleaning - SA-2-1/2
White metal blast cleaning - SA-3
A SMOOTH surface is NOT the REQUIREMENT.

Select abrasives that can achieve the necessary standard of minimum depth of PROFILE at 3 mils (75 microns). The standards used by the industry are ISO 8501-1 Sa 2 1/2 = VERY thorough BLAST Cleaning. (US Standard NEAR WHIT FINISH SSPC SP10 - Swedish Standard Sa 2 1/2 SIS 05 5900)

Salt Water Applications

Metal surfaces that have been immersed for any periods in SALT SOLUTION (i.e. Sea Water), should be blasted to the required standard, left 24 hours to allow ingrained SALTS to sweat to the surface and then WASHED prior to a further BLAST to remove these. This process may be needed to be REPEATED to ensure the REMOVAL of ANY SALTS.

 

Concrete
Blast clean or MECHANICALLY scarify the surface to remove ALL loose materials and surface laitance. All old coating / paint / tar etc should be removed. Finished surface must be CLEAN & DRY. Wash old concrete down with detergent to remove any remaining OIL / GREASE / DUST. Use CLEAN water to wash away detergents &/or ACID from ETCHING the surface.

If NEW concrete application, allow 28 days to cure or until the MOISTURE content is below 6%.

Other methods of preparation that can be used if BLAST Cleaning is not available:

  • Grinding
  • Acid Etching (Hcl @ 4/1 with water - spread @ 1 liter per m2 - RINSE & DRY)
  • Hand Cleaning

NOTE: No STANDING water on application PRIOR to coating. DAMPNESS on substrate can decrease the physicals of the coating material.

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Fitness For Purpose Joint Design Surface Preparation Product Mixing
Application Curing Service Conditions Inspection / Touch Up
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