Dry Ice Blasting

Dear Readers,

Wish You a Happy Winter, During winter let us discuss about surface cleaning with dry ice!
 
This new development is quickly expanding around the world. One system uses small rice pellets of dry ice shooting them out of the jet nozzle with compressed air.

Dry ice blasting is known by several names like dry ice cleaning, CO2 blasting and dry ice dusting. It is a kind of carbon di oxide cleaning, where dry ice in the solid form of carbon di oxide, is accelerated in a pressurised stream and directed in the surface in order to clean it. This method is similar to other forms of abrasive blasting such as sandblasting, or soda blasting substituted for dry ice as a blasting medium.

This method is superior to sandblasting because the dry ice is soft enough not to pit or damage the underlying surface. Since the dry ice evaporates completely as a gas it leaves no wastes. Only the material being removed must be disposed of.

Dry ice blasting is the superior alternative to sand blasting, short blasting, soda blasting, water blasting and hand cleaning.

Advantages of dry ice blasting:

·         No preparation required prior to cleaning
 

·         No need to dismantle machines for cleaning. The pellets easily reach into the smallest nooks and corners.

·         Minimal machine downtimes

·         Environmentally friendly cleaning

·         Without additional chemicals or spray agents

·         Surface are not damaged

·         No residues

Drawbacks:

1.   The loud noise produced requires protective ear equipment and may cause irritation to other people nearby. Although new machines are much quitter.

2.   Effective can only occur in a straight line of sight from the dry ice jet nozzle. Sometimes parts can be dissembled to help.

3.   Large amount of carbon di oxide are released which can be harmful if not ventilated out of space.

For More Details about Sand Blasting Click Here
For More Details about Surface preparation for Steel Click Here 

Surface Preparation- SSPC Standard

Dear Readers,

SSPC is a short form of Steel Structure Painting Council.

SSPC: The Society for Protective Coatings was founded in 1950 as the Steel Structures Painting Council, a non-profit professional society concerned with the use of coatings to protect industrial steel structures. SSPC creates, publishes and maintain standards for coatings that protect and preserve concrete, steel and other industrial and marine structures and surfaces. These standards address surface preparation, coating selection, coating application, environmental regulations and industry health and safety issues to the coating industry.
 

SP1 - Solvent Cleaning: The method of solvent cleaning is intended to remove “all visible oil, grease, soil, drawing and cutting compounds, and all other soluble contaminants from steel surfaces.” by cleaning with solvent, vapour, alkali, emulsion or steam.

SP2 - Hand Tools Cleaning: This standard covers the removal of loose mill scale, loose rust, loose paint, and other loose detrimental foreign matter from surfaces with the use of non-powered hand tools. Cleaning by chipping, scraping, sanding and wire brushing to a specific degree. Equivalent to ISO St2 Grade.

SP3 - Power tool cleaning: A mechanical method of surface preparation widely used in industry and involving the use of power sanders or wire brushes, power chipping hammers, abrasive grinding wheels, needle guns etc. Although usually more effective than hand tool cleaning, it is not considered adequate for use under severe exposure conditions or for immersion applications. Equivalent to ISO St3 Grade.

SP4 - Flame Clean: 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.

SP5 - White Metal Blast Cleaning: The removal of all visible rust, mill scale, paint and contaminants, leaving the metal uniformly white or grey in appearance. This is the ultimate in blast cleaning. Use where maximum performance of protective coatings is necessary due to exceptionally severe conditions such as constant immersion in water or liquid chemicals. Equivalent to ISO Sa3 Grade and NACE #1 Definition.

SP6 - Commercial Blast Cleaning: All oil, grease, dirt, rust scale and foreign matter are completely removed from the surface and all rust, mill scale and old paint are completely removed by abrasive blasting except for slight shadows, streaks or discolorations caused by rust stain, mill scale oxides or slight, tight resides of paint or coating that remain.

 If the surface is pitted, slight residue of rust or paint may be 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 the remainder shall be limited to the light residues mentioned above. Equivalent to ISO Sa2 Grade and NACE #3 Definition.

SP7 - Brush Off Blast Cleaning: A method in which all oil, grease, dirt, rust scale, loose mill scale, loose rust and loose paint or coatings are removed completely. Tight mill scale and tightly-adhered rust, paint and coatings are permitted to remain. However all mill scale and rust must have been exposed to the abrasive blast pattern sufficiently to expose numerous flecks of the underlying metal fairly uniformly distributed over the entire surface. Equivalent to ISO Sa1 Grade and NACE #4 Definition.

SP8 – Pickling: Complete removal of rust and mill scale by acid pickling, duplex pickling or electrolytic pickling.

SP9 - Weather and Blast: Weathering to remove all or part of the mill scale followed by one of the blast cleaning standards.

SP10 - Near White Blast Cleaning: In this method, all oil, grease, dirt, mill scale, rust, corrosion products, oxides, paint or other foreign matter have been completely removed from the surface by abrasive blasting, except for very light shadows, very slight streaks or slight discolorations caused by rust stain, mill scale oxides or slight, tight residues of paint or coating. Blast cleaning nearly to “White Metal” cleanliness, until at least 95% of the surface area is free of all visible residues. Equivalent to ISO Sa2.5 Grade and NACE #2.

SP11 - Power Tool Cleaning to Bare Metal: Utilizing same equipment as Power Tool Cleaning to remove all visible coatings and contaminants to bare metal substrate. It will be applicable where abrasive blasting is not feasible or permissible.

SP12 - Surface Preparation and Cleaning of Metals by Water jetting Prior to Recoating: Water jetting is the use of standard jetting from a nozzle at high pressures (10,000 psi or higher) to prepare a surface for coating. Intended primarily for carbon steel, but applicable on other metals, water jetting does not create a profile on the metal substrate. However, metals with an existing profile acceptable for painting can be cleaned with water jetting to expose the existing profile. Water jetting will remove all loose rust, loose mill scale, and loose coatings uniformly.

SP13 - Surface Preparation of Concrete: Describes requirements for mechanical, chemical and thermal methods of concrete surface preparation to improve the adhesion and longevity of coating systems. This standard applies to all types of cementitious surfaces including cast-in-place concrete floors and walls, precast slabs, masonry walls, and shotcrete surfaces.

SP14 - Industrial Blast Cleaning

SP15 - Commercial Grade Power-Tool Cleaning

SP16 - Brush-Off Blast Cleaning of Coated and Uncoated Galvanized Steel, Stainless Steels, and Non-Ferrous Metals.

Grades of Rust for Steel Structure

Dear Readers,

 

Rust is having important role to finalaise the surface preparation for steel structure before painting. Four Rust grades, designated A, B, C and D respectively, are specified. The rust grades  are defined as follows

 

Grade-A : It is mainly adhering mill scale, but little rust

Grade-B : It is rusting and flaking of mill scale has begun

Grade-C : The mill scale is rushing away, with slight pitting

Grade-D : The mill scale has rusted away, with general pitting

 

Rust Grade photographs are as follows

GRADE-A

 

Steel Surface largely covered with adhering mill scale but little, if any, rust.

 

 

  

 

 

 

 

 

GRADE-B

 

Steel Surface which has begun to rust and form which the mill scale has begun to flake. 

 

 

 

 

 

GRADE-C

 

Steel Surface on which the mill scale has rusted away or from which it can be scraped, but with slight pitting visible under normal vision.

 

 

 

GRADE-D

Steel Surface on which the mill scale has rusted away and on which general pitting is visible under normal vision.

 

 

 

For More Details about Surface Preparation of Structural Steel Click Here

 

Surface Preparation for Structural Steel

Dear Readers,

Effective life of coating of anti-corrosive paint applied to a steel surface is to a very large extent dependent on how thoroughly the surface has been prepared prior to painting.

 

Removing contamination and increasing surface roughness will allow maximum bond strength and adhesion to develop between coating and substrate. If the coating is applied to a well prepared substrate, they will have strong adhesion to that substrate and may be able to withstand these condition.

 

Coating performance is directly related to the quality of surface preparation.

 

Method of Surface Preparation 

1.       High Pressure Fresh Water Washing

2.       Solvent Cleaning or Degreasing

3.       Manual methods of Surface Preparation

4.       Power tool Methods of Surface Preparation

5.       Dry Abrasive Blasting

6.       Rotary or Wheelabrator blasting

7.       Slurry Blasting

8.       Hydro blasting

Blasting Standards

1.       ISO Standard (8501-1)

2.       Swedish Standards ( SIS 05 59 00)

3.       Steel Structure Painting Council Standards (SSPC-SP)

4.       British Standards Institution (BS4232)

5.       NACE Standards (National Association of Corrosion Engineers)

6.       JSRA Standards (Shipbuilding Research Association of Japan)

7.       Major Local Shipyard Standards