They reflect similar permissible levels of stains and tightly-adhered rust, mill scale and coatings, and can be summed up with a chart:. ISO is a visual reference and does not explicitly state percentages. The specifications specifically mention stains, streaks and shadows, but they are practically the same: a difference in color but of no discernible thickness.
Tightly adhered material refers to anything that cannot be peeled off with a dull putty knife. Surface preparations standards exist to maximize coating life and minimize costs.
White Metal is expensive to achieve, especially on maintenance jobs, and typically reserved for critical applications where the cost of failure is catastrophic. Near white is good enough for service in most severe environments. Commercial is less expensive and suitable for non-corrosive atmospheres and service environments.
Brush Off will save the owner the most money in the short run, if he can get away with it. When choosing a coating, the owner weighs the costs of blasting and painting against the risk of a premature coating failure. If the worst-case scenario is that he has to repaint in 5 years instead of 7, he might save money by cutting back from Commercial to Brush-Off.
Visible deposits of oil, grease and dirt must be spot cleaned prior to abrasive blast cleaning. The standards specify numerous methods for solvent cleaning. The most common method — and the least effective — is washing with soap, water and a rag. A dirty rag will also smear grease and oil: care must be taken to wipe, fold, repeat, and replace often. For large surfaces, pressure washing with soapy water is recommended, although soap residue will inhibit coating adhesion and should be rinsed off.
Brush Off is specified to remove loose rust, mill scale and coatings, and uniformly roughen up a surface in preparation for a new coat. Tightly-adherent materials are permitted to remain.
Brush Off is specified where the expected life of the coating is short, such as ship hull antifouling, or in mild atmospheres and non-corrosive service environments, such as the exterior of a tank, in a rural location. Industrial is specified for conditions when the existing coating is thin, well-adherent and compatible with new coating.
It is the most recent abrasive blasting standard, and not widely specified. ISO has no corresponding specification. Commercial Blast Cleaning specifies that all tightly-adhering matter must go. Commercial is specified when a high, but not perfect, degree of cleanliness is warranted. Near White is typically specified for high performance coatings over steel exposed to severe environmental conditions, such as chemical spills and fumes, high humidity, and proximity to salt water.
It is commonly specified for off-shore platforms, shipyards and other marine environments. White Metal is the highest grade of abrasive blast cleaning. No shadows, streaks or stains are permitted. When viewed without magnification, the surface shall be free of all visible oil, grease, dust, dirt, mill scale, rust, coating, oxides, corrosion products and other foreign matter. White metal is specified for steel serving under high temperatures, high pressures, and corrosive environments, and in cases where the catastrophic consequences of coating failure justify the extra expense, such as nuclear reactors, turbines, chemical tank linings, submarines, etc.
ISO is a pictorial standard containing reference photographs that illustrate what each blast specification looks like on a variety of rust grades and initial conditions. It comes in a hardcover A5 format that can be directly compared to the surface. Judging percentages of stains is an imprecise art that often causes rulers to come out. Preparing a job standard is a best practice for avoiding disputes:.
Surface preparation standards provide a basis for a service level agreement between blasters, contractors, inspectors and project owners. Knowing the standards are important for any abrasive blaster, and is a necessity for certified blasters. The specifications contain detailed methods and practices for preparing surfaces. They are frequently updated, so refer to them by name, date, edition number, and supplement when discussing project standards.
Thank you for contacting Graco. We have received your message and will contact you shortly. What you need to know to choose the right nozzle for your abrasive blasting application. Know the facts: there is no such thing as dustless or dust-free blasting in surface prep. A guide to calculating a bid that is designed to meet your target profit margin. Cookie Agreement Welcome! Yes, I agree to cookies Disagree. See Global Listing. Fine Finish Sprayers. Paint Sprayers. And application method, paint defects, what is the meaning of , for spray?
Hi Rani. The SA sand blasting standards are clearly I believe explained by Bijit Sarkar below, and there is a lot of detail on this thread. Hopefully it will help. We also have many threads here about spray painting, and application methods, and paint defects -- please try the search engine. Unfortunately your numbers "" and "" don't mean anything to me. Can you give us some context please? Please try to give us a couple of paragraphs about your situation.
We e-mail posters both when their question is posted and when they receive answers, but sometimes our mail just goes to their spam folder :- So we ask that you 'whitelist' mooney finishing. I need to know the technical details about the following- Surface preparation - Cast Iron part gratings, used for cooking ranges ; the surface needs to be prepared by sand blasting as per Swedish Standard, SA 2.
If it is possible then please inform about the surface finish value Ra, Rmax which can be achieved by the above mentioned process. I am also interested in the relationship between the SA standards SA 1, 2 2.
An interesting answer on your question which may be of help to me? Souren Paul , Laure Spriensma, Mr. Surface preparation standards are stipulated by various bodies throughout the world to designate the cleanliness condition of blasted steel, prior to applying a protective coating. The applicable cleanliness standard is usually called for by either the protective coating manufacturer or the owner of the structure to be painted.
Each standard is divided into four standards of cleanliness, broadly described as follows; brush off, commercial, near white metal, white metal. Whilst each standard may differ slightly in requirements and terminology the following cross reference chart indicates the close approximation of each level of cleanliness for each standard.
I hope the above info is useful to you. We are setting up a shipyard and are installing a plate preparation shop. May I know the surface profile difference between SA 2. Dear Mr. Shahaji Doltade We know that sa 2. Dear sir, I want to know about measuring instrument for surface finish SA 2.
I also want to know about from which size of grit we can achieve surface finish SA 2. Your sincerely. Hi, Prashant. The above discussions lead me to believe that Sa2. Do you have a copy of ISO handy, with its description of Sa2. Thanks for the information that SA 2.
Is it correct! You can't measure the things that are covered by Sa 2. Nor should we reasonably expect a given surface profile to consistently result simply by complying with a blast cleaning specification that is unconcerned about it, and which apparently permits the use blasting grit of any material, any size, and for any amount of time.
However, you can certainly specify both the Sa 2. Just as specifying that an automobile be red in color doesn't specify how many seats it must have, but you can certainly require both that it be red and that it have 5 seats. St 2: Thorough scraping with hard-metal scraper and wirebrushing — disc-sanding — etc. During the operation all the loose scale, rust and foreign matter should be removed. It should then have a faint metallic sheen.
St 3: Extremely thorough scraping and wirebrushing, disc sanding, power brushing etc. Surface preparation as for St 2, but considerably more accurate. After removing the dust, the surface should have a pronounced metallic sheen. Surface preparation grades marine.
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