It is important to understand that the VIS Guides only describes the pictorial standard and does not constitute the standard. It is to be used for comparative purposes and is not intended to have a direct relationship to a decision regarding painting requirements.
SSPC VIS has specified 9 different grades
In another article we have elaborated more extensively on the different surface preparation standards and how they compare to each other.
There are a couple of questions that we see coming forward from time to time.
I have a Specification that call for SSPC SP-X/NACE Y, what is my first step.
If you have a specification that requires abrasive blast, Hand tool, Power Tool or Water Jetting, make sure you have a copy of the standard specified. Unless otherwise stated in the specification, always use the most current version. If there is a VIS Guide applicable to the method being used, it is useful to have these on site. These can be purchased from the specifying organizations or from most Equipment distributors including myself.
I have a Specification that requires SSPS SP6/NACE 3, do I need to do SSPC SP1?
YES. All the surface preparation methods require removal of oil. Grease and other contaminants by SSPC-SP1 or other agreed upon method. If you do not clean the surface first, you do not meet the specification criteria.
The contractor says all the mill scale has been removed, but I think I still see some.
Mill scale usually fractures and breaks off during blasting and does not accept a profile. If there is any question, apply a couple of drops of 5% Copper Sulfate to the area in question, Steel will turn copper colored and mill scale will not.
I am arguing with the contractor over “staining” verses “rust”?
Rust is iron oxide that is attached to the surface of the steel and must be removed. If you have ever tried to get rust out of a shirt, you know that it can stain and does not come out easily. This can also happen to steel. A stain is part of the metal and can only be removed by removing the surface of the steel. Think of it like wearing a white shirt where the shirt is metal. You spill spaghetti sauce on your shirt, it is like rust. Remove the sauce by rubbing it with a wet cloth and you still have a red stain. It is OK to have the sauce stain just not the sauce.
As a last resort, you can examine the surface under magnification and determine if the stain is part of the surface or above the surface. A 10X magnifier or the 30X Pocket microscope works great for this as do the newer USB microscopes which also take pictures. (Note – the method states “viewed without magnification” so use caution when using magnification for what you are looking at).
I have a project that requires SSPC SP2 or SP3. Before I start, I cannot remove any rust, mill scale or paint with a Dull Putty Knife. Am I done?
NO. The dull putty knife test applies after the hand tool or power tool cleaning. Once the entire surface is clean, then check the surface with the dull putty knife.
Using Vis 1, the contractor says he has met the spec, I say he has not.
Remember, Vis 1 (and the other Vis guides) is a guide to help explain the standard. In case of disputes, the text of the method determines if the surface had met the specification. There are many factors that affect the appearance of the final blasted surface. Make sure you are using the proper starting grade for the metal in the Vis Guide.
Also, in the back of the Vis 1 Guide, it shows metal blasted to an SP5 with several different media. These all meet the criteria of an SP5 but they all have a different appearance.
My specification calls to use VIS 1 to determine surface profile. How do I do that?
You can’t. Surface profile has nothing to do with surface cleanliness. Prior to doing any work, this needs to be addressed and you may want to refer them to a Consulting Service since they should not be writing specifications.
Do I really need a “white metal” blast or is “near white” OK?
In general, you need a white metal blast for immersion surfaces, metalizing, and inorganic zinc. For most other services, near white is usually OK. The coating manufacturer should have the final determination of the required cleanliness. Also, on new steel, there should not be any difference between a white metal and a near white blast because there should not be any staining.
I need to achieve an SP 11 – What is the best way?
There are many considerations to determine the best method, but in general the Montipower Bristle Blaster easily achieves the 1 mil profile and generally 2.5 to 3.3 mils. It also gives the benefit of giving a profile that closely resembles that of a grit blasted surface.