BGAS Grade 2 Painting Inspector Course
BGAS Grade 2 Painting Inspector Course Fees 450 $ | BGAS Grade 2 Painting Inspector Course Exam Fees To be informed | BGAS Grade 2 Painting Inspector Course Duration 25 Days | BGAS Grade 2 Painting Inspector Course Location Muscat
Surface Preparation Methods and Standards
If the products of the corrosion reactions and other contaminants, were left on a substrate and paint applied over them, the adhesion of the coating and thus the coatings life would be far from satisfactory. BGAS Grade 2 Painting Inspector Course covers Surface preparation involves removing these contaminants and in some instances increasing the area available for adhesion by roughening up the substrate.
A good surface preparation grade (degree of cleanliness) along with a suitable surface profile can give 10 years life from a typical four coat paint system. The same system applied over a substrate with little or no profile and contaminant remaining might give four to six years, or even less.
Dry abrasive blast cleaning
Dry abrasive blast cleaning involves compressing air and forcing it along a hose and out of a small aperture called a nozzle. A pressure of 100psi results in the air exiting the nozzle at approximately 450mph. If abrasive particles are mixed in with the air and travel at the same speed, they will carry a lot of work energy.
This energy is used in chipping away millscale and other detritus from the substrate. With some abrasives part of the energy is used in shattering into small pieces and with others all the energy is used in impinging into the steel surface, roughening the surface and increasing the surface area to increase adhesion properties. Because all standards refer to the amount of contamination remaining on the surface, the longer the time spent on this operation, the higher the degree of cleanliness.
Sand
It is not permitted to use sand. SI 1657 states that any mineral used as an abrasive must release less than 1% free silica on impact. (Silica causes pneumonicosis or silicosis.) COSHH regulations do not allow the use of sand containing silica for dry blasting. Sand itself is perfectly safe, but shattering on impact releases silica which can be inhaled.
Copper slag
Although the name implies metallic content the amount of copper in the structure is extremely minute.
Minerals smelted with the copper, liquefy and form a protective cover over the molten copper to prevent reaction with the atmosphere like slag on a weld. When the copper metal is run off the slag is rapidly cooled in cold running water, which causes it to shatter.
The material is supplied in grit form (random, sharp edges, amorphous) and is very brittle, shatters into smaller pieces on impact and should be used only once and then discarded and so it is classed as expendable.
Garnet
A natural mineral classed as being of diamond type hardness, can be either expendable or recyclable. If the situation justifies, cleansing units are available to extract contamination so that the material can be reused, usually up to three times. Doesn’t shatter on impact but does suffer some wear, supplied in grit form.
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