Surface Preparation By Blasting

Sand blasting has been banned in most of the areas due to the health hazard.

The surface finish required post blasting depends on the size of the particles.

UD15

I'd suggest a Wiki search first, then if you have relevant questions about specific topics, you might get some help here.

We can't infuse you with knowledge. You'll have to do some of the work yourself.

Sand blasting is used to remove material and does not change the surface properties of the metal being sand blasted, usually to remove rust/paint etc. By proper selection of the sand used, you can make sure you do not remove metal. Fine ground Nut shells can be used in a sand blaster to strip pain, but are to fost to strip away the metal.

Shot blasting, also called shot peening, is a way to treat the surface of a metal to increase its surface hardness. Not all metals can be shot blasted. Best to google it and read the details

Internationally the sand blasting is not only recommended but also forbidden to be used in steel surface preparation before applying the paints, and that is due to its dangerous on health because of the silica located at sand. Nowadays we use shot blasting or what we call grit blasting, which uses a grits come as a bi-product of iron mills, which haven't the dust or silica as located at sand.

Shot blasting (bead blasting) can give a compressive surface effect which enhances fatigue life. Sand blasting (or blasting with abrasive media that does not contain silica) gives a rough surface that is excellent for paint adhesion but does not give the same compressive surface effect, it may in fact reduce fatigue resistance

Blasting using a baking soda medium is used for striping paint from fiber glass. Easiest thing to do is call a commercial media blaster and inquire of them. They know what is used for what. The best media I have found for easily removing every thing except double-sided sticky tape from hard metals (not aluminum, copper, brass, etc.)is a carbide based medium. Its surface it all jagged edges and holds up well as long as the stripped material is separated if the medium is to be recirculated. It will remove the tape after a while but may erode a depression in the metal. Sand is still used in shops that use a fan to draw out the dust into a filtered enclosure. It is still the best for carefully frosting glass. Regardless of the medium, a respirator and balaclava as well as full length sleeves and pants (a cheap painters jump suit is a good idea) are the dress of the day.

See the attached thread http://www.surfacepreparation.com/catalog/wheel-blast-equipment.

People often confuse the grit (irregular shaped particles) blasting and shot (round or spherical) blasting accomplished in a tumblast or hanging type wheel blasting equipment with the peening or air motivated blasting techniques.

In the wheel blasting method the medium is accelerated by a wheel and propelled against the object. In sand blasting, whether employing sand, glass bead, walnut shells even solid CO2 particles, the medium is suctioned up by a nozzle and propeller by a gaseous flow often creating clouds of medium and removed material.

Since silica causes silicosis it is no longer acceptable unless a close capture system can be employed to capture the airborne particles.

Shot peening is a surface conditioning process that employs a round shot to actually deform and compact a metal surface often hiding surface defects or closing off openings that may lead to internal shrinkage defects which is why it is not allowed prior to fluorescent penetrant inspection.