Sand Blasting

Sandbalsting before painting is required to ensure

[1] Removal of loose material e.g rust, millscale...

[2] Provide an acceptable surface profile for the bonding of the paint.

The degree of sandblasting is measured as SA 2.5, SA 3....and defined in a "colour chart" We generally settle on SA 2.5 for piping & structural steel requirements.

Sand blasting is one of the industries easiest means of metal preparation. Removing old paint, rust, scale,dirt, welding slag and splatter. It roughen the surface so that paint adheres better.

No its not necessary

It's not necessary. You just need to properly prep the old surface by cleaning any contaminants off that will effect paint adhesion. The paint adhesion will only be as strong as the weakest link.

Media blasting is a cheap fast way to restore a surface to look like new again. If you desire a professional looking job "do it!"

"what is its unit of measurement." Huh? I get sand in lbs, you can buy bags or buckets in different sizes. Most likely, you'll want to build or buy a blasting cabinet. You can reuse the abrasive and safe big $$$ plus generate a smaller mess that way.

Sand blasting is not the only way to prep metal.

I am restoring an old car. I had the same problem. I could not afford to have it done so, I opted to do it the old fashion way. Scraping and Sanding, using chemicals and sanding, Then I used a phosphate solution to clean the metal and to turn the microscopic rust back to iron. Then I used an epoxy paint to seal it.

Hi irpeck,

"I used a phosphate solution to clean the metal and to turn the microscopic rust back to iron."

Please expand on this.

-John

What kind of phosphate solution do you use to reduce trivalent iron to zero valent iron?

Which one of these did you have in mind guest?

You cannot be serious!

HI,

What is the field of application? In Industrial, Oil & Gas, cheimcal / power generation plants, housing etc?? the level of requirement and expectation may be different.

SA 3, 2 1/2, 2, St 3, St 2 or SSPC 5, 7, 10 etc are some measuring terms used by pictorial comparison to the BS / NACE SSPC stds. Is is important to remove the rust on the surface to avoid the new coat of paint from covering on top of it, or otherwise the rust, scale, blister or other defects will develop due to the changes environment; temperature, time and O2 contents.