Blasting Media and Primer Choice

[Jamie]

I have had a couple of quotes for blasting and priming my Austin Seven chassis. 

One proposes using iron oxide for the blasting with a powder coat primer (redox) which can be over-painted with a variety of paints. 

The other proposes to use either silicone carbide or crushed glass as a blasting medium with a high zinc content paint (I cannot remember the brand, but it started with a Z and was about 95 - 98% zinc).

Is either of these options preferable and, if so, why? My instinct says that the second option is better, but that is just a gut reaction.

Jamie.

[Davemayle]

Hi Jamie, I have blasted with both media. The chassis for my special was blasted with crushed glass and I sprayed it with a zinc based primer (Lechler Syntoprimer). Now has a few years of neglect and no problems. Chilled Iron is a longer lasting media but the particles will 'wedge' themselves into small gaps and almost impossible to remove. Not much of a problem with a 7 chassis.

[Jamie]

Thank you, Dave.

[Chris KC]

You pays yer money and takes yer choice - encapsulation coatings are great until they get damaged; once the surface is broken  moisture will slowly work its way beneath the paint towards an inevitable outcome. Sacrificial coatings (zinc) will corrode preferentially to the steel even if scratched; but some zinc primers I have come across are easily chipped, and they can be difficult to paint. My chassis was hot zinc sprayed many years ago and still seems pretty solid. I brush a fresh coat of black over it once every couple of decades.