Choice of Blasting Media and Finish

[JamieA]

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.

James.

 

[MetalMonkey]

Personally, I would avoid having the blaster apply a finish.
I've done it once before when i was being lazy, and ended up having to take it all off and redo it.

IMO, Ideally you would have the chassis blasted clean, and then you would apply an epoxy primer direct to the bare steel, that will give you the best protection.

 

[dave h 2]

Be aware of what you are getting. There are different levels.
From personal experience anything less that white SP5 will begin to rust again the next day, seemly growing out of the remaining dark rust pits.
Go carbide, It's heavier and sharper and multiple use. The iron based one is single use disposable and won't get into the rust pits properly.

 

[Dcal]

I agree with @MetalMonkey

Paint it yourself with an epoxy mastic, something like Jotamastic 90A.
If it is applied well it has a 20 year life in the marine splash zone, which is about as corrosive an environment you will get.
On your chassis you will never have to go it again.

If you apply a top coat within it's recoat time you don't even need to sand it before overcoating.
It can be applied with a brush or sprayed. I'd brush it to get into all the nooks and crannies and then spray all the easy bits, but given ths size of the chassis brush application would be absolutely fine.

The zinc rich primer offered is probably Zinga which is good stuff as well.

I wouldn't consider the powder coat primer without a lot more information.
One advantage of powder coat is you are less likely to "miss a bit" but that's it.

 

[brightspark]

get it blasted and coat up yourself then you will see how good a job is made of it . just make sure you coat it up as soon as possible in a dry warm place or it will flash rust

 

[Dcal]

Be aware of what you are getting. There are different levels.
From personal experience anything less that white SP5 will begin to rust again the next day, seemly growing out of the remaining dark rust pits.
Go carbide, It's heavier and sharper and multiple use. The iron based one is single use disposable and won't get into the rust pits properly.

Excellent resource @dave h 2

On this side of the pond we normally use the ISO standard which is the same but different.

Surface Preparation Standards Explained - SSPC/NACE & ISO 8501

Read on Graco why two dominant surface preparation standards through abrasive blasting, ISO 8501 and the SSPC/NACE joint standards, are tough to compare.

www.graco.com

 

[JamieA]

Thank you for the advice, which leaves me with a dilemma.

I see the value of coating the chassis myself, but I don't seem to get a lot of spare time and I would be concerned about it rusting again before I have time to paint it. Other than the garage, I don't have anywhere warm and dry that I can store it pending painting.

A bit of the devil and the deep, blue sea: a prompt paint job of unknown quality or do it myself, but risk rusting whilst waiting for me to get it done.

James.