Prepping bare metal question

['68 Coronet R/T]

I have used the Black Diamond but usually just for heavy metal items. It always has larger pieces that plug up the spray nozzle and therefore I run it though my screened funnel first.

For important work, the crushed glass is my choice. Also the crushed glass works fantastic in the sandblast cabinet as it doesn't fill it with dark dust.

 

[Lizer]

I use a fine mesh cooking metal strainer and strain the black diamond through that (I set it in a large funnel) to filter the black diamond like Coronet does. There are large pieces in there you need to filter out or they do plug up as mentioned.

Menards sells a media in the garden section, if you have it in your area. I think it’s a LOT cheaper than TSC. It’s around $8/bag.

 

[chevman]

Crushed glass has the right hardness for sheet metal.

 

[dhutton01]

I buy crushed glass at Northern Tool. It’s cheap if you buy a pallet of 24 bags. Life is too short to be recycling blast media. That and drilling spot welds.

Don

 

[Dave C 5]

Wish I had a Northern Tool nearby - saw their price on crushed glass , started to order some BUT $145 truck shipping !! It didn’t give me any cheaper options if I only ordered a few bags

 

[LITJOHN]

I buy crushed glass at Northern Tool. It’s cheap if you buy a pallet of 24 bags. Life is too short to be recycling blast media. That and drilling spot welds.

Don

Same here, that and walnut shells. Crushed glass for body parts, walnuts for motor parts and lite work.

John

 

[clubairth]

Yes another vote for crushed glass from Northern Tool. Cheap and it works very well. I have started using crushed glass INSTEAD of glass beads now. I find it works better and is cheaper.
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[chevman]

Crushed glass---glass beads. They are both glass, but they are different. Crushed glass has sharp edges for cleaning/removal, glass beads are smooth and rounded for polishing.

 

[crashtech]

I buy crushed glass at Northern Tool. It’s cheap if you buy a pallet of 24 bags. Life is too short to be recycling blast media. That and drilling spot welds.

Don

That's interesting, good to know! I'd been making a 4 hour round trip to the big city to get crushed glass, but the upside to that is that when I am headed that way it only costs me $8/bag (neglecting time and fuel of course).

I will second the assertion that glass bead =/= crushed glass, they are for different purposes.

 

[Chris_Hamilton]

Northern has gone up a lot on the crushed glass. 12.99 now. Less than 2 years ago I got it for 6.99 a bag. AFAIK my store didn't offer any discount for bulk. I'll ask next time I'm in there. Northern has coupons including a $50 off $250 one which can help offset the cost some.

 

[dhutton01]

Northern has gone up a lot on the crushed glass. 12.99 now. Less than 2 years ago I got it for 6.99 a bag. AFAIK my store didn't offer any discount for bulk. I'll ask next time I'm in there. Northern has coupons including a $50 off $250 one which can help offset the cost some.

Hi Chris. Buy it online for in store pickup. $8 a bag if you buy 24 bags if I remember right.

Don

 

['68 Coronet R/T]

The shipping costs have been the biggest deterrent from buying from Northern Tool. The nearest store to me is in El Paso, Texas and over 8 hours away.

 

[RosharonRooster]

Dang I thought the 45 min drive for me was far.

 

[theastronaut]

Another vote for blasting. I've been using Black Diamond in the red bag from TSC but I'll have to check out crushed glass from Northern, TSC has been slack on keeping red bags in stock.

As far as metal prep goes it just needs to be clean and have the correct surface profile for good mechanical adhesion. I like to leave whatever I blast bare for at least a few days to see if I missed anything in deeper pits, if so a light fuzzy layer pops back out of pits pretty quickly to let you know that you need to go over it again. It's not hard to miss a few small specs of rust when you're trying to blast a whole shell and your vision is a bit hindered by a dusty blast hood lens

I usually only immediately shoot epoxy on the areas where metalwork is already finished or isn't needed, or top coats aren't needed like behind door panels. I like to leave as much as possible bare for metalwork until a whole area is done metal-wise and is ready for fillerwork and build primer. No point in shooting epoxy on all of it and having to strip a lot off for welding, heat shrinking, etc. I also don't like shooting epoxy on areas that I won't be able to get to within the recoat window, there's no point in shooting epoxy just to have to sand it and shoot a fresh coat unless you're somewhere extremely humid. I've found that (at least here in upstate SC) *clean* steel doesn't really rust on its own unless all the rust wasn't blasted off in the first place. Fingerprint rust from handling will easily clean off with a wire brush on a drill, then go over the brushed areas with a DA for better adhesion. DA sanded areas can be wiped down without the rags shredding.

 

[Lizer]

^ this times a million.

 

[MikeK]

It's amazing how long blasted bare steel will 'keep inside .
I blasted a metal 4 leg step stool with the little 2 step pullout inside it. I was going to restore for my sister 15 years ago and uhh, didn't. I can almost epoxy and paint it today..
Guess maybe I should get it done now that it's on my mind.
My neighbor gave me a 5 gal. bucket of whatever the highway dept uses in stripping paint for reflection which I guess is crushed glass but just really bothered me from a health standpoint with just a respirator and cloth hood so I didn't use it.

 

[theastronaut]

It's amazing how long blasted bare steel will 'keep inside .
I blasted a metal 4 leg step stool with the little 2 step pullout inside it. I was going to restore for my sister 15 years ago and uhh, didn't. I can almost epoxy and paint it today..
Guess maybe I should get it done now that it's on my mind.
My neighbor gave me a 5 gal. bucket of whatever the highway dept uses in stripping paint for reflection which I guess is crushed glass but just really bothered me from a health standpoint with just a respirator and cloth hood so I didn't use it.

I've had some bare metal pieces stay outside for months without rusting, even after being rained on. There were some water spots that turned orange but for the most part it was still clean bare steel. It had been DA sanded to strip it.

From memory, I think it was Emory Motorsports that posted that they DA sand all of their bare steel projects with fairly high grit paper (400ish?) to keep rusting to a minimum during metalwork.

 

[MikeK]

Likely because you have "shallower pockets" for "water" to stand in I suppose.
Actually handling It with bare hands seems to cause most problems. Obvious from the "handling areas" on it.
I noticed on the stool today that the smoother surfaces are practically pristine where as the more rougher surfaces which had more extensive blasting will need reworked. That "pocket" thing I guess.
And incidentally All the mig repair welds,some ground smooth, are immaculate.

 

[crashtech]

Well, the SOP at our shop is to epoxy prime media blasted surfaces immediately. But we don't deal a lot with extensive metalwork, and when we do, we just sand the epoxy back a little to expose the area. I've been trained to take no chances with the initial primer step.

 

[crashtech]

I guess I want to add to this because I think it's important.

I think it's bad advice generally on this forum to say that it's okay to let bare metal sit around, because here on the forum we have people with all kinds of skill levels and all kinds of diligence levels. So I can see someone with limited knowledge of good procedure possibly using this advice to a disastrous outcome. To me, the initial primer on metal is THE most critical step in the paint job and can't be taken lightly.

I know I will might get some disagreement on this as to what was meant by proceeding posts, and maybe I am reading them wrong. But it just ought to be clear that primering metal is not something to mess around with.