Yep, what about lead abatement, or ACM, or hexavalent chrome…excellent concerns deserving consideration, time and place early on in the process…

Should the presence of regulated substances be at issue, then concentrations, exposure pathways, risks, abatement, worker safety, waste management and other issues are / or should be discussed in planning stages of the project not while standing in the field with grit gun in hand.

Notes shared above focus on nut and bolt issues and experience associated with the technique intended to address the initial question “… thoughts on this type of blasting medium…”

Hope this helps.

Thanks,

JK

How do you separate the grit from the pulverized 'blasted' material? Water floatation or filtering? Seems to me you wouldn't want old paint, especially some kinds of primer, 'dusted' into the air even if eveyrone on the crew has full face shielding and respirators ... and that you would need VERY fine filtration and perhaps chemical reactive pads in your respirator, not just the 'typical' grit-elimination masks... even if it is 'wet when you handle it and blast with it.

If lead paint was involved, I would think you would have to tent the equipment and go negative air and have heppa filters in the exhaust. The same setup used for asbestos. I would think that it would be advantageous to use a medium that doesn't create a lot dust that would load up the filters too fast.

If there is a water filter that would take out lead, than using a pressure washer setup might be easier. You might not be able to recycle the grit.

We found grit could be recycled about five times before considered being fully spent. At that point, grains were noticeable smaller with a more rounded shape when compared to fresh angular material. Maybe a good comparison is sandpaper. Say you’re framing utility shelves using ¾” ply and use 80-grit paper on edges of freshly ripped boards – or whatever. After a while, that paper doesn’t feel as rough as it did when it was new. Grains glued to the paper have lost angularity. Likewise, as the grit impacts steel, it fractures and erodes losing its angularity and gets smaller.

Pulverized paint / rust form clay size material that increases in volume with each subsequent pass - which makes sense. Best analogy may be picturing a mix of sand and talcum powder. Each time the grit is recycled, there’s more talcum powder in the mix; however, the grit wore out before the volume of powder became a concern. As I recall, we started out with medium size grit. As it wears out, it takes more time to prep an area - guess one gets a feel for good grit verses spent grit.

We found there was no need for respiratory protection as grit is shot with water, not air. There is no dust while shooting. Simply put, at the end of a session, we’re pretty wet, but it made an otherwise dirty job bearable especially on a hot day. Having used other approaches, it was impressive prepping large areas as well as getting into nooks and crannies relatively quickly and with ease. We also experienced little to no dust when processing spent grit – we simply passed it through window screen overlaying 1/4-inch mesh to remove larger clips, flakes and other debris, etc.

Grit blasting may not work for every project – it takes a little thought, planning and practice – but it is a valuable tool that I’ve enjoyed using. Notes above are intended to cut through trials and tribulations to share experience, as needed. Hope this has helped answer some questions.

Thanks

Jim K

The key is planning - when in doubt TEST, TEST, TEST.

When not working on railroad projects, I’m an environmental scientist with 30-odd years of practice, including work in environmental assessments and clean-up.

When considering a project, be it a 50-ton car or 50-acre site, one must consider the potential for or evidence of environmental issues. If needed, samples are collected to determine the presence or absence of regulated materials, from that we can assess cost-effective ways and means to mitigate an environment issue, if needed.

If the presences of regulated substances are suspected, test to determine their concentrations and potential risk prior to formulating restoration efforts.

Thanks

Jim K

Perhaps I missed it in the detailed (and excellent) descriptions of the process, equipment, set-up, etc.

How do you deal with the use of water creating flash rust on what becomes bare steel? I have grit-blasted a number of rail cars and locomotives using Black Beauty slag, and the idea was to keep moisture away from the freshly-cleaned steel surfaces.

I have heard of "wet-blasting", and it usually seems to be used on non-ferrous surfaces (graffiti removal from concrete, etc).

Water + bare steel= rust. How do you handle that?

Thanks,

Howard P.

Exposure time is important. A cleaned area will rust over, but it took significant time to develop sufficient surface rust. A couple things come to mind.

We experienced slight oxidation (rusty haze) that developed while drying, but we never saw significant rusting. The whole area was wiped-off with clean rags prior to coating. As I recall, that removed haze as well as remaining grit, loose “dirt”, etc.

We typically waited for periods of good weather – a string of several days with no rain in the forecast. The sun and a warm breeze were a friend - water evaporates quickly from warm steel.

We also coated as soon as possible, usually the next day.

We researched our coatings and planned accordingly. I spoke with paint shop personnel at Steamtown and Strasburg to compare products and experiences during planning phases. The fella in the Strasburg paintshop was excellent to work with. We originally planned a 45-minute appointment – it went longer. I recall that we both had experiences with a 3-part roof coating system that produced mixed results; I think both gained from mutual experiences (war stories).

Back to the question, selected areas were coated with rust converter to prevent future problems. Can’t say enough about Benjamin Moore rust converter. It’s a little pricy, but does a great job.

We also used good, low VOC, industrial coatings that bond with base metal and built-up sufficient film. It took time and practice - technique evolves.

If “flash rust” is more than a light film; then something more may be happening. I’ve come across well and municipal water that was reducing; either slightly lower pH, higher sulphides or other condition that changes ferrous iron to ferric iron quickly. That’s one thing that comes to mind – maybe something else to look into.

Like most things, no one magic bullet, each job is site specific and good tools can be used the wrong way. I'll never forget one job – monitoring ACM abatement prior to demotion. While passing by a work bench, a saw a guy taking a break – he had carefully cut a hole in his full face respirator so he could still enjoy his smoke. I kid you not!

Thanks,

Jim K