Your Best Sandblasting Tips and Advice

OkieG · Feb 26, 2003

By the way...,
I want to say I have the utmost respect for the experienced members of this Board and the generous way they share their knowledge for the benefit of us all. My following comments are in no way intended to contradict information they shared in an earlier posts. They are just an observation I have made from my limited personal experience. And are presented as background for the questions at the end of this post.

Last summer I sandblasted some very rusty chunks of steel that eventually became rear wheel weights. I wanted to protect the shiny metal the sandblaster exposed, so I sprayed a good coat of Rustoleum Rusty Metal Primer. It's a "red" primer. I wasn't sure how well my method of attaching the weights to the wheels would hold up, so I decided not to topcoat with JD yellow until my welds proved themselves. Granted, it's only been about 7-8months, but the primer is adhering very well and there is no sign of rust at all. The welds are also holding up well, so I could have painted, but haven't gotten around to it, and didn't know that primer alone may not protect. The tractor sits outside all day, every day.

What do you think? It it still too early to tell if rust will show? Could some primers contain some of the substances refered to in earlier posts to chemically bind residual rust? Should I resandblast and reprime since the primer has been exposed so long? Just curious. Thanks.

OkieG

Anonymous Poster · Feb 27, 2003

Re-emergence of microporoscity rust is more common on sheet metal, especially stretched or shaped sheet metal, than it will be on heavy cast.
Rust also often emerges around welds, because there will be flex cracking, and poroscity. Rust can also occurr when a weld isn't thoroughly chipped. If you sandblasted post weld, you may not develope a problem.
Also, since you used RustOleum primer, it soaks and wicks into cracks, crevices and poroscity, unlike automotive primer, so you may have sealed problems off from oxygen.
For a set of wheel weights, I sure wouldn't reblast before painting the final coat. 5 years from now you may need to repaint the weights from routine bumps, scrubs and dings, and may need to reblast then.
If you have rust appearing from cracks or welds, you may just want to convert with either a phosphoric or tannic acid process, and then apply the final coat.
Sandblasting AINT a fun process, and I can't understand why anybody wants to do it. Wherever possible, I have switched to HP water and electrolytic rust removal, it's cheaper, it's cleaner, and I don't have to contend with sand problems.

OkieG · Feb 27, 2003

Franz,
Does the HP water you mention have sand in it??...like the wand attachment we've been eyeballing from Northern?

If electrolytic rust removal is cheaper and cleaner, I'm interested. Where can I find out more information? Did you say an auto paint store would know?

OkieG

DocHeb · Feb 27, 2003

Ted Kinsey gives a nice summary of the Electrolytic Rust Removal Process. Remember to use washing soda (sodium carbonate), use a plastic container, don't let the electrode and the object touch, and put the positive electrode on the electrode you're putting in the solution, and the negative terminal to the object to be cleaned. You're limited only by the size of your container and the amps put out by your power source.

djradz · Feb 27, 2003

Mine from Northern was almost the same, but I haven't used it yet. Only difference was mine was on sale for about $50 and had a metal wand not plastic. Everything else looks the same. Not sure if the one I got is even available but at $19.99 you can't go wrong. Hope it works out.

OkieG · Feb 27, 2003

ns-in-tx,
Oops! The wand pictured in Dourobob's post is a $19 unit. The unit at the top of the Sandblasting Kits page is a $50 unit that looks very similar. The $50 unit is the one I ordered (like djradz). Both are on the same Northern Tools internet catalog page. Sorry for the confusion.

OkieG

Anonymous Poster · Feb 28, 2003

Since I got back late, DocHeb posted a great link for electrolytic rust removal, so all I'm going to add to it is Don't Even Think About Using Lye, it doesn't offer enough process enhancement to compensate for the risks involved.
You can use either Arm & Hammer Washing Soda, (laundry asile) NOT Arm & Hammer Detergent, or get the soda from a pool suplier.

My HP water unit puts out 6000#, and it doesn't need sand added. Even 3000# units do NOT need sand added, what little is left behind can be removed other ways.
SAND is bad for use on tractors, cars, machines etc, because you NEVER get it all out of the machinery. Sand finds holes you never knew existed, and gets hung up in crevices.
Another bad thing about sand is the size of the granule, especially when compared to the size of the poroscity rust hides in. Water can get in tighter places, and at pressure is equally if not more abrasive, and water can be drained, leaving behind no abrasive residue.
Water under pressure can eat concrete from bridge decks, leaving behind nothing but shiney rebar. You do not want to get hit with water at pressures as low as 2000#, it HURTS and eats meat.

ns_in_tex · Feb 28, 2003

Thanks,

bgott · Mar 1, 2003

I know a guy here that operates a water jet to cut thick steel. He works in the chemical plants cutting holes in cracking units and pressure vessels that they don't want any flame around. It's been a while since he explained it to me but I think he said they sometimes use baking soda in the stream as an abrasive.