I’m brand new to the post, but I’ve read enough of these in the magazine to know that you all are a relatively civil bunch. Or so I hope. Your ability to control yourselves and maintain your composure will come in handy when I tell you what I did.
I have a Delta contractor’s saw with a cast-iron wing – shiny, silvery, professional. I wanted to clean oxides off of some vintage metal door hardware and chose muriatic acid as my weapon. I placed a cardboard flat (like the half boxes that cases of sodas come in) upside down on the top of my shiny, silvery, professional cast iron table saw and extension (it was the most convenient horizontal surface in my “corner of the basement” shop) to keep any acid separated from the shiny, silvery, professional table top.
I used a series of workshop paper towels to clean the hardware (worked like a champ!) and, after use, placed most of them in a separate container away from the shiny, silvery, professional table top. However, when I was done, I inadvertantly left one of the paper towels on top of the upside down cardboard box, which remained on top of the shiny, silvery, professional table top.
Overnight, the muriatic acid seeped through the cardboard box, and without dripping onto my shiny, silvery, professional table top, attacked said table top through a fuming process, much like ammonia attacks oak in a fuming box. To my horror, the next time I looked, my shiny, silvery, professional table top had become a dull, spotted, and seemingly anodized table top. No longer professional. No longer happy.
I tried to rinse with water, but that spread the wealth consistently over the area I “washed” and made it all appear brownish. I tried steel wool after several of these “rinsings” and although the surface brightened up somewhat, I am still left with a light metallic brown surface.
Without resort to insults, “you should’ve”s or “well, I’ve never done that before,” can anyone tell me first, how to ensure there is not going to be ongoing damage as a result of my error, and second, how best to restore the surface to the shiny, silvery, professional thing of beauty that it once was?
Thanks in advance for your advice and suggestions.
Mark B(arshfield) Anderson
p.s. In case anyone was wondering, I have indeed kept the top of the saw clear ever since that fateful day. I learn quickly. . . .
Replies
The brown is likely rust since muriatic acid is another name for hydrochloric acid it's undoubtely eaten off any coating the top had and left it vulnerable. I'd try a green scotchbrite and then naval jelly and go from there. Good luck!
Mark, just so you don't go to bed with no cyber-sympathy goin' your way, I'll say "I'm so sorrrrrry that happened to you!"
Now, I'm no chemist (and only a novice WWer), but I'd think that the acid is pretty much neutralized and/or washed away by now, so ongoing damage doesn't seem likely. I'll pass along how I rejuvenated a solid steel router table top that had that icky red-brown look to it. I used my random orbital sander with WD40 as a lubricant, 400 grit and above. I read in the forums of other people using a RO sander to finish off after de-rusting tablesaw tops, so it's something to think about.
Now I'll move aside so the experts can speak!
forestgirl -- you can take the girl out of the forest, but you can't take the forest out of the girl ;-)
I agree with Jamie. Just wet sand the bugger with light machine oil and 400 grit or above. Then wax it with a good furniture wax - use a thin coat and buff well. Wipe off the oil before you wax, of course.
All you should have to do is wax and buff from time to time. Don't waste your time with the Top Coat sprays and all that - they work but not any better than wax and a can of wax used only for these purposes will last the rest of your lifetime. And you can put the wax where you want it - not always so with sprays. I'm also not sure if breathing Boeshield is good for you. You could eat a beeswax and Carnauba formulation...
Keep it natural and simple
Reminds me of the time I was working with some muriatic acid and my cabinet scraper happened to be in the general area. Next day I noticed that the scraper had turned a dark dull gray and felt different. I was never able to turn a burr on it again. It was as if the acid had changed the molecular structure of the steel.
Dust some baking soda on it, then wipe it around and off with a wet sponge. Then, rinse with clean water and dry several times. Lastly, dry with a heat gun or hair drier and use TopKote or Boeshield or car wax on it. Accept the fact that it is now etched.
The baking soda neutralizes the long lived acid, the water rinses off the salts. Then, heat removes all the absorbed water and an applied coating protects the cast iron!
If anyone sets a soda or beer bottle on your cast iron, throw a hissy fit or worse!
I live in Florida where high humidity is unavoidable, an ongoing problem with woodshop metal surfaces. My experience once a surface is cleaned/polished (WD40 and an orbital sander/silicon carbide paper): Meguiar's #26 high-end carnauba car wax was easiest in application and provided a very slick (low friction) surface... but moisture within the wax - rust develop after a few weeks.
Boeshield's T3 (I think that was the name), provided only about the same rust protection - but required repeated application (weekly, according to the mfg.). Another downside: the resulting surface was somewhat sticky. It was also labor-intensive in application, demanded signficant buffing once applied.
In my Florida environment TopKote seems to give a longer lasting rust-delaying surface, plus a very slick low-friction surface. Note that I said rust "delaying," not "prevention." TopKote seems to be better than the other two coatings, but it is not a magic bullet. I use it on four machine surfaces and it seems to do a decent job.
The best tip/trick I've come up with to keep temperature-change condensation off the metal surfaces is to place a - cover - on all surfaces. I use an old white Tyvex car cover, cut up into appropriate sized pieces. The Tyvex plus the TopKote gives me a reasonably good combination of protection... good, but not perfect.
In this instance, the culprit is the cure. You can wash the staining off, (or most of it) with muriatic acid, full strength. Lots of paper towels, lots of ventilation. Neutralize with baking soda wash afterward.
GC
Let me suggest that shiny is a very low priority. The high priorities are smooth - because having to push hard is both dangerous and tiring - and flat - so the work doesn't rock as it goes through the blade. Once you've got it smooth and flat, what would you rather do with your time, cut wood or polish your saw? Go into any commercial woodworking shop and you'll find that the table saw is stained and blotchy, because their time is scarce and they don't want to waste any of it polishing the saw.
I will agree with the other posters that you want to make sure all the acid is gone, to avoid pitting, which is not smooth. But once you've rinsed and/or neutralized the acid, I say wax the table and forget it.
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