Hey fellahs! I'm removing rust from my 29 A frame and have noticed two distinct differences in the resulting "clean" metal based on the two methods I'm using. In the first method, I'm just using one of the Carbide sanding pads (like a hard sponge infused with sanding grit). Whether I'm getting rust off of the 80 year old frame or the SoCal crossmember welded to the frame, the steel always ends up being the normal grayish/silver color when clean. However, when I use a steel cup brush on my angle grinder, the crossmember looks the same as the use of the sponge, but on the 80 year old frame it looks like its taking off the old paint/rust but ends up looking blue or black and shiny...kinda like a bluing finish on a gun. Any ideas what is causing this and if it's detrimental to me applying Ospho, primer, or paint?
I'd venture that the cup brush isn't removing the iron oxide on the frame-it's only polshing it. Rust is pretty hard stuff and you need to either cut it with an abrasive or attack it chemically.
Well, if it's polishing it, then it's actually performing a "rust bluing" process that is actually a legitimate method used on firearms. The rust isn't thick, only surface rust mostly. So is a process occurring that is good/bad/neutral?
what happens when u hit it with a grinder? is it the method or the steel thats different? 80 years ago they used way better metal than nowadays.
if its turning blue or lite black your probably getting it awful hot, burning the metal.i use cup brushes all the time i can get the metal to look like a new silver dollar, but if i get in a hurry and push on the brush then i get the bluing and thats because it got hot.real hot.
see, I was thinking that, too....but I'm not really spending much time on the steel or pushing into it very much. That's what's weird. I'm only spending several seconds over an area, at that. I didn't sense any real heat coming off of it.
Id bet quite a bit that the steel is somehow different. Henry made some good stuff and the best welds I ever done was on 80 year old Henry steel.
well brother if your sure your not burning it the mr.dale and the fng are probably right .black oxide
how about the sand blasting method? to me that the closest youll ever get to actualy removing the rust, sanding and wire brushing dont do it for me, sanding can but it takes a huge amount of it. jeff
I'll snap off some pics of it and post in the next day or so. If it is indeed bluing/black oxide, what are the implications of applying primer (acid etch or otherwise) over the top?
Yeah...I'd love to have done that...but I'm kinda poor and not doing a show car build. That would run me at least $250 out here in Burbank, CA.
I would definitley say it is iron oxide. The exact same thing happens if you try and remove mill scale, which is iron oxide, off of cold rolled steel with either too fine a grit abrasive or too much speed it just polished up the mill scale and it looks blueish in color. Unfortunately I have no anwser on the safety of painting over it. I would guess if left shiney paint would not adhere very well.
poboyross, I know exactly what your talking about, doing the same on my 57 F100 now. I have found a very light grit flapper wheel will work where you have to weld, but I would NOT flapper disk anymore than that. I actually like the blue-ish color the wire wheel leaves. I think it may be a resultant of an oil based paint from the factory... but I am able to get it bare steel if you wire wheel a tad more. Im subframing mine, and was going to spray everything with clear paint to keep rust down and keep the blued finish on the whole frame.
Ouch, that ****s, itd cost me about $75 here to get blasted. ive heard it more expensive for blasting in CA. JEFF
I found the same thing with wire wheels, thats why I stopped using them, unless its to get scale or crust build up off. Now I use the 3M BLACK corral wheel on a drill, they bring the surface up like new and dont remove hardly any material. Flappers are too aggressive for my liking, great for taking welds down.
Why don't you check into the laws on sandlasting in Ca. It may not be ilegal to do it yourself v/s a comericial company. If the frame has no paint on it, maybe it is not a hazzardious waste. The sand can be obtained from a swiming pool place. A small syphon gun will work faster than sanding or wirebrushing.
The sandblasting is removing the rust, resulting in clean looking metal. The wire wheel will take off the loose stuff but is just polishing the rest of the oxidation, it is not getting it very clean. If the metal is just wheeled, sooner or later it will just rust again even if it is coated. Here is the process that I use: Sand blast the panel, sand with 80 to 180 grit on a DA, wax and grease remove, tack, spray bare metel with a metal etch primer, then coat it with an epoxy primer.
i have a cheapo $20 siphon blaster and a bag of black beauty in a 5 gal. bucket. i run tarps all around to contain some of the mess. if your compressor is big it'll make quick work of that frame.
So I went home and use the abrasive pad on the frame areas I had already made a p*** over with the cup brush. The black material came off with some elbow grease....acted like it was like gun bluing, too. It was a pretty tough coating that had been created. However, I discovered that there was still rust under it. I think that it did, indeed, create a rust-bluing scenario. It only converted the top layer of rust. SO...I guess I'll continue my search in the Burbank area for a reasonable price on media blasting. Surprisingly, most of them I found ONLY do buildings. How weird.
I used the 3M Scotch Brite disc's like these http://www.tooltopia.com/3m-automot...oglebase_18u&gclid=CL6-o9iUnq4CFWgZQgodXEZYKg on a variable speed drill to do a frame of mine some time ago and they worked beautifully. They are not cheap but we used them in a shop I was in to strip painted aircraft parts and the techs changed them after very little use so I grabbed the used ones. I don't recall how they worked on heavy rust. My frame was in pretty decent condition.Still might be a lot cheaper than sand blasting for you.
Not sure what you mean by "steel cup brush" but if you use the knotted wire wheel weldor's use to remove scale you will probably have better success. Lowe's sells a small wire wheel knotted brush that you can use in a die grinder or you can also use one of these http://store.cyberweld.com/wiwhandcupbr.html. The blue color is not actually "bluing" when speaking of making firearms. The blue color you are getting comes from the rusty layer on the metal getting hot enough to turn blue from the friction of the wire wheel.
Not sure what you mean by "steel cup brush" but if you use the knotted wire wheel weldor's use to remove scale you will probably have better success. Lowe's sells a small wire wheel knotted brush that you can use in a die grinder or you can also use one of these http://store.cyberweld.com/wiwhandcupbr.html. The bluing you are getting comes from the rust on the metal getting hot enough to turn blue from the friction of the wire wheel. Steel turns blue at about 572 degrees F. This is similiar to the coloring chart used when tempering steel. Look here. http://members.optushome.com.au/terrybrown/HeatTemperChartEtc.html
Quick question on topic. I was thinking of following this process for some motorcycle tins. Are the spry can versions of the acid etch acceptable. They even have the epoxy in a 2k can. I don't need a lot of product and they seem to state they will accept any top coat.
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