BlueWolfFab
Running Behind
- Location
- Eagle Mountain
Sooo with some mention of people using muriatic acid (37% Hydrochloric acid) to remove zinc or other coatings off of parts, and also in the name of experimenting, I'm going to use some muriatic acid to remove the mill scale from some steel in order to make building my winch bumper an easier and better process. I don't really recall seeing any threads on here that go into detail about it so I'll share what I do.
From some research, the mill scale on mild steel is just part of the manufacturing process, when the steel is hotrolled into a plate, the mill scale forms on the exterior surfaces of the steel as the steel cools down from the processes of working the plate, and eventually forms a layer of hard material (harder than the center of the steel). Because of the surface of the mill scale it naturally helps delay rusting of the steel, but it also makes paint, powdercoat and other coatings less likely to adhere properly, and also can effect your welds a little (most noticeable in TIG welding) so for a few reasons I'm choosing to work with steel with no mill scale.
A few options;
• I could have removed the mill scale mechanically, with abrasives, (grinder disc/flap wheel/DA sander etc) but I've done that before on small parts and it's a PITA, noisy, time consuming and can leave a sub-par finish if you happen to get grinder marks too deep etc. Could also just have the parts sandblasted but that's just an extra step too, especially where most people have to take the parts to a sandblasting company to have their parts blasted.
•I could have bought HRPO (Hot Rolled, Pickled and Oiled) plate, which essentially is basically buying an entire sheet that has already been bathed in muriatic acid at the steel plant to remove the mill scale, and then coated with a film of an oil to help prevent flash-rusting. Further down the road when I finally get a plasma cutter again for my plasma table, I'll likely go this route to avoid the hassle of dealing with mill scale at all, but HRPO comes at a higher initial cost and not all steel suppliers always carry it.
•Option 3, I try messing around with DIY muriatic acid for stripping the mill scale and see how it goes.
_____________
Bought 2 gallons ($7.50 each) at a swimming pool supply store in Sandy, and from watching Breaking Bad I know that hydrochloric acid doesn't eat Polyethylene plastic
so I also bought a Rubbermaid polyethylene storage tote at Home Depot ($17)
I didn't want to get too large of a storage tote so that my 2 gallons of acid would actually fill up the bottom of the tote enough to cover the steel completely. I had an 18"x24"x.25" steel plate I was planning on using for my frame-tie ins, but struggled with finding any tote that could completely fit the steel in the bottom. I could have bought a polyethylene rectangular box from a few places that were specifically made with this kind of thing in mind (flat bottom, thick material, 90° corners and walls etc) but most of what I could find was around $100 anyways so I will give the storage tote a shot and see how it goes first.
Found a tote that was about 26"x15" in the bottom, so I cut my steel plate to 14" of width off the one side so that left me with a piece that's 24"x14" and that will still give me enough room to make both of my frame tie-in plates.
Dropped it in and poured in the first gallon of muriatic acid and found that I didn't need the 2nd gallon in order to cover the whole plate, so I only poured in the one gallon.
You can see some of the fumes that instantly started coming off the acid, I'm wearing neoprene gloves and a painting respirator but still held my breath and tried to keep out of the fumes as much as possible as the fumes can do some burns to your lungs and eyes and stuff.
P.s. I'm doing this on my back deck as I don't want to deal with the fumes etching all my tools and stuff in my garage. I'll let you know if doing it on my deck was a mistake lol.
I couldn't find any info on how the acid performs in cold temperatures, other than its freezing point was like -50° C or something so I didn't have to worry about that. Current temps here are 29° F. I'll see if that effects what needs done. From my research I've found I should need to let it bath for about two hours in order to remove the scale, but I'll see how much the size of my plate and or temps effect that.
When it's done I'll neutralize the acid with a baking soda solution.
It's currently been in for about 45 minutes and I'll flip it over here soon, I welcome any tips or comments.
From some research, the mill scale on mild steel is just part of the manufacturing process, when the steel is hotrolled into a plate, the mill scale forms on the exterior surfaces of the steel as the steel cools down from the processes of working the plate, and eventually forms a layer of hard material (harder than the center of the steel). Because of the surface of the mill scale it naturally helps delay rusting of the steel, but it also makes paint, powdercoat and other coatings less likely to adhere properly, and also can effect your welds a little (most noticeable in TIG welding) so for a few reasons I'm choosing to work with steel with no mill scale.
A few options;
• I could have removed the mill scale mechanically, with abrasives, (grinder disc/flap wheel/DA sander etc) but I've done that before on small parts and it's a PITA, noisy, time consuming and can leave a sub-par finish if you happen to get grinder marks too deep etc. Could also just have the parts sandblasted but that's just an extra step too, especially where most people have to take the parts to a sandblasting company to have their parts blasted.
•I could have bought HRPO (Hot Rolled, Pickled and Oiled) plate, which essentially is basically buying an entire sheet that has already been bathed in muriatic acid at the steel plant to remove the mill scale, and then coated with a film of an oil to help prevent flash-rusting. Further down the road when I finally get a plasma cutter again for my plasma table, I'll likely go this route to avoid the hassle of dealing with mill scale at all, but HRPO comes at a higher initial cost and not all steel suppliers always carry it.
•Option 3, I try messing around with DIY muriatic acid for stripping the mill scale and see how it goes.
_____________
Bought 2 gallons ($7.50 each) at a swimming pool supply store in Sandy, and from watching Breaking Bad I know that hydrochloric acid doesn't eat Polyethylene plastic
so I also bought a Rubbermaid polyethylene storage tote at Home Depot ($17)I didn't want to get too large of a storage tote so that my 2 gallons of acid would actually fill up the bottom of the tote enough to cover the steel completely. I had an 18"x24"x.25" steel plate I was planning on using for my frame-tie ins, but struggled with finding any tote that could completely fit the steel in the bottom. I could have bought a polyethylene rectangular box from a few places that were specifically made with this kind of thing in mind (flat bottom, thick material, 90° corners and walls etc) but most of what I could find was around $100 anyways so I will give the storage tote a shot and see how it goes first.
Found a tote that was about 26"x15" in the bottom, so I cut my steel plate to 14" of width off the one side so that left me with a piece that's 24"x14" and that will still give me enough room to make both of my frame tie-in plates.
Dropped it in and poured in the first gallon of muriatic acid and found that I didn't need the 2nd gallon in order to cover the whole plate, so I only poured in the one gallon.
You can see some of the fumes that instantly started coming off the acid, I'm wearing neoprene gloves and a painting respirator but still held my breath and tried to keep out of the fumes as much as possible as the fumes can do some burns to your lungs and eyes and stuff.
P.s. I'm doing this on my back deck as I don't want to deal with the fumes etching all my tools and stuff in my garage. I'll let you know if doing it on my deck was a mistake lol.
I couldn't find any info on how the acid performs in cold temperatures, other than its freezing point was like -50° C or something so I didn't have to worry about that. Current temps here are 29° F. I'll see if that effects what needs done. From my research I've found I should need to let it bath for about two hours in order to remove the scale, but I'll see how much the size of my plate and or temps effect that.
When it's done I'll neutralize the acid with a baking soda solution.
It's currently been in for about 45 minutes and I'll flip it over here soon, I welcome any tips or comments.
