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Suckered by a scrap pile.


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My little metal working hobby has been pretty much dead since the world went bonkers and those of us who could continue to work did.  Then found themselves overworking. 

 

As somethings have slowly been coming back to normal, I made plans to make up new sets of tong held tooling.  I went to the local guy that I usually get my steel from and there was a pile of sheet metal on the floor that he offered to me.  As a decorative flower maker I saw a pile of rusty sheet metal as worth it. 

 

I got home and sorted out the sheets, all things painted - tossed to the side as not usable.  I then found a few clean sheets of the gauge I usually use for my roses.  I never had time to look at it too closely until today.  The sheets didn't look right for clean hot or even cold rolled steel, seemed a little too bright.  Also the parts with rust on them had a band of white at the edge of the corrosion.  At least my brain told me to test it somehow before I got plans together to cut it up and use it. I splashed some vinegar on it to see if it rusted to a known piece of cold rolled that I also splashed with vinegar.  Behold it did not rust the same, instead it turned white and cloudy, and indication of some kind of plating.  Moreover the vinegar clearly bubbled on these sheets.

 

I have a lot more of heavy gauge material from the haul that is clearly rusted to the point if there was a plating on it, its no longer there.  However I fell for a deal on unknown material due to the excitement of having some money to spend and getting a chance to make a dozen flowers or more out of this haul. Now my brain is kicking me saying I've wasted some of my hard earned cash on material that may be unsafe to use. 

 

lesson learned, never just jump into a deal if the person who has it - doesn't know what it is either.

secondly, as my workshop is so small and I only make about 5 items a year, don't trust the big box store for their welding steel section.  I used to get my sheet metal from the local big box store, but in recent years, I've noticed more things are zinc coated or not clearly marked as coated.

 

   

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you got galvanized steel cut your shapes out then soak in strong vinegar till the zincs all gone then its safe to heat and beat i do this when i need to weld pipe for a project and their out of what i need in black pipe

Brandon Sawisch bladesmith

 

eagles may soar but weasels don't get sucked in to jet engines

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Yes that is the best option that I have to get use out of what I got.  For right now, I'm kicking the sheets to the side to clean up and get the heavier gauge stuff ready for plasma cutting.  I have never stripped coating off of any pieces before.  Other than looking for black metal to reveal itself, any other things to watch out for to know the coating is totally removed? 

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When I use vinegar to remove galvanizing, I just soak it until it turns black.  For things like screws that have a very thin coat of zinc that takes maybe an hour.  For things like shiny sheet steel where you can see a bit of crystallization in the zinc, it takes overnight and sometimes a change of vinegar.  For hot-dip galvanizing, the thick, dull gray with big visible crystals, vinegar won't handle it. Use muriatic until it starts eating the underlying steel, or even better, just don't use hot-dipped as forge stock.

 

If it's tinplate, you may have to use muriatic to start with.  Zinc galvanizing on sheet always shows a bit of crystal pattern. Tin never does, it's just shiny. 

 

Bright-finish screws or all-thread aren't really galvanized, they're just tumbled in zinc dust.  

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It must be tin then, because the sheets have none of the crystal pattern on them. Just bright and white-ish where I tried to remove some of the plating. I've resolved to just keep that steel on the side I have enough from the haul to make a lot of stuff.  

 

Of the other thinner sheets I have, I cleaned off some of the rust to them, and noticed that they are blued. I don't think they are heat tinted as a wire wheel will not strip it off. I had to use a little bit of sanding to strip a section of that. I've thrown automotive springs in the fire before which may be chemical blued, however I think those are just tinted.  Is there any risk in heating chemical blued steels as well? Before I've just not known better to ask.  With the quantity I'm looking at doing, think its best to ask those who know better. 

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Good question on the chemical bluing. I don't know the answer, either.  Some cold bluing compounds are selenium based, and say they are toxic, but I have no idea how heat affects it.  

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2 hours ago, Daniel W said:

It must be tin then, because the sheets have none of the crystal pattern on them. Just bright and white-ish where I tried to remove some of the plating. I've resolved to just keep that steel on the side I have enough from the haul to make a lot of stuff.  

I would just add that hot dip galvanized/galvannealed sheet doesn't always have super visible crystals. I have recently been handling a lot of coated sheet steels and most of them have a matt bright grey color as received. In a hot dipped Zn coating there is also some amount of alloying with the base material, which forms a gradient of different Fe/Zn/Al compounds which are harder than the pure Zn outer layer and may have a different susceptibility to pickling as well. In a galvannealed coating, these intermetallics make up much more of the coating since there has been more time at temperature to diffuse in Fe from the surface.

 

I realize most of that probably isn't too useful, but this is a topic that has been on my mind lately. I have found that coated sheet makes an excellent material for precision templates for scribing profiles. In thin gauge (not sure off the top of my head, but I prefer it thin enough to cut with tin snips) it's easy to cut and shape and then it has excellent rust protection (which I have found important with all of the water involved in grinding) at a fraction of the cost of stainless sheet.

Edited by Aiden CC
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