Question re electrochemical marking of stainless steel

[HCB]

TL;DR

Which voltage range (I believe in AC) is necessary and which chemicals are preferred as the electrolyte(s)?

First: this post is regarding the marking of stainless steel with an electrochemical process which involves one or more electrolytes in solution. I felt this area of the site sounded like an appropriate place to post this as it involves both materials and chemistry. My apologies if this isn't the right place.

Hello, All. I've been having fun as a semi-retired guy messing with various electrochemical processes, namely: anodizing aluminum and titanium, and rust removal on mild steel and other alloys which develop red iron oxide. I have a new shop building and I would really like to mark outlets with circuit information, mostly which circuit the outlet is connected to. Having the faceplate marked is my goal. I tried this almost 2 years ago when the first shop was put up (I set it on fire in May, a little over a year after it was built...not a good thing). What I tried then was masking the faceplate with painters' tape and having it turned into a stencil by a guy with a laser cabinet. The laser was far too weak to etch the galvanized coating but I wasn't worried, I thought I'd eat the galvanizing off with muriatic acid with the tape as the stencil. Wrong. Maybe it had a coating on it which the laser didn't remove. Regardless, it didn't work well for some reason and, maybe due to the acid, the painters' tape was a beast to remove. I abandoned the marking then. I could have him use some special spray-on product and then laser the design (almost like spray-on laser printer toner...sort of) for this go-around but I'd really like to do as much of the process as I can myself.

I have found commercial units which claim to mark, not etch, stainless steel through an electrochemical process. Cougartron, Etchdrop, Tigbrush are a few of the manufacturers. Not only am I not doing this for profit, I don't want to purchase a tool to do one job. Plus, I'm a DIY type and I feel this should be completely doable. I've not found much DIY information on this subject, however. There are plenty of videos and sources for information on *etching* various steels (very common in knife-making circles), but not a) *marking* and b) on stainless (well, not that I've found). All the machines I've seen online as well as the DIY etching use an absorbent material connected to one wire from a power supply, an electrolytic solution absorbed into said medium, and the other wire from the power supply connected to the workpiece; this is, that I've seen, not a bath process. The "wand" is dragged across the work piece while current is conducted across the electrolytic solution in the medium. In the videos I've watched about such commercial units, the marking takes a matter of seconds (less than 30), and appears to be a pretty dark black color. They claim it's very durable. Yes...marketing, but I'm hoping there's some truth there. The marketing materials I've read indicate that this process should be good for 300 and 400 series stainless steel.

Reading MSDS/SDS for the electrolyte solutions offered from some of the companies doesn't reveal much about their composition. The best I found was one with: NaCl, cobalt chloride, citric acid, and I believe it was calcium chloride. There are many electrolytes which can be used in the various "electrolysis" processes and, usually, seem more suited to one process than another (sulfuric acid for anodizing Al, trisodium phosphate for anodizing titanium, etc).

The general rule seems to be that, for marking instead of etching, AC is used. As I can get stainless steel outlet faceplates, I got a couple of pieces of stainless steel and did some tests today with various electrolytes and a 12vac wall wart. I tried a few combinations of citric acid, calcium chloride, NaCl, potassium chloride. Nothing worked very well. The best I got almost looked black when still wet but looked more like light brownish charcoal when it dried. I futzed around with different combinations but NaCl and citric acid gave me the best results of my poor attempts. After it was dry, it was not very durable and was easy to rub off partially with just a dry paper towel.

All that to get here: I would like to know about how stainless steel is marked with an electrochemical process, which voltage or range of voltages is appropriate, AC or DC (although I *think* it's going to be AC, if I knew so much, I wouldn't be here asking questions), which electrolytes are better suited to the process, what is the "black" color (which material like iron or magnetite, etc), and if there are stainless steel alloys which would be less well-suited for this process. If you can help with any of this information, I would appreciate it.

Thank you very much for your time.

(The copy of War and Peace above is due to many years of reading forums where people ask complex questions in one paragraph, if that, with no context.)

--HC

 

[Tom.G]

A couple alternatives:

1) Try this, although it takes a little practice. A low voltage power source with a fair current capability - even jumper cables from your car battery will work but is overkill, you probably don't need more than 30 Amps though. (hint: keep the engine running)

A) Get the Carbon rod from a Carbon-Zinc flashlight battery. You can file a blunt point on it, or just use the corner at the end of the rod
B) Connect one lead of your power source to the workpiece and the other lead to the Carbon rod from the flashlight battery.
C) Gently drag the Carbon rod across the workpiece to etch the surface as needed.
​

2) Draw a map of the workshop, marking where each outlet is. (and lights)

A) Plug a lamp into each outlet (limited by number of lamps available)
B) Start flipping breakers and note the breaker No. on the map at the affected outlet.
C) Tape the map to the inside of the breaker box door... or to the wall next to the breakers.​

The map approach seems more practicle because you need the information at the breaker box, not at the dead outlet.

Cheers,
Tom

 

[HCB]

Tom, thank you for your reply.

What you're describing with the carbon rod sounds like it will effectively make a little lightning storm across the surface of the metal: very small, short arcs. That might work but I would seem similar, minus the air-gap arcing, to using an electrolyte in solution. In other processes using DC, polarity makes a difference. In anodizing aluminum and titanium where the goal is to increase the oxide layer, the workpiece is connected to the positive terminal of the DC power supply. In removing rust (red iron oxide) from steel pieces, the negative terminal is connected to the workpiece. With air-gap arcing, the polarity may be moot as the marking may be done by the actual arcing, not the less-violent flow of electricity through an electrolytic solution. I may try that to see what happens.

As for carbon rods: there is a process called "gouging" or "air-arc gouging" in metalworking. Readily available are carbon rods, usually with a layer of copper as a jacket. The jacket is reasonably easy to slice and peel, leaving a carbon rod behind. I use these sometimes as the sacrificial anode in electrolytic rust removal. Easier and less messy than obtaining from some of the batteries as I've seen done.

The goal isn't to find which circuit a particular outlet is on, it's to be able to identify which circuit I'm connecting to when I plug something in. While I run many circuits at the floor/workspace level and alternate the outlets carried on them, I still like to know that this device isn't plugged into the same circuit as that device. Also, on the occasion that I trip a breaker (usually with a high initial load device near the breaker rating: think chop saw), it is super handy to look at the outlet and know which circuit I just tripped so when I get to the breaker box I know I'm looking for "Circuit X". I use the Square D QO series breakers which have a visual indicator that they're tripped; so even getting to the box and knowing which circuit I'm looking for isn't necessary. Finding any other brand of tripped breaker isn't a real big problem. I would just like to have this level of clarity in my wiring, specifically the outlets.

I could use a Brother lableler, write on them with a Sharpie (which is how I've done it before), paint the outlet covers different colors, or any of a number of different things to know which outlet is on which circuit. I want to electrochemically mark the stainless steel faceplates. I want to be able to mark the SS, I want the crisp, neat labeling, and I'll gain a new ability in the process.

--HC

 

[berkeman]

I tried this almost 2 years ago when the first shop was put up (I set it on fire in May, a little over a year after it was built...not a good thing).

Just curious, how did you manage to set your shop on fire? Maybe there is a safety lesson in there that you can pass on to us.

 

[HCB]

Just curious, how did you manage to set your shop on fire? Maybe there is a safety lesson in there that you can pass on to us.

I did what I've done thousands of times over 23 years. I checked myself as I have in the past. I missed a detail. Something was flammable and within reach. I'm still not entirely sure what it was. But over $100k of not-insured contents and my favorite cat died. Things happened quickly. Praise the Lord I made it out.

I didn't know the contents had to be separately insured. Oops.

--HC

 

[HCB]

TL;DR Summary: Which voltage range (I believe in AC) is necessary and which chemicals are preferred as the electrolyte(s)?

First: this post is regarding the marking of stainless steel with an electrochemical process which involves one or more electrolytes in solution. I felt this area of the site sounded like an appropriate place to post this as it involves both materials and chemistry. My apologies if this isn't the right place.

Hello, All. I've been having fun as a semi-retired guy messing with various electrochemical processes, namely: anodizing aluminum and titanium, and rust removal on mild steel and other alloys which develop red iron oxide. I have a new shop building and I would really like to mark outlets with circuit information, mostly which circuit the outlet is connected to. Having the faceplate marked is my goal. I tried this almost 2 years ago when the first shop was put up (I set it on fire in May, a little over a year after it was built...not a good thing). What I tried then was masking the faceplate with painters' tape and having it turned into a stencil by a guy with a laser cabinet. The laser was far too weak to etch the galvanized coating but I wasn't worried, I thought I'd eat the galvanizing off with muriatic acid with the tape as the stencil. Wrong. Maybe it had a coating on it which the laser didn't remove. Regardless, it didn't work well for some reason and, maybe due to the acid, the painters' tape was a beast to remove. I abandoned the marking then. I could have him use some special spray-on product and then laser the design (almost like spray-on laser printer toner...sort of) for this go-around but I'd really like to do as much of the process as I can myself.

I have found commercial units which claim to mark, not etch, stainless steel through an electrochemical process. Cougartron, Etchdrop, Tigbrush are a few of the manufacturers. Not only am I not doing this for profit, I don't want to purchase a tool to do one job. Plus, I'm a DIY type and I feel this should be completely doable. I've not found much DIY information on this subject, however. There are plenty of videos and sources for information on *etching* various steels (very common in knife-making circles), but not a) *marking* and b) on stainless (well, not that I've found). All the machines I've seen online as well as the DIY etching use an absorbent material connected to one wire from a power supply, an electrolytic solution absorbed into said medium, and the other wire from the power supply connected to the workpiece; this is, that I've seen, not a bath process. The "wand" is dragged across the work piece while current is conducted across the electrolytic solution in the medium. In the videos I've watched about such commercial units, the marking takes a matter of seconds (less than 30), and appears to be a pretty dark black color. They claim it's very durable. Yes...marketing, but I'm hoping there's some truth there. The marketing materials I've read indicate that this process should be good for 300 and 400 series stainless steel.

Reading MSDS/SDS for the electrolyte solutions offered from some of the companies doesn't reveal much about their composition. The best I found was one with: NaCl, cobalt chloride, citric acid, and I believe it was calcium chloride. There are many electrolytes which can be used in the various "electrolysis" processes and, usually, seem more suited to one process than another (sulfuric acid for anodizing Al, trisodium phosphate for anodizing titanium, etc).

The general rule seems to be that, for marking instead of etching, AC is used. As I can get stainless steel outlet faceplates, I got a couple of pieces of stainless steel and did some tests today with various electrolytes and a 12vac wall wart. I tried a few combinations of citric acid, calcium chloride, NaCl, potassium chloride. Nothing worked very well. The best I got almost looked black when still wet but looked more like light brownish charcoal when it dried. I futzed around with different combinations but NaCl and citric acid gave me the best results of my poor attempts. After it was dry, it was not very durable and was easy to rub off partially with just a dry paper towel.

All that to get here: I would like to know about how stainless steel is marked with an electrochemical process, which voltage or range of voltages is appropriate, AC or DC (although I *think* it's going to be AC, if I knew so much, I wouldn't be here asking questions), which electrolytes are better suited to the process, what is the "black" color (which material like iron or magnetite, etc), and if there are stainless steel alloys which would be less well-suited for this process. If you can help with any of this information, I would appreciate it.

Thank you very much for your time.

(The copy of War and Peace above is due to many years of reading forums where people ask complex questions in one paragraph, if that, with no context.)

--HC

I've continued to experiment. DC etching (actually removing metal) has been a little successful. Mixing 30% vinegar, NaCl, and citric acid, running around 30Vdc open-circuit, pushing about 0.7A, I have been able to quickly tarnish and then etch into a SS test outlet faceplate. Naturally, SS is supposed to be durable in harsh conditions and I'm trying to create a harsh condition it cannot withstand.

Discoloration using AC and a variety of electrolytes has been disappointing.

Here is a list of ingredients from one MSDS for one electrolyte for marking stainless steel. With insufficient chemistry knowledge, I can't know why this solution would work well (if it does) and my solutions don't work well.

CALCIUM CHLORIDE, SODIUM CHLORIDE, CITRIC ACID, COBALT NITRATE, POTASSIUM THIOCYANATE, COBALT CHLORIDE

All are listed as 1-5%.

Does anyone have any chemistry/metallurgy knowledge as to why this might leave a darker mark on stainless steel than other electrolyte solutions in the same process? I have the first three ingredients. I do not have and have not investigated finding the cobalt or potassium ingredients. Before doing that I would a) try the commercial solution to see if it gave a satisfactory result and b) like to know *why* it does what it does and if there are any other possible solutions.

Thank you.

--HC

 

[synch]

At a guess the cobalt is replacing metals in the stainless steel and the darker shade is from different texture or oxides. There is a similar technique where a weld is made less conspicuous by using a DC electrolysis and a brush,
IIRC the heat of welding selectively vaporizes chromium(?) which is replaces by the electrolysis. Maybe the AC electrolysis is selectively removing chromium (?).
Actually a bit of copper sulphate solution will act as ink on stainless, ( names have been changed here to protect the innocent - well clumsy and not so innocent maybe :) ) It is a black stain, might need a varnish layer of some sort.