Rust Removal Chemicals (Evaporust)

[Ross365]

You said that you are working with a precision ground component, and so whatever you do needs care. Ideally, you need a solution which will remove rust but contains a corrosion inhibitor to stop corrosion of the metal and this too has been discussed previously on the forum. I cannot recall whether Evaporust in inhibited. Sergei is knowledgeable in this area. Citric appreciably attacks metal at higher concentrations and higher temperatures.

The problem with electrolysis (which surely does dissolve metal) is that you always get variation of the current distribution across the sample (unless both the sample and the counter electrode are both uniform flat plates exactly parallel to each other), so the extent to which a surface is reacted may be quite variable.

 

[timgunn1962]

You said that you are working with a precision ground component, and so whatever you do needs care. Ideally, you need a solution which will remove rust but contains a corrosion inhibitor to stop corrosion of the metal and this too has been discussed previously on the forum. I cannot recall whether Evaporust in inhibited. Sergei is knowledgeable in this area. Citric appreciably attacks metal at higher concentrations and higher temperatures.

The problem with electrolysis (which surely does dissolve metal) is that you always get variation of the current distribution across the sample (unless both the sample and the counter electrode are both uniform flat plates exactly parallel to each other), so the extent to which a surface is reacted may be quite variable.

Edges affect the current distribution too. Strictly, I think you'd need uniform flat plates of infinite area exactly parallel to each other.

 

[Kram]

Look for or request the material safety data sheet for each product. That should tell you exactly what chemical is the active ingredient and they may likely be the same.

I would be surprised if electrolysis removed metal.

Its the same process uses in, for example, copper plating, where you are actually laying down metal.

Now with steel, you are not laying down metal, but you can see that the electron flow is such that there really isn't anything trying to remove the metal from the cathode end.

My own feeling is that electrolysis removes rust by localized gasing as much as anything else, but, again, this isn't going to remove good material.


If you want to compare evaporust and the other one, pull the cossh sheets and see what is in them both.

Annode disolves (by oxidation) and cathode plates. It depends which way around the items are connected.

 

[julianf]

Look for or request the material safety data sheet for each product. That should tell you exactly what chemical is the active ingredient and they may likely be the same.


Annode disolves (by oxidation) and cathode plates. It depends which way around the items are connected.

Thats what i meant - that there would not be metal removed from the cathode (in this case, the "work")

 

[Kram]

I would have assumed the work peice is conndcted to the anode and that the rust chemically wants to react before the solid metal.
Atleast that is what I have done before.

It appears I am wroing and the "correct way " on the internet is to connect work to cathode. I suggest that will do bugger all.

 

[MattF]

It appears I am wroing and the "correct way " on the internet is to connect work to cathode. I suggest that will do bugger all.

You assume incorrectly then. It does work very well for rust removal.

 

[mightymig]

You said that you are working with a precision ground component, and so whatever you do needs care. Ideally, you need a solution which will remove rust but contains a corrosion inhibitor to stop corrosion of the metal and this too has been discussed previously on the forum. I cannot recall whether Evaporust in inhibited. Sergei is knowledgeable in this area. Citric appreciably attacks metal at higher concentrations and higher temperatures.

The problem with electrolysis (which surely does dissolve metal) is that you always get variation of the current distribution across the sample (unless both the sample and the counter electrode are both uniform flat plates exactly parallel to each other), so the extent to which a surface is reacted may be quite variable.

So I have tried to address the uniformity of current by taking some scrap steel 12mm rods, and I used my rod bender to create two U shapes and then mig welded them together at 90 degrees with the two U shapes crossed in the middle to create a 4 legged 'stool' sort of arrangement. That way there is coverage at 4 sides plus the undersides in even fashion. I have then put this into a bucket with a dirt guard you would use for washing your car so the work piece can sit on that without fear of touching the positive connection. Ill take a picture if that doesn't make sense but I am sure you can visualise it.

I am also going to put a car battery as the power source, with the battery charger trickling that. I heard that cheap battery chargers can have small issues of converting the AC to DC and therefore some of the rust can be deposited elsewhere back onto the workpiece, so the smooth DC of the battery apparently resolves that.

In regards to rust prevention, I will take the parts out of the electrolysis bucket, dry them off and blast them with compressed air and then spray them down with ACF-50 very quickly to prevent the flash rust.

Cheers

 

[mightymig]

For anyone ever coming back to this thread, ignore any commercial Evaporust or chelating solution. You can now just follow this guide on YouTube

and make your own for pennies compared, and a thorough test shows the DIY chelating solution works both longer and removes the same minimal amount of metal as Evaporust.

 

[fizzy]

For anyone ever coming back to this thread, ignore any commercial Evaporust or chelating solution. You can now just follow this guide on YouTube

and make your own for pennies compared, and a thorough test shows the DIY chelating solution works both longer and removes the same minimal amount of metal as Evaporust.

Brilliant thanks so much for posting.
Adding caustic such a sodium hydroxide or washing soda etc to citric acid makes it more neutral and actually makes it work better. A bit of fairy liquid as well.
Works much better than straight citric. Should stop things turning black.
Massive thumbs up for finding this

 

[iNf]

Brilliant thanks so much for posting.
Adding caustic such a sodium hydroxide or washing soda etc to citric acid makes it more neutral and actually makes it work better. A bit of fairy liquid as well.
Works much better than straight citric. Should stop things turning black.
Massive thumbs up for finding this

Already discussed here along with the recipe
https://www.mig-welding.co.uk/forum/threads/home-made-evaporust-formula.138522/
Can confirm it works well. Just make sure you put the bicarbonate in before the washing up liquid unless you really like bubbles