[Link]

Dear all,

I have a small rack, iron (I think), its oxidized and rusty.
I wanted to know what the most easy way is to clean it, remove most of the dirt (left over paint) and remove the lose bits or rust.
The goal is to paint it again and I wondered whether there might be an easy way to do this rather than to try and sanding it (almost impossible).

I found white vinegar as a solution?
And baking soda? but perhaps there are other easy ways?

[curiouscat]

Sandblasting? Shotblasting? High Pressure Water Jet?

[Arkcon]

I've thoroughly cleaned and painted the wrought iron railing at my mothers house, and I'll give you some tips that worked well for me.  Some of my tips even have chemistry behind them.

Remove all old paint, rust and scale manually first.  Its just too much work for the paint or cleaners to do most of the work for you on stuff that's held loosely.  Once they're off, they take the cleaner with them, and so the next bit never sees the next bit of rust or scale.   So what I'm telling you to do is work first.  Seems like I have to tell every new poster on these boards that.  Heh.  Get a wire brush attachment for your drill, or get a Dremel tool for tight spots.

Once most of the rust and scale is off, if there's any paint, you might try a paint stripper.  Skip this step if there's no paint, but don't skip it if there is, you want a clean surface to start.  Note, some of the safer strippers are aqueous acid based, which means, yeah, by the time you're done, your iron will be rustier again, and you'll want to give it a quick, cursory, manual descaling again.  Sorry.

Go to the hardware store and pickup some naval jelly.  This is phosphoric acid in a gel matrix, you can slobber it on, and let it work on the scale and rust.  It's too weak of an acid to hurt bare iron, but if there's lots of scale (loose flaky rust) the surface will remain pitted afterward.  Hey, you wanted the rust gone right?  If part of it is mostly rust, you're gonna leave a hole.  Phosphoric acid really removes iron rust well.

Rinse it off with a dilution of sodium triphosphate, also from the hardware store.  This step is optional, but I really like it.  This is neutralized phosphoric acid, and you want the acid gone because acid speeds rusting.  Phosphate reacts with iron to form iron phosphate which doesn't rust, and it bind tightly to iron preventing further rusting. The best iron phosphate coatings happen in a highly basic medium, often electrolytically.  But still, you'll be making some with the naval jelly and STP.  Iron phosphate is a "thirstier" surface than bare metal for paint.

Apply one or two primer coats.  I like spray paint, but you can brush on two thin coats.  I like to use a certain brand, but any bare metal primer is good.  Try to buy the same brand of primer as paint.  Primer has superior coating properties.  But it tends to lack good pigmentation, seems to come in grey or white or brown.  The surface is even "thirstier" for paint, but will really lack wear capabilities.  So you can't stop here.

Apply one or two top coats.  The same rust resistant brand of paint, in the color and finish you want.  This will protect the primer from wearing off, and the iron from rusting more.

My father would just slap on more paint over the rusting bubbles every few years.  My through job has lasted 7 years outside with minimal touch up needed.

[Arkcon]

Sandblasting? Shotblasting? High Pressure Water Jet?

Very good ideas as well.  Not only will these help remove scale, they'll break off the walls of any pits you fhave for a smoother surface.  They'll also leave micro scratches for a thriftier surface.

Maybe someone will be by soon with a plan for electropolishing, if your rack is small enough.

[Link]

Just to be clear: the rack is a small rack used in labs to put tubes in!
It really is small!
The reason I want to clean it, is to see if it works out... if it does, I can fix the other racks too!
THe racks I am talking about are hard to find in shop these days, they have a particular size and are very usefull.

Sandblasting? Shotblasting? High Pressure Water Jet?

Perhaps I have been not clear enough: the rack is pretty small.. its just a rack that you use in a lab to put tubes in!
Haha sorry for the misunderstanding.

I've thoroughly cleaned and painted the wrought iron railing at my mothers house, and I'll give you some tips that worked well for me.  Some of my tips even have chemistry behind them.

{remove monster quote}

My father would just slap on more paint over the rusting bubbles every few years.  My through job has lasted 7 years outside with minimal touch up needed.

This is valuable information!
I'll keep it in mind, but for my job its a bit over the top :p

Sandblasting? Shotblasting? High Pressure Water Jet?

Very good ideas as well.  Not only will these help remove scale, they'll break off the walls of any pits you fhave for a smoother surface.  They'll also leave micro scratches for a thriftier surface.

Maybe someone will be by soon with a plan for electropolishing, if your rack is small enough.

I was thinking of, perhaps, putting the rack in a sonication bath! Would this not be a solution?
Altough, it might be bad for the sonication bath ?

[Arkcon]

If it will fit in the sonicator, you may get the rust off.  But you will likely still have to polish the metal with steel wool or something.  If this is a small lab rack, just wipe it with diluted phosphoric acid until you don't see any more rust coming off.  Then rinse well.  I doubt you'll want to paint a laboratory drying rack.  Also, if this is chrome plated steel, you're kinda spinning your wheels here, the more it rusts the more plating it will take with it, so the more it will rust and take more plating .

[Link]

If it will fit in the sonicator, you may get the rust off.  But you will likely still have to polish the metal with steel wool or something.  If this is a small lab rack, just wipe it with diluted phosphoric acid until you don't see any more rust coming off.  Then rinse well.  I doubt you'll want to paint a laboratory drying rack.  Also, if this is chrome plated steel, you're kinda spinning your wheels here, the more it rusts the more plating it will take with it, so the more it will rust and take more plating .

I am not sure what you mean with this?
The more plating it will take? You mean it will also "remove" the rack itself (not sure how to put it..)

Its a rack used to put glass tubes in (the tubes you use to grow a pre-culture, for example).

[Arkcon]

If its shiny, its not iron, its steel.  If most of it is as shiny as a bathroom faucet, then its likely medium steel, plated with chromium metal.  If its rusty, you've flaked off some plating and its only going to rust more.

[Link]

If its shiny, its not iron, its steel.  If most of it is as shiny as a bathroom faucet, then its likely medium steel, plated with chromium metal.  If its rusty, you've flaked off some plating and its only going to rust more.

Its not shiny...
So you would advise not to try to clean it?
It used to be painted with white paint.

[Arkcon]

Oh, then its likely mild steel or possibly iron.  Clean and paint as I suggested.  Or whatever facsimile you think will work for you.