How To Rust Magnetic Iron PLA Filament

comparison between treated filaments.
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How To Rust Magnetic Iron PLA Filament
5 (100%) 4 votes

How To Rust Magnetic Iron PLA Filament

Proto Pasta  has approached 3D-PT to review their exotic PLA filaments blends. I have reviewed their Aromatic Coffee and Conducting PLA in a previous blog. I developed a rating system for filaments with their Stainless Steel PLA, and in a future blog I’ll review how to polish it to a nice shine.
For this Magnetic Iron PLA, I wanted to make a trivet for a family member. As a challenge, I did not want to rust the whole thing, just the inside parts that would be hard to get to. This way It would look more like a hard-worn and aged rustic object, not just something that was rusted yesterday.


After watching the company tutorial on how to rust their prints, had an idea of what to do.


How To Rust your Print

  1. Use a wire brush or sandpaper to expose more of the iron filings in the print. For this I used a fine sanding pad and emery board to rough up the areas I want to rust, leaving the other areas alone.
Sanding a leaf

Sanding the areas you want to rust.

  1. After watching this video, I found that prints rust best when they are wrapped in a solution of salt water and kept in a bag overnight.

I used a paint brush to apply the mixture to the areas to rust. Because I want to limit the rust, I used bits of paper towels soaked in a saline solution placed over the desired areas.


3. I put the treated print in a closable container overnight and see what happens. If you can find a warm area to put this, that will make the rust happen faster.

Rusting spots I want

Using bits of paper towels to rust selected areas of the print.


Results, Day 1

After 12 hours in a container I started seeing some rusting. In an effort to speed it up, I put it on the warm bed of my printer, and I noticed that doing that helped. The PLA surrounding the iron does slow the process, so heating your print or solution will help.
Some of the spots I wanted to rust had not caught up to the others. I re-sanded those spots to try again.
The next time I applied the factory recommended mixture of vinegar, hydrogen peroxide and salt.


Results, Day 2

The factory solution of white vinegar, hydrogen peroxide and salt worked so much better !

Mix 1 part hydrogen peroxide with 1 part white vinegar, and add just enough salt to saturate the solution (till you can’t mix any more salt into your liquid).
I repainted the solution onto the spots to rust, and left it in a container overnight. I then opened the container and let the print dry out.

comparison between treated filaments.

Un-rusted (left) and rusted (right) trivets.

The final result was a earth-toned mix of oranges, reds, browns,  and charcoal grays where I applied the rusting solution. There was some rusty salt crust on the print as well, which did flake off at times. The rust appears on the surface, and may brush off with a wire brush.

Rusy spots

Close up of rust-treated areas.


Final Thoughts

Proto Pasta’s Magnetic PLA is a filament for advanced 3D printers that want to play with the finishing qualities of their filament. The rusting treatment does take some practice to get down, but you can work with it to produce rustic looking prints.

I may have been a bit ambitious trying to rust specific spots of this print, but I’m still pleased with the result.
As for its magnetic properties, the sample did stick to a magnet but weakly. According to the company’s site

It attracts magnets (neodymium type recommended for strongest attraction).

Induction at magnetic saturation about 0.15 Tesla.

Permeability between 5 and 8 independent of frequency up to 1 MHz.

It is magnetic, but you will be hard pressed to make anything like a DC motor out of this.
In a previous blog I developed a rating system for filament. Under this scale it rated the following.
1. Flexibility: Like the Stainless Steel PLA, the high iron content caused the filament to snap at 70 degrees. 4.3 pts
2. Color: Printed has more of a shine in it, but color stayed the same. 3 pts
3. Starting Quality: Started well. 2 pts
4. Warping: No warping. 3 pts
5. End of Print: Came clean off build plate. 3 pts
6. Environmental: No smell, but iron fillings and dust may be a concern. 1.5 pts
7. Special consideration: Being an abrasive filament (it feels like emery board), this will require a hardened nozzle for extended prints. It did chew into the idler arm on my print head. 0 pts
8. Processing / finishing the print: This can be polished with a grinding wheel, or treated with household chemicals to have a rusted appearance. 2 pts
FINAL SCORE: 18.8 / 28

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