The authoritative public forum
  for Metal Finishing since 1989
  

  -----

Rusty problem

Cast iron components after subjecting to high temperature oxidation to remove minute burs(TEM deburring process)and further acid cleaning of oxidised surface will not ensure free from rust. After acid cleaning proper neutralisation , drying and rust preventive oil application is taken care. The rust will appear after some days due to oozing of entrapped acid in the porous and also from uncleaned rust.
Is there any alternate cleaning process available or any further protection like cold blackening is possible after cleaning.

Nagendra J K
Electroplating - India
2007

---

2007

Dear Mr.Nagendra,

Just a thought, why can't you go for a mild alkaline water rinsing after acid cleaning, so that the acid that oozes out be neutralized.

Yes..the cold blackening should be possible for Cast Iron components. But the feasibility is depending upon the factors like, shape of the components, cost etc..

regards,

Keshava Prasad M
- Chennai, India

---

Thanks for the response.
Yes. we are neutralising with alkaline water rinse but still frequent rust problem persists.
Some body suggested, surface blasting by aluminum oxide by high pressure to remove rust and followed by oxidation phosphating.
what exactly the oxidation phosphating process and what is the level of corrosion protection.
Some details on cold blackening.

Nagendra J K
- Bangalore, India
2007

Ed. note: we have a brief FAQ about black oxide vs. cold blackening. For greater depth, see the Metal Finishing Guidebook. Most cold blackening is proprietary, and you can get technical data sheets from the vendors.

---

Try Hot and cold cycles of water rinse as the last steps. It should definitely help to extract any trapped acid. Good luck..

Hemant Kumar
- Florida, USA
2007