Letter 22038

Internal rust removal [Maryland] 

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We recently purchased a used hot press which is basically a large furnace with a 250 ton press going through it that we use this to heat and press powders for high strength lenses. The furnace has cooling jackets all through it and since it has sat for a while it has collected a lot of rust internally. I'm looking for something that I can circulate through the system to remove the rust. I'm really looking for something environmentally safe as well as safe for my employees. Any help is greatly appreciated.

Mark Heinekamp
composites - Millersville, Maryland, USA

I haven't expiremented with it much myself, but if I recall Citric acid is a very good rust remover and phosphoric acid will remove the rust and protect against future rust. This is outside my area though... read letters 14042 and 16801 for better tips.

Good Luck.

Jim Gorsich Accurate Anodizing Inc. Compton, CA, USA

Citric Acid is a very good rust remover that will not harm most metals, but if you add Citric Acid to a pH of around 2.0 and then Add Ammonia and bring the pH back up to around 4.0-5.0 this will clean the system much faster. Also if you can heat it then it will clean faster. Several of the Water Treatment Companies also have neutral cleaners that will do the job, but this is not cheap. The other possibility is using an acid cleaning company, but again not cheap. With the citric acid, as the rust is removed the pH will climb back to around 6.5 and can be disposed of easily.

Good Luck,

Chip Harper
- Hartsville, SC

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