Corrosion in Formic Acid (HCOOH)

Formic acid has proven to be highly corrosive at concentrations over 50% especially if contaminated by acidic oxidizing chlorides. Because of its corrosive nature at high concentrations material selection can be a challenge.
 

Stainless Steel, Nickel base alloys and Zirconium's Corrosion in Formic Acid

Formic acid is corrosive to many alloys including Stainless steel, Nicel alloys and Zirconium. Formic acid as a reducing agent and attacks stainless steels unless an oxidizing agent is added. Nickel base alloys perform better than SS 316, but are attacked if an oxidizing agent is present. Zirconium has been applied sucesfully in some formic acid applications but is sensitive to attack from acidic oxidizing chlorides and other contaminants such as FeCl₃ and CuCl₂ and the Use of zirconioum is not recommended in these media and these materials should be avoided¹. 
 

Tantaline's Imunity in Formic Acid up to 150°C

Tantaline is the only commercial available metal that is not sensistive to corrosion attack from formic acids in any concentration up to 150*C where impurities like FeCl₃ or CuCl₂ may be present.
 

Corrosion of Tantaline in Formic Acid above 150°C

Tantaline is showing very good corrosion reistance in formic acid acid at temperatures in the range 150°C to 300°C. The specific composition of the media will have to be evaluated to estimate the exact corrosion rate

References:

Ref 1: WahChang: "Zirconium in Formic Acid Applications" Technical Data Sheet no. ZirFor-007