HCl passivated

[siretb]

Hello,

I have heard about so called passivated HCl that is a blend of Formaldehyde and Hydrochloric acid.
I is used for cleaning of pipes, .....

I'd like to know how much less corrosive the HCl becomes, to steel, when formaldehyde is added.
Does it make a great difference to add the formaldehyde?

 

[NickE]

To my knowledge Nitric acid is generally used for passivation of stainless, along with Sulfuric for pickling.

 

[EdStainless]

I think that the word that you are looking for is inhibited HCl.

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Plymouth Tube

 

[siretb]

Thank you.
I knew that nitric is used for passivation.
What I try to determine is how effective formaldehyde is, a corrosion inhibitor that is added to what some European suppliers call "acide passivé", that is probabbly the same thing as inhibited HCl.
Would anyone have experience with such acids?