Alkaline base descaler to replace HCL
Alkaline base descaler to replace HCL
(OP)
Hi all,
In order to enaure zero hydrogen evolution during the descaling process of screws (material is Chrome Molydenium Alloyed steel, SCM435, through hardened and tempered to property class 8.8), I'm looking for an alkaline base descaler which is suitable to replace HCL. Can anyone recommend?
Thank you,
ct
In order to enaure zero hydrogen evolution during the descaling process of screws (material is Chrome Molydenium Alloyed steel, SCM435, through hardened and tempered to property class 8.8), I'm looking for an alkaline base descaler which is suitable to replace HCL. Can anyone recommend?
Thank you,
ct





RE: Alkaline base descaler to replace HCL
Also give the quanity you need to descale.
Where are you located.
RE: Alkaline base descaler to replace HCL
I'm in Malaysia.
RE: Alkaline base descaler to replace HCL
An oxide scale has negligible solubility in alkaline solutions, the only way they can be very effective is as electrocleaners (e.g., Oakite 90), which forms gas bubbles at the solution-metal interface and can partially get underneath and mechanically lift of the scale. Not effective if you have a smooth hard heat treat scale.* Even then, it is more effective to alternate between anodic and cathodic (only cathodic causes H at the metal).
*Better to avoid scale formation in the first place!!
You can add an inhibitor to HCl or sulfuric acid, such as one of the 'Rodine' products from Henkel, which will greatly minimize the hydrogen embrittlement risk. But, some inhibitors interfere with some plating processes, so best to check with the supplier first (I think no problem for black oxide, though).
http://www.henkelsurftechna.com/
Another brand is 'Pickle Pal' from Columbia Chemical:
http://www.columbiachemical.com/
RE: Alkaline base descaler to replace HCL
There are several options available to you.
Fix you heat treating facilities to prevent/minimize the scale. This is better option.
Same acid + inhibitor
Change acid + inhibitor, this might be problem depending on the type scale.
Acid Mix + inhibitor, again depending on your scale.
(Inhibitor meaning a complete package of inhibitor, wetting agent, rinse agent, etc.}
Electrolytic, very high initial cost. Maybe a problem depending on your scale.
The rust removing ability of alkaline products is very limited and is primarily used for removal of "flash rust". Alkaline cleaners though much better for the metal require much more attention as far as the maintenance of the bath and rinse system.
No matter what system you use, The proper maintenance of the baths is essential.
As stated get with a supplier of pickling materials and discuss your problem with him. You will need a technical representative not a salesman. When we mixed our acids we used the Rodine products with great success. If i remember it was Rodine 92 for HCl.