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HCl reacts furiously with Zinc (Galvanize), and reacts rapidly with steel (pickling

process). Even when neutralized, the Cl is still reactive towards both Zinc & Steel,
and will, in a short period of time, completely remove the Zinc and start rusting the
steel if not copiously rinsed and dried, and even re-chromated. Big hassle in the
field. As for Stainless Steel cable, even 316L is not recommended for wet Chloride
service. You must use a Molybdenum stainless such as 317, or other such Moly
containing alloy such as Haynes C276. They are not as strong but will withstand the
wet chloride environment.

Another option is Tin plated cable instead of Zinc. Tin holds up much better than
Zinc in chloride. Platers know that you strip Tin in Fluoboric/peroxide mix; HCl won't
do that job. But as the cable is used It will get scratched & abraded, so any coating
will eventually give out and put whatever depends on that cable at risk. Therefore
the correct grade of material should be selected for the intended service.

Dave Kinghorn
Chemical Engineer


Hydrochloric acid (HCl) concentration

The concentration of hydrochloric acid (HCl) is calculated by measuring the
conductivity and temperature of the acid. Valmet offers readymade concentration
measurement recipes for various hydrochloric acid concentrations.

the measurement.

Valmet Concentration measurement is m

aintenance free and accurate thanks to 4 electrode technology. The sensors are
designed to withstand rabid temperature changes have a long lifetime even in the
most demanding applications.


Materials PTFE and W 1.4404 (AISI 316L)

Pressure 12 bar at 120o

Temp. Sensor Pt 1000 (IEC 751 class A)

Solution Measuring Range Temperature

HCl 0-15% 10-80 oC

HCl 25-40% 0-60 oC

HCl 30-60% 15-45 oC

Hydrochloric acid is often used for cleaning steel prior to galvanizing, and at typical
strengths of 3-15%. Its common to start a new tank at a high strength (say 15%)
then as the tank ages the acid concentration reduces as it converts iron oxides to
iron chloride.
But HCl concentration is not the only important parameter. Concentration of iron
chloride is also important, as well as temperature.
Prof Kleingarn did a lot of research on this and produced a graph of concentrations
of HCl and FeCl2 to enable operators to optimise pickling time.

Geoff Crowley
galvanizing & powder coating shop
Glasgow, Scotland