Pump Impellers for HCl

Hi,

I have an applications where pump impellers are getting corroded badly from HCl in a mining type application. There are no solids or particulates in the stream when the HCl is in contact with the pump. We have tried a variety of materials including a PFA lined impeller and Hastelloy C276 but life I am getting is less that 6 months. The concentration is between 30-32% HCl at ambient temperatures. Would this be a good candidate for the Ultra-Metal or Ultra-Tough tantalum surfaces?

Thanks John Silva

Hello John,

It sounds like in you application you are struggling with the corrosion affects of HCl that is accelerated by erosion corrosion caused by your pump impeller. So lets first look at what was tried and why they failed.

Hastelloy C276 is likely suffering from an accelerated erosion corrosion in the 30% HCl. Like all corrosion resistant metals, the protective oxide layer is what allows the metal to be corrosion resistant. Because this is a pump impeller application that protective oxide layer eroded away more quickly and the base metal exhibits accelerated corrosion. This is common for high flow type applications with strong acids but it can be minimized or prevented.

The failure you experienced was with a PFA lining (Teflon lining) has to due with the fact that PFA liners are somewhat porous to HCl vapors. Once the HCl vapors penetrate the PFA liner its just a matter of time before the part fails.

In the case of Ultramet CPT's tantalum surfaces because tantalum has one of the most tenacious and well bonded oxide layers of any metal, the affects of erosion corrosion are minimized if not eliminated. Additionally the tantalum metal surface grown is not porous so HCl vapors will not penetrate it. In your application as long as there are not a significant amount of particulates in the solution so that they are sand blasting the impeller, the Ultra-Metal tantalum surface should work very well as this is a common type of application.

Thanks for your question,
Ultramet CPT Corrosion Experts