Stainless steel | Weld cleaning | Wednesday, 19 October 2022

Stainless steel rouging

Stainless steel is widely used in the pharmaceutical industry due to its high corrosion resistance and mechanical properties.

Despite this, pharmaceutical productions often face a major problem that is rouging of the stainless steel.

In this article we’ll cover what rouging is, why it occurs as well as proposing solutions to get rid of the problem.

What is rouge and what does it look like?

Rouge is one of the most common problems in pharmaceutical facilities and often occurs in high-purity water systems.

Rouging is a collective term that describes the reddish discoloration of stainless steel surfaces. It shows as pale orange or red/brown stains or almost black coatings depending on the environment and severeness.

Rouging is a form of corrosion that happens to stainless steel and needs to be removed to avoid further damage or contamination of the production. The most common type of rouging is a layer of red or red-brown coating covering the stainless steel surface.

Why does rouging occur?

Rouging is a form of iron contamination and often occurs in high-purity and hot water systems.

It is caused by various factors including low percentage of oxygen combined with high temperatures. In systems with high temperatures the risk of rouging is higher due to the iron oxides multiplying.

The risk of rouging also increases when there has been inadequate passivation, poor welding, oxides being present, or other inadequate surface treatments.

Why is it important to eliminate rouge?

In pharmaceutical production hygiene is crucial and therefore assessing the stainless steel equipment is an integral part of the production facility.

Rouge is a form of contamination and can cause bacteria build-up and contamination of products. The rouge can become detached from the metal surface and be carried by the liquid in a tank e.g. in the form of particles. This can result in the product being contaminated which is absolutely unacceptable.

How can rouge be eliminated?

Rouge is essentially not difficult to remove using the correct treatments. There are various ways of getting rid of the rouge and below we’ll explain two different options.

Contract derouging

Many pharmaceutical production facilities have their equipment derouged by external professionals. Contract derouging mostly involves chemicals being sprayed onto the contaminated stainless steel surface. The chemical needs to sit on the metal a while before being rinsed off and neutralized for the surface to repassivate.

The benefit of this is that you can have a standing agreement with the contractors to derouge your equipment once or twice (or whatever is needed) a year, and not worry more about it.

The disadvantage though is that it is quite expensive, and you might pay the same for a big tank with just a little rouge as you pay for a tank the same size with a lot of rouging. The downtime is always the same too, regardless the amount of contamination to be removed.

Electrochemical weld cleaning

No surprise that we here at Cougartron would recommend any pharmaceutical production getting their own electrochemical weld cleaning machine. Here’s why:

Instead of outsourcing the derouging, your internal maintenance team can easily operate a weld cleaner and deal with the rouging when needed or before the problem becomes so severe that it cannot be ignored.

Using a weld cleaner for derouging is a much quicker process due to the rouge being very easy to remove with this method. You can essentially remove it with one brushstroke and go on to the next area. This means that a maintenance team might be able to derouge and neutralize a tank during no more than one hour.

Using a weld cleaner can be beneficial for the regular maintenance to keep the inevitable rouging at a minimum.

Another advantage of the weld cleaner is that the investment in one machine is approx the same value as contract derouging of one or two single tanks. Meaning that your investment pays off very quickly.

How can weld cleaners be used for derouging stainless steel in pharmaceutical production?

When derouging with a weld cleaner we recommend our most powerful machine, the Fury200. This is ultimately the quickest way of derouging since you can use 4 brushes simultaneously.

The process of derouging is the same as weld cleaning any stainless steel surface. You simply dip your brush in the weld cleaning fluid and turn on your machine to get started.

Weld cleaning with our fluid (CGT 550) is completely safe for pharmaceutical production and the fluid is NSF certified meaning that it is certified and approved for use in pharmaceutical and food production.

Want to know more?

If you want to know more about derouging using an electrochemical weld cleaner, feel free to contact us using the form below.


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