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Pickling is a chemical cleaning process in which a strong acid is used to remove scale (mill-scale and/or weld-heat-tint), rust and other contaminants.
It effectively dissolves the surface, leaving the underlying alloy exposed. In the case of stainless steel, this means it is open to oxidisation and the formation of the passive layer, thereby optimising the corrosion resistance of the component.
We specialise in the pickling of tanks, vessels and pipework systems. From 304 grade stainless to super duplex grades and carbon steel, we offer a variety of chemical solutions and application methods that work within your time-constraints whilst achieving your quality requirements.
Passivation is often specified after the pickling of stainless steel. When the chromium within the alloy oxidises, it creates the chrome-oxide layer (or ‘passive’ layer) that gives stainless its corrosion resistant qualities.
Chemical passivation can do / mean one of two things. To paraphrase ASTM A967: i) Remove free-iron to facilitate spontaneous passivation by allowing (atmospheric) oxygen uniform access to the surface, or; ii) To provide an oxidising environment in which the passive film can be created in a controlled environment.
The passive layer is extremely thin and is vulnerable to attack from a variety of products – from ultra pure water, to orange juice and many others. In the interests of preventive maintenance, it is best practice to carry out a scheduled passivation process periodically to ensure your equipment is kept in good working order.
Many manufacturing processes create a slow build-up of residues within your equipment that will eventually reduce the efficiency of the process or even cause a complete blockage.
Calcium deposits, oil, burnt sugar, epoxy resins and a multitude of other products clogging up the pipes is a common industrial problem.
If you find yourself in this situation, give us a ring. If necessary, we’ll come and take a sample of the offending product, analyse it and come up with a bespoke solution. The costs of the chemical cleaning process are usually off-set very quickly due to the improved output of your system.
Similar to equipment used in enriched-oxygen service, hydrogen peroxide storage equipment should be very clean. Hydrogen peroxide is an unstable product, and an incredibly small amount of contamination within your plant can result in it decomposing, causing a massive liberation of oxygen.
At the very least, this will cause a significant increase in pressure which, in certain circumstances, can be devastating. We have had extensive experience working with the leading peroxide manufacturers and are well conversed in their chemical cleaning requirements.
As a minimum, thorough degreasing, passivation and stability-testing will be required. Contact us if you need assistance with your project.
