Nitric Acid-Free Pickling of Stainless Steel Beer Barrels

Jon Lawson

The Spanish manufacturer of stainless steel beer kegs, Entinox, has set up an innovative pickling and passivating line using a nitric acid-free Bonderite process. Benefits include superior health, safety and environmental (HSE) performance and extended bath life over traditional mixed acid pickling systems as well as outstanding corrosion resistance.

This is one of several examples of how manufacturers in Europe are benefiting from this process. It is designed for manufacturers that need to remove all scale, iron contamination and welding oxides from stainless steel to achieve a fully passivated surface with an even, clean and aesthetic finish.

Maintaining Food Industry HSE Regulations

In the food industry and for key products such as beer kegs, the surface must be totally free from any traces of pickling agents after the process. In addition, manufacturers face the challenge of increasingly strict HSE regulations on the release of potentially harmful substances, such as nitrogen oxide (NOx) emissions in the air and nitrate effluent in water.

Both were deciding factors in Entinox’s choice of the Bonderite C-CP 1300 pickling and passivating process from Henkel. The combination of high productivity and sustainability were its key criteria for investment.

What Is Bonderite C-CP 1300?

Bonderite C-CP 1300 is the latest generation of Henkel’s established nitric acid-free cleaning technology. In contrast to common mixed acid pickling systems, which are still widely used in stainless steel processing today, it requires no nitric acid to deliver excellent results. Additionally, it contains no citric compounds, which addresses the growing concern among brewers of residual flavours in the barrels.Eliminating risks

The process was developed to eliminate the risks associated with nitric acid in traditional mixed acid pickling systems. Nitrogen oxide emission from these systems can entail significant neutralisation costs and there is no viable way of removing nitrate effluents in wastewater. Both factors also limit the possibility of increasing the productivity of the pickling process without heavy investments in NOx and nitrate (NO3) ion removal.

Entinox kegs are normally made from 1.4307 (AISI 304L) grade stainless steel sheet, which is one of the most widely used austenitic chromium-nickel steel alloys. After bending, forming and welding, each keg has a surface of 2m2. Prior to pickling, the barrels are cleaned and degreased using Bonderite C-AK in a spray washer. Bonderite C-CP 1300 is then applied in another spraying step.

The manufacturer’s plant in Zaragoza has production capacity for up to 450,000 barrels per year and offers kegs in standard sizes of 20 to 50 litres as well as US gallon-sized products and various customised options.

“The pickling quality and efficiency that we achieve with Henkel’s process is outstanding,” comments Angel Roche, technical manager for Entinox. “While the resulting corrosion resistance is on a par with that provided by mixed nitric acid-based systems, Bonderite C-CP 1300 provides a considerably longer bath life and eliminates the risk of nitric fumes in the production area. And the absence of hexavalent chromium means that all effluent can be treated in our existing wastewater plant.”

Apart from kegs for transportation of beer to bars and restaurants, Bonderite C-CP 1300 has potential to achieve similar cost and environmental benefits in many other markets where stainless steel is processed. Examples span from heat exchangers and chemical process equipment to stainless steel devices and machines for the food and beverage industry as well as applications in the pharmaceutical and semiconductor industries.

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