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How to Avoid Rust on Crown Corks: The Complete Guide for Craft Brewers

How to Avoid Rust on Crown Corks: The Complete Guide for Craft Brewers

Posted by Valentina @P-ink on 31.10.24

Rust on crown caps is a common problem, especially for craft brewers, where attention to detail and quality of the final product are paramount. In this article, we will explore the various steps in production that can affect the presence of rust on caps and how to prevent this phenomenon. From storage to capping to choosing alternative materials, this guide offers practical help for brewers seeking the best bottling experience.

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Use of stainless steel crown caps to prevent rusting

What Causes Rust on Crown Caps?

Rust on crown caps forms mainly due to moisture coming into contact with the exposed metal. The structure of the crown cap is composed of steel coated with a protective paint, with an internal plastic compound to ensure an airtight seal and preserve the contents. The cut edge of the cap is a vulnerable point, being exposed and unprotected, which increases the risk of rusting.

Steel crown cap structure with protective coating

Is Foaming Necessary for Craft Beer Bottling?

Foaming is a useful process to reduce air inside the bottle and prevent oxidation, but it is less common in artisanal bottling because the product is often bottled unfermented and therefore without foam.

Foaming process to reduce oxidation of bottled beer

How Does Capping Affect Rust Formation?

During capping, caps can suffer abrasion due to friction with the matrix, which makes them more vulnerable to rust. It is important to regularly maintain capping equipment, such as polishing the dies, to reduce damage to the caps.

Why is Rinsing Important After Bottling?

After capping, rinsing removes foam residue that may remain under the cap and cause corrosion. Effective water flow directed toward the ripples in the cap is essential, preferably with neutral water and a suitable nozzle configuration.

Rinsing system with water jets to prevent corrosion

How Can Adequate Drying Prevent Rust?

In addition to rinsing, drying is crucial to avoid corrosion. Compressed air should be used to completely dry the area under the cap, ensuring that no moisture is trapped. A system with a rotating conveyor belt and well-placed nozzles optimizes the drying process. If an air drying system cannot be adopted, it is still recommended to dry the bottles individually after capping.

Drying system to eliminate residual moisture under the crown cap

Are there Corona Caps that Don't Rust?

There are caps made of rust-resistant materials such as stainless steel and aluminum. Although these materials offer durability advantages, digital printing on stainless steel is not yet available, and aluminum caps are only available in 29mm size. Proper handling of standard steel caps, however, remains an effective solution to prevent rust.

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