Written on: September 1, 2016 by W. Stephen Tait
Hello, everyone. Spray packages and spray valves are fabricated from a variety of materials, such as:
Corrosion is a complex surface phenomenon that causes degradation of spray package materials. Spray package corrosion requires materials, such as metals and polymers; a surface and a corrosive environment (ingredients in your formula).
Material degradation could produce unwanted effects such as leaking packages, packages that stop spraying, product malodor or discoloration. Polymer coating or laminate film corrosion could produce pieces of polymer that clog spray package valves. Plastic bottle and plastic can corrosion could cause packages to become brittle, panel or lose their strength and burst under pressure.
All types of spray package materials are susceptible to corrosion. For example, electrochemical corrosion causes package metal loss that could lead to:
The occurrence of corrosion is difficult to predict because there are numerous factors that contribute to and/or cause corrosion. In addition, several of these factors often interact synergistically with others to cause corrosion or make corrosion go faster. The probability of corrosion occurring and the rate of corrosion are determined by:
Water and package materials are thermodynamically unstable when exposed to each other, and almost all formulas have some water in them, even if only as very small amounts from contamination. Consequently, corrosion of spray package materials is always a possibility.
Various formula ingredients—besides water—cause or contribute to spray package corrosion:
Extremely low corrosion rates don’t produce enough corrosion to reduce the service lifetime of the package materials. Very high corrosion rates produce corrosion that significantly reduces package service lifetime and degrade product efficacy. Thus, the corrosion rate determines if spray package corrosion will lower spray package service life to an unacceptable length.
The variety of corrosion-causing factors, their number and possible combinations make predicting spray package corrosion difficult without corrosion data. Predicting package material corrosion rates without data is also not possible at this time. Consequently, corrosion testing is recommended for all new formulas and derivatives formulas and alternate packaging for existing formulas.
A few corrosion-guidelines to consider when developing formulas or derivative formulas:
We would be happy to teach our Elements of Spray Package (Aerosol Container) Corrosion short course at your R&D facility. We have also introduced the Corrosion Partnership Program, which makes our electrochemical corrosion laboratory, corrosion consulting and anti-corrosion technology conveniently available for your R&D program. Contact: email@example.com; 608-831-2076; www.pairodocspro.com. Back articles of Corrosion Corner are available from Spray. Thanks for your interest and I’ll see you in October.