Hello, everyone. All spray package materials are susceptible
to corrosion. There are a variety of materials used
to fabricate spray packages:
Metals, such as aluminum, steel and tinplated steel (ETP)
• Aluminum spray package components are fabricated
from sheet metal or foil
• Steel and ETP are fabricated from sheet metal
Polymer coatings, such as epoxy, Micoflex, PAM, PET, etc.
Polymer films
• polypropylene
• double film layers, such as nylon on polypropylene
• (laminates)
Nylon used for valve bodies
Stainless steel used for valve springs
W. Stephen tait, ph.D.
Chief Science Officer & principal Consultant,
pair O Docs professionals, LLC
rustdr@pairodocspro.com
Corrosion Corner
Corrosion and spray
package failures
36 Spray October 2018
Metal corrosion is caused when valence electrons are transferred
from a packaging metal to ingredients in a formula. The
metal atoms become metal ions during their electron transfer to
formula ingredients; this changes the chemical states of the metal
atoms from atoms to ions as a result of the electrical transfer.
Thus, metal corrosion is referred to as electrochemical corrosion
because it is a hybrid reaction that has both electricity (electron
transfer) and a chemical change of state (atom to ion).
Polymer corrosion is a chemical degradation of a polymer
structure when formula ingredients absorb into the bulk polymer.
There can also be an electrical charge transfer with polymer corrosion
when ions and polar molecules absorb into and diffuse
through the polymer.
Consequently, corrosion is broadly defined as the degradation
of materials by an environment.
Aluminum aerosol cans Steel aerosol can