Surfaces such as metal and other corrodible surfaces are often exposed to extreme weathering, temperatures, moisture, impurities, and otherwise damaging external forces that accelerate corrosion. Conventional methods of corrosion protection include applying paints and other coatings, such as petroleum-based undercoatings, with a sprayer to the exposed surface. To be effective, the entire exposed surface must be covered or the corrosion process will be accelerated at the unprotected areas. While open-area surfaces may be easier to protect, those surfaces found in internal cavities within an overall framework can be more challenging to protect. Achieving full coverage on internal surfaces can be extremely difficult, and in some cases impossible without drilling several access openings in the structure. These extraneous openings can compromise the strength of the structure as well as create more entryways for water and debris. This increases the opportunity for corrosion to initiate at the edges of the openings.
Another method for protecting enclosed surfaces from corrosion is by using vapor phase corrosion inhibitors (VCIs). Under atmospheric corrosion conditions, the method consists of saturating an enclosed surface with chemical vapors that enhance the corrosion resistance of the metal surface. VCIs are typically used for corrosion prevention of sealed hollow structures, but have been used in some paint formulations. Corrosion-inhibiting pigments in paint primers provide protection by reacting with the absorbed moisture vapor to passivate the metal surface to reduce its corrosive characteristics. VCIs aim to protect the metal surfaces primarily by changing the kinetics of the corrosion reaction without adversely affecting the material properties of the metal itself. Gas phase corrosion inhibitors offer no barrier protection because if the surfaces being protected are not completely enclosed from all sides, the inhibitors can be easily washed away with the introduction of water, etc., and the protection will be short lived.
There remains a need for a process and a corrosion-inhibiting composition that provides corrosion protection; for example, to underlying metal (corrodible) parts and structures that are difficult to access for corrosion protection. Moreover, there remains a need for a singular corrosion-inhibiting composition that is protected from being washed away, and that results in improved adhesion qualities between it and the underlying corrodible surface to allow for maximized corrosion protection, thereby overcoming the deficiencies of the prior art methods and systems.
A patent-pending, self-expanding, polyurethane foam containing either organic or inorganic corrosion inhibitors was developed. The technology is especially useful for application in hollow or sandwiched metal structures.
The anti-corrosion foam is compatible with a range of existing polyurethane foam chemistries and delivery methods. The technology holds the potential to tailor formulations of VCIs and foam systems to match the specific application, such as the differing corrosion inhibition requirements of aluminum vs steel.
The foam maintained 91% of adhesion strength after 500 hours in a salt fog test, whereas standard foam maintained only 55% (see figure). It is compatible with a variety of commercially available corrosion inhibitors, as well as various commercially available foam formulations and delivery systems.