Imagine a water-reactive, self-healing protective coating that avoids both the challenges of two-component systems and the over-release of corrosion inhibitors.
Dutch and Australian scientists say they have that answer.
Tested Corrosion Protection
The seven authors of “Self-healing anticorrosive organic coating based on an encapsulated water reactive silyl ester: Synthesis and proof of concept,” published recently in Progress in Organic Coatings, say they have tested their coating by multiple methods and have shown it to work, without the drawbacks of other current coatings.
The authors report that they have “synthesized a new water-reactive healing agent based on a silyl ester, encapsulated it, introduced it into an organic coating and tested its reactivity, protective principle and healing performance.”
The silyl ester “locally released at the damage site wets both the metal and polymer surface, reacts with moisture or water in the environment, and forms an adhered-to-the-metal barrier hydrophobic system which protects the metal at the scribe from further corrosion attack,” according to the article.
‘High Positive Impact’
Researchers say the concept “could have a high positive impact” on protective coatings technology, “due to the increased probability of incurring damage and the crucial importance of maintaining the potential of protection of the underlying substrate.”
The effectiveness of two-component
self-healing coatings, such as the
one shown at right, may be compromised
if both ingredients are not present at
the damage site at the same time and
in the required ratio, researchers say.
Self-healing materials have been a fast-growing research focus since the 1990s. The goal is to develop materials that mimic nature’s ability to repair itself.
In coatings technology, the self-healing concept has taken several paths, the journal authors say.
The most successful approach has been encapsulated reactive systems. But these, the authors say, have always employed two-agent systems—a drawback, “since the probability of having both ingredients present at the same time and in the required ratio at the damage site significantly limits the available options.”
A single-agent system able to react with the environment upon damage “would be a significant advantage, leading to a much more stable and guaranteed healing behavior,” they say.
The other main self-healing technology in protective coatings involves the incorporation of corrosion inhibitors, such as Cr-VI. These systems, however, are plagued by “excessive and uncontrolled release of corrosion inhibitors, even when the corrosion rate has already been reduced,” the authors say.
Avoiding Excessive Inhibitor Release
The team says its coating “may avoid further release of corrosion inhibitors from the crack sides when inhibitors are present.” It adds: “With this new approach, no crosslinker or catalyst is required, and the amount of material to be released can be reduced by being a surface reactive system.”
The authors say they tested the silyl ester in an epoxy coating using Fournier transform infrared spectroscopy (FTIR), electrochemical impedance spectroscopy (EIS), and scanning vibrating electrode technique (SVET).
The testing, they say, showed “the high capability of these techniques to be used in the development and evaluation of self-healing anticorrosive organic coatings and the good results in corrosion protection offered by the proposed silyl ester healing agent.”