urability of vitreous enamel coatings and their resistance to abrasion, chemicals, and corrosion

Despite all the positive aspects previously underlined, some issues limit the application of this type of vitreous enamel coating in many industrial fields. Vitreous enamel shows nonexcellent abrasion resistance, despite its superficial hardness, and this is mainly due to its brittle behavior.36,37 Abrasion is a very common mechanism of degradation of enameled surface, as fracture may occur and propagate,36 leading to loss of aesthetical properties, disclosure of the intrinsic enamel porosity, and loss of mass through the formation of flakes. Degradation due to abrasion negatively affects corrosion protection properties, as cracks can reach the metal substrate and allow a direct contact between the substrate and the aggressive environment.

This review focuses on the durability and degradation of vitreous enamel coatings, taking into consideration the external agents that can cause a relevant loss of their protective properties. Each section will consider a different property that makes vitreous enamel a coating of industrial interest, focusing on abrasion resistance, resistance to chemicals and detergents, and resistance to corrosion. The work highlights how these properties can be improved and examines the main scientific studies published in this regard. The review makes a critical analysis of the methods that are currently used to characterize these properties, highlighting their positive aspects and limitations as well. In conclusion, a discussion about the future perspectives of scientific research on vitreous enamel coatings will be introduced, showing possible research paths to be followed.

Enamel properties affecting durability

Vitreous enamel represents a particular type of vitreous enamel coating as it is made from low-cost materials, but at the same time it entails interesting technological properties. The degradation and durability of this vitreous enamel coating are key aspects to be taken into consideration when thinking about industrial applications. It is then necessary to investigate the external agents influencing the loss of properties of these vitreous enamel coatings and to study possible ways to improve their resistance and durability.

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The use of vitreous enamel coatings

Many reinforced concrete structures on Army installations represent critical assets that are vital to storing, maintaining and transporting vehicles and material needed to support the warfighter. Unfortunately reinforced concrete can have a short service life if the reinforcement steel in the concrete corrodes.

A series of new vitreous enamel coatings that contain hydraulically-reactive calcium silicates and aluminates have been developed to provide additional protection for the steel and to increase the service life of reinforced concrete structures. The new series of vitreous enamel coatings combine a layer of alkaline- resistant basecoat vitreous enamel
with an outer coating of vitreous enamel
that incorporates dicalcium silicate, tricalcium silicate and calcium aluminate and alumino-ferrite. The basecoat protects the steel while the calcium silicates in the outer layer hydrate when placed in fresh concrete and chemically bond to the surrounding concrete paste.

The bond strength between the concrete and steel is increased two to three times that developed with uncoated steel. The enamel over the steel produces durable corrosion protection. Tests with steel stay-in-place forms demonstrate the usefulness of the vitreous enamel coating steel.

This article comes from researchgate edit released