High aspect ratio to deliver anti-corrosion properties

The primary function of anti-corrosion coatings is to protect steel structures against corrosion and chemicals. The industry uses predominantly two-component epoxy coating as the anti-corrosive protection layer. They do so in particular for steel structure corrosion protection in the most severe environmental conditions. MicaFort mica improves the function of these industrial protective coatings.

MicaFort as an anti-corrosion coating additive in paint

We produce MicaFort from the naturally occurring minerals, Phlogopite Mica and Muscovite Mica. These minerals have several properties that altogether make it unique in its features for use in a metal coating:

• a very high aspect ratio,
• a narrow particle size distribution,
• retaining of platy particles even after processing to an ultrafine powder,
• lower density,
• lower weight,
• and lower formulation costs compared to commonly used platy fillers.

In general, flat, platy particles overlap in a film and prevent water, oxygen or other chemicals from reaching the metal basis directly. This behaviour means that the time for corrosion stimulators to start their work will increase. The addition of such platy additives ensures optimal performances for surface protection in these paints:

• rust prevention
• anti-corrosive
• and concrete

Testing MicaFort in corrosion-resistant coatings

During an extensive testing programme throughout 2015, MicaFort in corrosion-resistant coatings were tested. We aimed to show the differences in the corrosion protective performance of Phlogopite and Muscovite Mica compared to other platy mineral fillers in a barrier coating.

The tests have been run by Electrochemical Impedance Spectroscopy (EIS) method and salt spray testing. The first mentioned has recently been introduced as a fast and reliable method to assess the anti-corrosive properties of a coating system. To prove the results, LKAB Minerals Research and Development team has also conducted extensive and time-consuming salt spray testing, fortunately producing the same results. For this test we incorporated the mineral filler only into an intermediate coat.

EIS Testing results

Salt Spray Testing results

As the above results overview shows, the type of mineral filler has a strong influence on the anti-corrosive properties of the coating. Compared to the reference, where they did not use a lamellar filler, some formulations containing these have similar anti-corrosive performance. However, Electrochemical Impedance Spectroscopy clearly shows the advantages of both Phlogopite and Muscovite Mica. Moreover, especially the newly developed grade MicaFort MM75, a Micronised Muscovite grade shows a significant performance increase of the anti-rust coating. MicaFort MM75 is a very fine Mica product with a particle size top cut of 75 microns (D₉₈).

MicaFort mica in a metal coating

We decided to omit the use of a primer and topcoat for this study, and we did not use any other anti-corrosive pigments or additives. Therefore, it was interesting to see that by applying only one coat of an epoxy paint containing MicaFort the C5-M class of anti-corrosive behaviour optimisation. We expect that by optimisation, i.e. including a primer and topcoat, plus incorporating active anti-corrosion additives, one can further improve the corrosion resistance.

Micronised Muscovite Mica, in this case especially MicaFort MM75, is topcoat well suited for anti-corrosive properties due to its well-defined shape and morphology.

Get in contact with us if you want to know more or have additional questions about our MicaFort in anti-corrosion coatings by finding your local contact in the contact field at the bottom of this page.