Ferrite pigments

Magnetic Recording Properties. Typical values of physical properties of barium ferrite pigments used in magnetic recording are given in Table 38. 

Table 38. Typical properties of barium ferrite pigments...

Only one zinc ferrite pigment has attained economic significance. Its properties are as follows [5.156] ... 

Toxicological reservations in connection with several corrosion protection pigments has led to the increased use of nontoxic pigments and to new developments such as 8icorin or the calcium or zinc ferrite pigments (see Table 5.9-15). 

Pigment yellow 119. See Zinc ferrite Pigment yellow 120 CAS 29920-31-8... 

Colortherm, Zinc ferrite pigment, Bayer Corp., Industrial Chemicals... 

Chromite and ferrite pigments have physical properties similar to those of the titanates and aluminates. Nearly all pigments of this variety are of brown and black shades, with just a few greens and green-blues. Some have unique infrared spectral properties that make them of interest in addition to their durability and color stability. 

Ferrite pigments have the general formula Me0 Fe203, where Me = Mg, Ca, Sr, Ba, Fe, Zn, or Mn. They are manufactured by calcination of metal oxides. The principal reaction is ... 

Ferrite pigments appear to protect steel both by creating an alkaline environment at the coating-metal interface and, with certain binders, by forming metal soaps. Kresse [70,80] has found that zinc and calcium ferrites react with fatty acids in the binder to form soaps and attributes the corrosion protection to passivation of the metal by the alkaline environment thus created in the coating. 

Sekine and Kato [81] agree with this soap formation mechanism. However, they have also tested several ferrite pigments in an epoxy binder, which is not expected to form soaps with metal ions. All of the ferrite-pigmented epoxy coatings offered better corrosion protection than both the same binder with red iron oxide as anticorrosion pigment and the binder with no anticorrosion pigment. Examination of the rest potential versus immersion time of the coated panels showed a lag time between initial immersion and passivation of approximately 160 hours in this study. The authors concluded that passivation of the metal occurs only after water has permeated the coating and reached the paint or metal interface [82]. The delay in onset of passivation could perhaps also be explained if, as in EBP, the protection... 

---