MIL-HDBK-1110
amphoteric). Inorganic zinc coatings have not been used often in
continuous water immersion because of concern for their limited
period of protection.
Inorganic Zinc Coatings
Advantages
Limitations
Can be low in VOCs
Needs clean, blasted surface
Excellent abrasion resistance
Requires skilled applicator
Excellent heat resistance
Constant agitation needed
Good atmospheric durability
Difficult to topcoat
Useful as shop primer
Attacked by acid and alkali
Costly
2.3.9
Zinc-Rich Organic Coatings. Zinc-rich organic coatings
utilize an organic resin rather than an inorganic silicate
binder. Zinc-rich organic coating films can be of the
thermoplastic (e.g., utilize vinyl or chlorinated rubber resins)
or the thermosetting type (e.g., utilize epoxy or polyurethane
resins). Film properties of zinc-rich organic coatings are
similar in most respects to those of zinc-free organic coatings
using the same resin. Organic zinc-rich coatings do not require
as high a level of blast-cleaned steel surface as do zinc-rich
inorganic coatings, and they are easier to topcoat.
Zinc-Rich Organic Coatings
Advantages
Limitations
Can be low in VOCs
equires skilled operator
Good durability
Constant agitation necessary
Relatively easily topcoated
Unsuitable for acid or alkali
Moderate surface preparation
Costly
needed
2.4
Coating Compatibility. Because of their different
chemical and physical properties, coatings of different generic
types or with different curing mechanisms are generally
incompatible with each other. Those of the same generic type or
with similar curing mechanisms are generally compatible with each
other. Table 1 lists compatibilities and incompatibilities of
different generic types of coating.
Another way to check solvent compatibility is to
determine its solvent solubility. To do this, soak a cloth in
methylethyl ketone or acetone, rub it against the existing paint,
and visually check for pickup of paint. The paint is classified
as "solvent soluble," if paint is picked up and as "solvent
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