Steel phosphate coatings

Parkerizing A trade name for a process for phosphate treatment of steel. See phosphate coatings. 

Modified Zinc Phosphates. Coatings on steel have been identified as hopeite, 4H2O, phosphophyUite, 4H2O, and... 

Dichromates and chromic acid are used as sealers or after-dips to improve the corrosion resistance of various coatings on metals. Eor example, phosphate coatings on galvani2ed iron or steel as well as sulfuric acid anodic coatings on aluminum can be sealed by hexavalent chromium baths. 

Fig. 32. Micrographs of microcyslalline zinc phosphate coatings on (top) A514 and (bottom) A606 steel substrates showing the very different morphologies produced by identical processes [54],...

It has been suggested that the zinc phosphate coating has the composition Zn3(P04)2 Zn(0H)2, but X-ray diffraction studies have given very good correlation between Znj(P04)2-4H2 0 and the zinc phosphate coatings on steel . 

Table 15.12 Typical uses of phosphate coatings on steel ...

X-ray Diffraction Study of Zinc Phosphate Coatings on Steel , US Department of Commerce, Office of Technical Services, Rep. No. PB 111, 486 (1954)... 

B.S.l. Phosphate Coatings (Drafting) Panel, Phosphate Coatings as a Basis for Painting Steel , J. Iron St. Inst., 170, 10 (1952)... 

The protective value of a phosphate coating is enhanced by a dip or rinse in an acid chromate solution. Joint Service Specification DEF-29 makes such a rinse mandatory for steel parts treated by an accelerated process, and optional after treatment by a non-accelerated process. Details of rinses are given in Section 15.2 (Table 15.10, p. 15 30). 

With. The following table, compiled from Refs 1, 2, 3 6, details the compatibility of dry expls (0.2% moisture max) with metals commonly used in military hardware. For all of the listed metals, exce] t phosphate coated steel, intimate contact was maintained with the various expls at ambient temp for a two year period (Ref 2). Phosphate coated steel was exposed for six months at 71° (Ref 3)... 

Exposure of moist expls (0.5% moisture) with common metals at 50° for two years (two months at 71° and 100% relative humidity for phosphate coated steel) resulted in from very slight to very heavy corrosion for practically all of the metals shown in the above table. Stainless steel was unaffected by any expl, acid proof black painted steel was not affected by 75/25 Tetrytol and 50/50 Pentolite, and Mg-Al alloy (Jl) was unaffected by BkPdr. Phosphate coated steel exhibited considerable corrosion with BkPdr, but was unaffected by TNT, RDX, Comp B, Tetryl or 50/50 Pentolite (Ref 3)... 

Phosphate conversion coatings provide a highly crystalline, electrically neutral bond between a base metal and paint film. The most widespread use of phosphate coatings is to prolong the useful life of paint finishes. Phosphate coatings are primarily used on steel and galvanized surfaces but can also be applied to aluminum. Basically, there are three types of phosphate coatings ... 

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