Phosphate

The porosity of phosphate coatings allows the additional materials such as paint and dry film lubricants to seep into the phosphate coating and become mechanically interlocked after drying. The dielectric nature will electrically isolate anodic and cathodic areas on the surface of the part, minimizing under-film corrosion that sometimes occurs at the interface of the paint/coating and the substrate. The application of phosphate coatings makes use of phosphoric acid and takes advantage of the low solubility of phosphates in medium or high pH solutions. Iron, zinc or manganese phosphate salts are dissolved in a solution of phosphoric acid. When steel or iron parts are placed in the phosphoric acid, a classic acid and metal reaction takes place which locally depletes the hydronium ions, raising the pH, and causing the dissolved salt to fall out of solution and be precipitated on the surface. The acid and metal reaction also creates iron phosphate locally which may also be deposited.

Specification	Specification Description	Company
HP 4-7	Phosphate	Boeing
AMS 2480	Phosphate	General Electric
AMS 2481	Phosphate	General Electric
Mil-Dtl-16232	Phosphate	General Electric
AMS 2481	Phosphate	Honeywell
DOD-P-16232	Phosphate	Honeywell
Mil-Dtl-16232	Phosphate	Honeywell
TT-C-490	Phosphate	Honeywell
Mil-Dtl-16232	Phosphate	Sikorsky
SS 8416	Phosphate	Sikorsky
AMS 2480	Phosphate	UTC Aerospace Sys. - Collins Aerospace
AMS 2481	Phosphate	UTC Aerospace Sys. - Collins Aerospace
CP 14.08-01	Phosphate	UTC Aerospace Sys. - Collins Aerospace
DOD-P-16232, TYPE M, Z	Phosphate	UTC Aerospace Sys. - Collins Aerospace
MIL-P-16232, TYPE M, Z	Phosphate	UTC Aerospace Sys. - Collins Aerospace
PN 14.08-01	Phosphate	UTC Aerospace Sys. - Collins Aerospace
TT-C-490	Phosphate	UTC Aerospace Sys. - Collins Aerospace
MIL-DTL-16232, TYPE M, Z	Phosphate	Various

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