METHOD OF DETERMINING PROTECTION ABILITY OF CHROMATED ZINC COATINGS ON STEEL Russian patent published in 2007 - IPC G01N17/00 

FIELD: metallic protective coatings.

SUBSTANCE: method is realized by affecting coated test sample with salt mist for 12 h in a chamber at temperature 50±1°C and relative humidity 95±3%. Salt mist is created by spraying solution containing, g/L: NaCl 27.4, MgCl₂ 3.8, MgSO₄ 1.7, CaSO₄ 1.2, K₂SO₄ 0.9, CaCO₃ 0.1, and KBr 0.13. Sample is then aired at air flow velocity 2.7 m/s, subjected to UV radiation for 5 min, and held during 12 h in the chamber. Sample mass loss is determined in time moments before appearance of bulky zinc corrosion products and appearance of the first steel corrosion site. In the mass loss (g)-time (days) graph, straight lines are drawn specifically so that point of intersection thereof allows determining protection ability of chromate film on zinc coating. Protection ability of chromated zinc coating t^A _pr (days), taking into consideration operation location thereof, is found from formula: t^A _pr = (C^Y _Cl-/C^A _Cl-)t^y _n + 18(t^y _pr - t^y _n), where C^Y _Cl denotes concentration of chlorides in chamber, mg/(m²*day); C^A _Cl- concentration of chlorides in t^y _n protection ability of chromate film on zinc coating, days; 18 is empirical coefficient of seaside atmosphere of operation location; acceleration of corrosion in chamber; and t^y _pr time moment before appearance of the first steel corrosion site, days.

EFFECT: increased accuracy in protection ability determination.

3 dwg, 1 tbl