Coating Designation and Corrosion Resistance for Mechanical Zinc

DesignationNominal Coating Thickness1st Appearance of White corrosion product (Hrs)1st Appearance of rust (Hrs)
Zn5 Clear5µm 24
Zn5 Bleached   24
Zn5 Black624
Zn5 Iridesent2448
Zn5 Opaque4672
Zn8 Clear8µm 48
Zn8 Bleached1272
Zn8 Black1248
Zn8 Iridesent4896
Zn8 Opaque72120
Zn12 Clear12µm 72
Zn12 Bleached2496
Zn12 Black1272
Zn12 Iridesent72144
Zn12 Opaque96168
Chromate Treatment 
TypeTypical AppearanceCorrosion Protection
ClearTransparent clear sometimes bluish tinge.Slight,for example against staining during handling or against high humidity in mildly corrosive conditions
BleachedTransparent with slight iridesence
BlackBlackwith slight iridesence
IridesentYellow IridesenceConsiderable, including organic vapours
OpaqueOlive green, shading to brown or bronze

Note: Due to the fact that fastening applications differ greatly, the above information is for guidance only and is correct to the best of our knowledge. The customer must satisfy themselves with the performance of the fastener and validity of the data. TR Fastenings will not be held responsible for any failure that may occur from the use of this information.