Corrosion resistance of zinc plated, cadmium and old yellow plating with help of salt spray test
Our zinc plated steel parts (partnumber ends with "Z") have a corrosion resistance that is measured with a salt spray test.
the old yellow zinc plating had following values: after 48 hours - white rust - after 120 hours red rust (the zinc plating is done electrolytical zinc plated and not thermal zinc plated)
The cadmium plated parts are only 96 hours guaranteed we can confirm that the HGR-Series & MTH is produced after AMS-QQ-P-416 which contains the following point: 4.6.3 Corrosion Resistance (Production Control Test) Corrosion resistance shall be conducted in accordance with ASTM B 117 (salt spray test) for 96 hours or, for fastener hardware, in accordance with NASM1312-1. To secure uniformity of results, Type II supplementary coatings shall be aged at room temperature for 24 hours minimum before subjected to the salt spray. We have no own tests, but if needed we can do those test for a price of 500 € per Article. the issue is that the cadmium plated parts will probably be better then the new "Z" zinc plating in terms of corrosion resitance, but it is not guaranteed. An american test has been done using different standards, which lead to a result of 96 hours. Another thing is that Cadmium plating is self healing, it performs like Aluminium, so this means if you make a scratch, it will self heal, whereass "Z" does not do this, a scratch will have rust occur on that spot. (a bit the same acting as Aluminium)
ZN If you have a project with a quantity higher then 2500 pieces, then we can also propose ZN protection which contains zinc and nickel , there white rust starts only at 240 hours, and parent corrosion only at 720 hours, this protection is used in the truck market a lot. The downside is the look of it. It has a matt grey surface that does not look as good as other surfaces. having said the above, it is not hard rocket science, the surface, from of a part can influence the performance. The spring of the stud will have a different result for instance then the spring cup of the HGR series.
Here are the test results of the new Z plating: the test is made by visual inspection at certain time intervals, while a salt spray is applied on the parts. The salt spray is at a temperature of 35°C+/-2°C and at a condensation start of 80cm² (1,5 +/- 0,5) ml/h NaCL concentrate (50+/-5) g/l, with PH 6,5 to 7,2 the state of which the part is is determined by a value after a visual inspection and an estimate value of how much surface is affected.
value Visual interpretation
A no change
B stains apear
C black dots apear
D very light or moderate discoloration
E mat colored between light and strong
F strong mat colored
G very light view of corrosion -white rust
H strong view of corrosion white rust
K corrosion with holes
L ground material corrosion – red rust
Value surface impacted
0 no defect
1 one small defect observed
2 1-5% of surface involved
for the "Z" new style zinc plating we have following results:
First test: You can see with the first test results that after 120 hours value A which means nothing happened ; this means parts can be approved for 120 hours corrosion proof on the salt spray test 168 hours value B stains appear 216 hours value G3 which is a very light view of corrosion only affected for maximum 10% of the surface of the part 240 hours this is still the same, and not yet the level of L6 ,so it can be safely said that after 240 hours salt spray test the parts start to rust, so it’s even with a big safety factor
Second test: 120 hours value A which means nothing happened ; this means parts can be approved for 120 hours corrosion proof on the salt spray test 168 hours value G3 which is a very light view of corrosion only affected for maximum 10% of the surface of the part 216 hours value G4 which is a very light view of corrosion only affected for maximum 25% of the surface of the part 240 hours this is still the same, and not yet the level of L6 ,so it can be safely said that after 240 hours salt spray test the parts start to rust, so it’s even with a big safety factor
conclusion: "Z" is guaranteed 120 hours first white corosion "Z" is guaranteed 240 hours first red corrosion (parent material)
certification of The Zinc plating is according to standard DIN EN 10204 2.1
typical ZN HK10 > 8µm + vers.