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Sound technical content, curated with aloha by
Ted Mooney, P.E. RET
Pine Beach, NJ

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Types of finishes that can reach 200 hour salt spray.

Our customer has asked for a finish that can reach a salt spray test of 200 hours.

Tom Hendrickson
job shop-manufacturer - Clackamas, Oregon
August 12, 2008

Hi, Tom. I remember a science class where the teacher said "peas are what, if you had a trillion of them, would cover the earth knee-high". The point was that it was an inadequate definition because many things, not just peas, met the definition. Countless coatings will meet 200 hour salt spray, so these things must come into it: appearance, substrate, organic vs. inorganic, adhesion, cost, conductivity, wear resistance, etc. Please tell us what kind of parts you are speaking of. Thanks!

Regards,

Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
August 13, 2008

Thank you for the feedback. The material is drawing quality cold rolled steel. Currently using yellow zinc chromate SC3 type II Fe/Zn 12 per ASTM B633. Customer wants 200 salt spray. Does it make a difference if a hexavalent yellow or non-hexavalent yellow zinc is used for the results in a salt spray test? What are alternate coatings for this type of material?

Tom Hendrickson
- Clackamas, Oregon
August 14, 2008

Hi,again.

Yes, modern proprietary trivalent chromates can meet that standard, Tom -- although they may involve or require a topcoat. Zinc alloy platings (zinc-nickel, zinc-cobalt, tin-zinc) will be even better. Electroless nickel plating can certainly achieve this rating although it may be too expensive or otherwise not suited to your needs. Good luck.

Regards,

Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey

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