Difference between black oxide and zinc plated hardware?

[atikovi]

B.O.

https://www.grainger.com/product/10P799

Zinc

https://www.grainger.com/product/GRAINGER-APPROVED-Fully-Threaded-Rod-M14-2-Thread-10P808

Why is zinc 50% more expensive? Which has better corrosion resistance?

 

[paulo57509]

Not knowing anything about your application, I would go with zinc plated.

When I installed the SLP TPI intake runners on the IROC, they came supplied with black oxide SHCS. Took no time before these fasteners became horrible corroded (mostly cosmetic) from what ever moisture was in the atmosphere under the hood. Oddly, the black oxide fasteners GM installed on the lower intake have yet to become corroded. I'm thinking the black oxide coatings on each were applied with a different process.

When I upgraded the injectors, I replaced the corroded fasteners with 316 stainless fasteners.

 

[Spectre694]

Black oxide has minimal corrosion resistance. It mostly exists to prevent galling and cosmetic reasons.

Zinc has a higher corrosion resistance.

Cost is just because BO is cheaper to make than electro plating zinc

https://www.fastenal.com/products/attribute/600097/8#:~:text=Black Zinc,this is a good option.

 

[samven]

The Zinc plated should be more corrosion resistant and is normally recommended if it will be in contact with pressure treated wood. The problem is that the zinc coated use to be about 10% more than the black but the price of metals (copper, lead, zinc) has gone through the roof. Compare Black pipe to Galvanized pipe in the plumbing dept.

 

[jhellwig]

Granger prices are weird like that some Times.

 

[xspeedy]

Outside of color, zinc is more durable. I think it is more expensive though.

 

[atikovi]

OK zinc it is. They also have this cheaper zinc called Class 4.8. Whats the difference between this and the other zinc called Grade 2?

https://www.grainger.com/product/GRAINGER-APPROVED-Fully-Threaded-Rod-M14-2-Thread-25DM31

 

[Spectre694]

OK zinc it is. They also have this cheaper zinc called Class 4.8. Whats the difference between this and the other zinc called Grade 2?

https://www.grainger.com/product/GRAINGER-APPROVED-Fully-Threaded-Rod-M14-2-Thread-25DM31

Sae strength is in grade
Metric strength is class
Both the higher the number the stronger the bolt

Most Common ones are grade 2, 5, and 8 which are equivalent to 4, 8.8. 10.9. metric 12.9 is also pretty common and stronger than grade 8

https://www.fastenermart.com/understanding-fastener-grades-and-classes.html

 

[Trav]

Zinc coated are not very durable long term, cadmium plating is more durable and corrosion resistant, they are commonly used as a replacement under the car in high salt areas.

 

[atikovi]

Sae strength is in grade
Metric strength is class

Both are metric. M14-2.0

 

[Spectre694]

Both are metric. M14-2.0

Thread size and strength are separate measurements so there is no reason a manufacturer can't mix and match.

Sae grade is measured in PSI
Metric class is measured in MPa