Bolt Finishes
We all have seen chrome bolts or grade 8 yellow finish bolts or maybe a bluish silver bolt? What do the colors mean?
The different colors or finishes have nothing to do with the grade, they are merely for corrosion protection or cosmetic appearance. When you typically purchase fasteners such as bolts, nuts and washers the grade of the bolt has certain plating applied to them. When you buy a grade 8 bolt for suspension parts it is usually a yellow or gold finish called yellow zinc or yellow chromate. These two plating are similar but slightly different in appearance. Now don’t be fooled that all grade 8 fasteners are these two colors only. Some grade 8 comes with what we call a black oil finish not to be confused with black zinc or oxide. A black oil finish is the process a fastener goes threw during manufacturing of heat treatment. Also some grade 8 comes in a clear zinc or blue zinc finish. So the wise thing to do is always look at the makings on the head to be sure what grade you’re using.
Some of you may have seen SOCKETHEAD Allens with a black finish, these fasteners are grade 8 and are generally plated in black oxide or zinc. The black oxide is often a dullish finish as the black zinc has a higher gloss to it. Black oxide and zinc both have great corrosion properties but will rust.
Some of us like the look of black fasteners but don’t want the rusty bolt that will come with that finish after a few months in the weather.
Is their a black bolt that has a better corrosion finish?
Yes depending on the strength you require you can use stainless steel fasteners and plate them black zinc. We offer this to our customers who don’t want chrome or raw stainless and prefer the look of a shiny black bolt.
Chrome bolts often have the markings taken off during polishing and plating process, this can be a problem if you don’t know who you are buying from. It is always best to use a reputable source for your chrome needs. Chrome can come in two grades 5 & 8 and some times F911. At DMP Enterprises we only sell grade 8 chrome but offer grade 5 if that is what the OEM part requires.
Can someone take their own bolts and have those chromed, gold or black finished?
Yes, but there are a few things to look out for .One being if you are plating a fastener that is grade 8 or stronger it needs to be backed in an oven after plating. You are probably wondering “WHAT”. It’s called “Hydrogen embrittlement” and can occur in the fastener during plating. Hydrogen embrittlement is when gases trapped in the fastener which if not taken car of can cause failure in the bolt. Most plating shops are aware of this process of baking but will not do it unless you ask them to. At DMP we have all grade 8 bolts baked for 6-8 hours and a grade above that between 9-10 hours. This is still not a fool proof way of avoiding hydrogen embrittlement but it seems to work and has been the process for many years in the plating business.
