Last week we focused on the importance of pairing suitable galvanized hardware together, so what about weathering steel hardware?
One of the main things to recognize when using weathering steel hardware is that there are many limitations. There aren’t as many different bolt grades available, as well as fewer hardware pairing options.
So what’s the difference in weathering verses galvanized steel?
Well, galvanized steel involves applying a protective zinc coating to steel to prevent corrosion, while weathering steel also provides a protective coating, but the steel is allowed to rust in order to form the protective coating.
Another key thing to remember is that galvanized hardware should not be paired with weathering steel structures because galvanized steel is sacrificial by nature, meaning it will spread from the galvanized piece to the adjacent, unprotected steel, weakening the coating of the galvanized piece.
Some hardware is not available in weathering steel, but there is the option of using stainless steel (if the particular hardware is available in stainless steel). For example, a lock washer, which is locking device, does not come in weathering steel, but is available in stainless steel. The reason stainless steel can be used with weathering steel is because there is no coating and won’t negatively affect the weathering steel.
Bolt- headed and externally threaded fastener designed to be assembled with a nut.
Nut- An internally threaded product intended for use on external or male screw threads such as a headed bolt or a stud for the purpose of tightening or assembling two or more components.
Locking Device- a device used in conjunction with a fastener in order to positively lock the fastener, so that the fastener cannot work loose from vibrations.
Stud- a non-headed fastener.
Also, something else to point out is that you don’t typically see weathering steel in substations, but more in transmission and distribution. Weathering steel has a special patina, which if not careful when placing in an environment that has both wet and dry cycles, could continue to corrode and not stabilize.
There are weathering steel hardware options in ASTM A325 and A449 bolts, but not for A307, A394, A193-B7 and A36. For all thread studs, there are equivalents that can be substituted for the lower strength galvanized bolts. A490 bolt has the option of weathering, as well as black steel, and is an extremely high strength bolt, which is a good option as an equivalent to the galvanized A193-B7 bolt.
It’s also valuable to know the limitations with weathering steel hardware because there are no low strength nuts or square nuts, so a heavy hex nut would be used. Another limitation to note is that M.F. Locknuts are not readily available, and palnuts don’t exist in weathering steel. Feel free to browse our website for futher product and service information. www.distransteel.com