In our previous post, we discussed beginner tips on choosing the right copper alloy.
Now that you’ve done your research, let’s take a look at major tips on fabricating and coating.
We’ll also cover mechanical joinery, welding, and aging, along with alternatives to copper alloys.
Fabricating copper alloys:
If you’re a first-timer, call on an experienced NOMMA fabricator before bidding your first bronze or brass job.
Brass and bronze cap rails are popular. When bending a copper alloy cap rail into a curve or helix, start by rolling it cold, as close as you can to the radius. Then clamp the cap to the channel and slowly heat the cap, clamping it into position every few inches. Be careful not to use too much heat or the copper alloy will ripple. You may want to use aluminum rail scrap cut approximately 1 inch long or beveled wood blocks to protect the brass cap from coming in to contact with the snap or C-clamp. You can also use aluminum bending forks to help shape the curve and helix.
The different metals in copper alloys among castings, extrusions, and brazing rods, burn off at different rates. That is why mechanical fastening may a be better method than welding for joining copper alloys.
Mechanical joinery is also suggested when clear coating only (not oxidizing) is specified on copper alloys because these materials should be pre-finished prior to assembly.
Welding copper alloys:
Welding C38500 and C65500 alloys: This process is recommended*: TIG Weld; Settings; DC Straight Polarity, Straight Argon Gas; Filler; Oxy Fuel Rod, Low Fuming Bronze, Non Flux Coated.
*Note that low fuming bronze rod is considered a brazing rod by some people in the welding industry and may not actually be a TIG welding rod. However, it offers good results when used in a TIG welding process for strength and color match. Low fuming filler rod seems to to be the most versatile for all copper alloys EXCEPT C65500 or silicon bronze. Note also, some fabricators find low-fuming or “bare” rod not so low fuming.
Welds on C38500 or architectural bronze may color at a different rate than the original material. Test out a sample piece and consider how to uniform the color with various finishing techniques.
Coating copper alloys:
When clear coating copper alloys, lacquer may not be the best choice. Lacquer coatings have a tendency to chip, allowing the exposed alloy to oxidize. Plus, once the lacquer coating chips, corrosion can creep under it. Wax may be a better alternative.
Additional Resources on Copper Alloys Coating Products and Suppliers:
Adsil – (Siloxane is specifically recommended as a glass-like coating with effective bonding properties to copper-alloy substrates)
Birchwood-Casey – (M24 Antique Black is specifically recommended for aging alloy C38500)
GJ Nikolas & Co. Inc. – (Their lacquers are specifically recommended for brass alloys).
Sur-Fin Chemical Corp. – (Brown patina-CB is specifically recommended for aging alloy C38500).
Triple-S Chemical Products Inc. – (Brown C-1 is specifically recommended for aging bronze handrails).
More suppliers: Suppliers listed here were specifically mentioned on NOMMA’s ListServ (2000–2005) in e-dialogue focusing primarily on copper alloys. This is not an exhaustive list. To find more suppliers mentioned on the ListServ, search the archives. Only NOMMA members have access to the ListServ and its archives. You can get access to the list by joining the NOMMA ListServ from the Member’s Only area of the NOMMA website (www.nomma.org). Once subscribed, you’ll receive information on accessing the archives and posting messages. Once you access the archives, you can search by topics, keywords, or for messages posted by particular NOMMA members easily.
Please share this post with others interested in beginner tips on fabricating and coating for copper alloys. Also, share your tips below in the comment box and visit our previous blog on How to Choose Copper Alloys.