Bending After HDG

Hot-dip galvanized coatings are made up of a series of corrosion-inhibiting, highly abrasion-resistant zinc/iron alloy layers. To maintain this protective coating’s integrity, guidelines exist for bending parts after galvanizing:

  • Keep bend diameters as large as possible
  • Be careful not to bend to an extreme degree in relation to the article's diameter or section thickness, keep bend diameters a minimum of three times the section thickness
  • Bend galvanized reinforcement bars according to ASTM A767’s table
  • If possible, bend immediately after galvanizing, or when the part is hot

The speed at which the article is bent also may affect coating integrity. The galvanized coating is best maintained at slower bend speeds.

According to ASTM A767, some cracking and flaking of the galvanized coating in the bend area is not cause for rejection. Any flaking or cracking can be repaired as described in ASTM A780.

Minimum Finished Bend Diameters - Inch - Pound Unit

Bar No. Grade 40 Grade 50 Grade 60 Grade 75
3,4,5,6 6d A 6d 6d --
7,8 6d 8d 8d --
9,10 8d 8d 8d --
11 8d 8d 8d 8d
14, 18 -- -- 10d 10d
d=nominal diameter of the bar. Table taken from ASTM A767