WG

When both internal and external surfaces are to be galvanized at least one filling and draining hole must be provided, with a vent diagonally opposite to allow the exit of air during immersion. Holes should be at least 50mm diameter for each 0.5 cubic metres.

 

 

 

Internal baffles should be cropped as illustrated. Manholes should finish flush inside to prevent trapping excess zinc.

When vessels and air receivers etc are not to be galvanized inside, 'snorkel' tubes or extended vent pipes must be fitted after discussion with the galvanizer, to allow air to exit above the level of molten zinc in the galvanizing bath.

Overlapping surfaces

Avoid narrow gaps between plates, overlapping surfaces and back-to-back angles and channels.

When small overlaps are unavoidable, seal edges by welding.

When left unsealed, small overlapping areas may trap pickle acid which can later escape to discolour or damage the galvanized coating.

 

 

 

Larger overlapping surfaces

If contacting surfaces cannot be avoided, a hole 6mm in diameter for every 100cm2 of overlap area should be placed in one of the members and the perimeter of the contacting area should be continuously welded. The vent hole in one member will ensure the safety of galvanizing personnel and prevent damage to the article.

 

Tubular fabrications and hollow structurals

Closed sections must never be incorporated. Provide vent holes at least 25% of internal diameter or diagonal dimension at locations agreed with the galvanizer.

Unwanted vent holes may be closed by hammering in lead plugs after galvanizing and filing off flush with surrounding surfaces.

Welded pipe section

Closed sections must never be incorporated. Sections should be interconnected using open mitred joints as illustrated at 'A' or interconnecting holes should be put in before fabrication as in 'B'.

Alternatively external holes may be positioned as in 'C', a method which is often preferred by the galvanizer, since quick visual inspection shows that the work is safe to galvanise. Pipe ends must be left open, or provided with removable plugs.

Small tubular fabrications

Small tubular fabrications must be vented, with holes not less than 6mm diameter.

 

 

Strengthening gussets and webs

Welded strengthening gussets and webs on columns and beams, and strengthening gussets in members fabricated from channel sections should have corners cropped or holed, (1) to prevent the entrapment of air in pockets and corners allowing complete access of pickle acids and molten zinc to the entire surface of the work, and (2) to facilitate drainage during withdrawal from acid and rinse tanks, and from the galvanizing bath.

 

 

End plates

Provide holes at least 13mm in diameter in end plates on rolled steel shapes, to allow access of molten zinc in the galvanizing bath and drainage during withdrawal.

Clearance for moving parts

Drop handles, hinges, shackles, shafts and spindles require provision of minimal radial clearances as detailed in the table below, to allow for the thickness of the galvanized coating.

Shaft or spindle size	Minimum radial clearance
Up to 10mm diameter	1mm
10mm to 30mm diameter	2mm
Over 30mm diameter	2.0mm to 2.5mm

Internal threads and nuts must be tapped oversize after galvanizing to accommodate the thickness of the galvanizing coating on the stud or bolt.

Australian Standard 1214 specifies the following oversize tapping allowances:

Nominal diameter of internal threads	Allowance
Up to M22	0.40mm
M24	0.45mm
		M27	0.50mm
M30	0.55mm
M36	0.60mm
M36-M48	0.80mm
M48-M64	1.00mm

Identification markings

For permanent identification use heavily embossed punched or welded lettering. For temporary identification use heavily embossed metal tags wired to the work.

Distortion Distortion can be prevented or minimised by: 1 Use of symmetrical designs 2 Use of relatively uniform sections 3 Use of accurately preformed members to avoid locked-in stresses 4 Use of balanced or staggered welding techniques to avoid locked-in stresses 5 Large open fabrications and tanks may require temporary cross stays to prevent distortion during galvanizing. Materials suitable for galvanizing All ferrous materials are suitable, including stainless steel parts and sound stress-free castings. Brazed assemblies may be galvanized, but check first with your galvanizer. Soft soldered assemblies cannot be galvanized.

Combination of ferrous surfaces Fabrications containing a combination of castings and other steels, and rusted or mill scaled surfaces, must be abrasive blast-cleaned before galvanizing. Weld slags Must be removed by chipping, griding, abrasive blast cleaning, flame cleaning or using a pneumatic needle gun. Provision for handling Work not suitable for handling with chains, baskets, hooks or jigs must be provided with suspension holes or fittings. If in doubt check with your galvanizer.