Specifier Galvanising Checklist

The achievement of a quality hot dip galvanized coating, for general and architectural use, is dependent on many issues, some controllable and some not. This checklist addresses the issues that can be controlled by the designer and those controllable by the galvanizer.

LEAD TIMES

In the case of large contracts, the galvanizer should be involved at the programming stage  with the fabricator and the end user. Hot dip galvanizing is normally the final process after  fabrication and prior to delivery and erection. If sufficient time for hot dip galvanizing, cleaning,  fettling and inspection is not provided in the overall programme, costly delays may occur at the  erection stage.

SPECIFIER GALVANISING CHECKLIST

Discuss requirements with Galvanizers Association and/or the selected galvanizer/s before designing commences.

The specifier or designer to ensure all steelwork contractors are  informed in writing of the architectural hot dip galvanizing requirements  prior to the finalization of the tender.

Make the requirements known to the galvanizer, in writing, together  with a sketch or sample, before placement of the order. Further  discussion with the galvanizer may be required.

Make use of the Association wall chart – “Design for Hot Dip  Galvanizing”

Choose correct steel type. If possible all parties related to  the project to purchase the specified steel from the same or specified  suppliers. Insist on the steel chemical analysis certificates for record purposes and issue copies to the galvaniser.

Ensure components can be dipped in a single immersion or  alternatively discuss the impact of double end dipping with the selected  galvaniser / Association.

Optimize size of filling, draining and vent holes

Optimize position of filling, draining and venting holes.

Should painting of the hot dip galvanizing be specified, ensure that  instructions stating “No passivation is required – substrate is to be  painted”, is handed to the galvaniser, at order stage, unless specifically discussed and excluded.

Select significant surfaces, highlight on drawing or sketch and discuss  with galvaniser / Association.

If necessary, hot dip galvanize a sample and establish acceptance /  rejection criteria.

Specify the correct temporary-marking pen for fabrication marking.

Ensure that if permanent marking, such as welded lettering is used it  will be appropriately hidden from final view.

If deemed necessary, to minimize handling damage ensure correctly  positioned lifting lugs are provided or if not acceptable, soft lifting slings  are used, by all parties, including the galvaniser, the transporter, the off  loader and the erector, etc. The use of the former is possibly more  appropriate.

Specify welding that is fit for purpose; do not allow over welding.

Should stick welding be used, ensure that all weld slag is  comprehensively removed by abrasive blasting or grinding prior to  delivery to the galvanizer. (Excessive weld porosity can have a marked  effect on the quality of the hot dip galvanized coating).

If the build-up of zinc at a weld is unacceptable for aesthetical reasons,  request that the correct welding wire or rod be used. Some welding  materials are reactive wrt hot dip galvanizing and can result in a thicker  coating on the deposited weld.

Simplify componentry – Simple structures – Better coating quality
Complex structures – Harder to manipulate in the galvanizing bath, more control, cleaning and fettling necessary.

Simplify complex structures by making use of bolting where possible or  alternatively design for after galvanizing welding, by using a suitable  mask such as “Galvastop”, which can be easily cleaned, successfully  welded and correctly repaired.

Discuss packaging / dunnage requirements with the galvanizer during  transport and ensure that ample site stacking facilities are provided. A  hot dip galvanized coating is applied in a factory and then transported  to site where frequently the components are thrown off the truck.  Inappropriate offloading may lead to unnecessary mechanical damage  of the coating. As the components are generally not wrapped, coating discolouration due to contaminants being deposited by wet trades, i.e.  angle grinding of wet clay bricks in the presence of hot dip galvanized  components, should be prevented.

Discuss the appropriate repair method, if repair is deemed to be  necessary, with the galvanizer. Silver spray paint is not acceptable. The silver spray paint may be initially more aesthetically acceptable  while the hot dip galvanized coating is shinny, but will ultimately stand  out and be aesthetically unacceptable, when the hot dip galvanized  coating begins to weather to a matt dull grey appearance. Furthermore,  most silver spray paints do not provide the same protection as a good  zinc rich epoxy for repair purposes.

Discuss the maximum size of coating repair allowable when alterations or adjustments are made on site, with the appropriate contractors.

Discuss inspection of the components prior to these leaving the  galvanizer’s premises.

Ensure that a certificate of conformance in accordance with the  specification, has been obtained from the galvanizer.

Ensure that selected galvanizers use their appropriate identification  paint, (if acceptable to the client) before delivering the components to  site. Furthermore, identification paint is to be applied only to areas  identified on the drawings by the architect or consultant or if not  available in non-significant areas, particularly if the component is not to  be over coated with a paint system.

Allow sufficient time for the hot dip galvanizing process to take place,  ideally 3 to 7 working days, unless other arrangements have been  made.