Anti Corrosion Coating

[istech]

Dear Forum,

I am seeking advise on a corrosion coating application. We will be using a twin wire arc spray system. The component in question is as follows:

A 4 in X 26ft long round mild steel with a 16in X 16in base plate on one end. They are used in the fish farm industry in our area. These poles are set 30 feet apart with a stiff wire attached at the top and strung between all the poles. Fish pen nets are then hung here to be cleaned and dryed.

They will be subject to salt water spray and near a salt water environment.

Questions are:
1. Recommended coating material
2. Coating thickness
3. Type of sealer after application, which I presume I will need to do.

Any help is greatly appreciated.
Thanks

Dale Finnerty
Industrial Surface Technologies Inc.
British columbia, Canada

[Stuart Milton]

Hi Dale,

Normally for saltwater / coastal environments, Aluminium would be the recommended coating.

Thickness is dependent on what life to first maintenance you would require. According to European Standard BS EN ISO 14713, you should apply 150 microns (6 thou) of sealed, sprayed aluminium to get 20 years life to first maintenance in seawater splash zone environment.

For a standard seawater sealant, you could use just a thin epoxy sealer. Suggest you talk to the paint manufacturers for their recommendation. Not sure if you may need to consider a different sealer dependent on what may be washed off the nets.

Hope this helps.

[Gordon]

Hi Dale

to the Surface Engineering Forum.

I will go along with Stuart on this one

[istech]

(09-12-2008 08:52 AM)Stuart Milton Wrote:  Hi Dale,

Normally for saltwater / coastal environments, Aluminium would be the recommended coating.

Thickness is dependent on what life to first maintenance you would require. According to European Standard BS EN ISO 14713, you should apply 150 microns (6 thou) of sealed, sprayed aluminium to get 20 years life to first maintenance in seawater splash zone environment.

For a standard seawater sealant, you could use just a thin epoxy sealer. Suggest you talk to the paint manufacturers for their recommendation. Not sure if you may need to consider a different sealer dependent on what may be washed off the nets.

Hope this helps.

---

Thanks Stuart,

From what I have heard spraying Aluminum you have to be cautious with ventilation as its can ignite? We have a wire that is 85% Zinc 15% Al. How would that hold up or would you still recommend straight Al? Thanks for your help.

Dale

[Stuart Milton]

Hi Dale,

There is some truth in what you have heard that Aluminium can be a bit more reactive than zinc or zinc/al alloy.

As mentioned, typically, saltwater applications use aluminium but in the standards, pure zinc is also specified. ISO 14713 suggests 250 microns (10 thou) of sealed sprayed zinc as an alternative to aluminium for the same life to first maintenance. In the grand scheme of things, zn/al alloy is relatively new and hence is not specifically mentioned but a coating of 200-250 microns (8-10 thou) would work out OK. Choice of sealer same as before.