Painting of galvanized pipe

[alpo0]

I need to protect sprinkler piping against corrosion under the pier/wharf. I am definetly going to use galvanized pipe.
What do you think about painting the pipe as additional protection against the corrosion?

 

[abeltio]

i would use standard pipe with a marine paint scheme... like with ocean going ships.

saludos.
a.

 

[Rich2001]

Use a phosphoric acid based cleaner on the galvaning such as Galvaprep

http://www.buyhstna.com/docs/234451.pdf

prior to painting. Following this with an epoxy based coat then ultimately a polyureathane top coat. Many Bridge are coated with this scheme.

Vita sine litteris mors est.

 

[JStephen]

Depending on the size of the pipe...it might be cheaper to go to stainless than to paint the galvanized.

 

[jonesey]

if we are talking salt water in this pier/wharf area i would stay clear of stainless steel. Salt, chlorides and stainless steels do not generally go well together. Have you thought about using some of the non-metallic piping that is available such as Ameron etc. this pipework is also firepoof tested and is also used on off shore installations.

 

[alpo0]

Thanks everyone for help.
The environment is sea water. The piping has to be listed for the fire sprinkler service. It looks like the best choice is what Rich2001 proposed.

 

[stanier]

You shpuld serious consider CPVC or 316 ss in this environment. If the paint system is not renewed when it comes to being used you may find that the system fails. Do you want a preventable death on your conscience even if you dont get sued or go to jail?

 

[alpo0]

Stanier,
1. CPVC is not listed for exposed instalation in Ordinary/Extra hazard occupancy.
2. There is no CPVC pipe biger than 3" listed for fire sprinkler service.
3. As per Jonesey, SS is not durable in salty environment.

 

[stanier]

There are grades of stainless steel that are eminently more durable in a coastal environment than painted galvanised steel. Go to

http://www.nidi.org

and check it out.

In SE Aisia ABs from tyoc (made in Australia) is used for fire protection of Kampongs and other structures. Esso weven use it on rigs. This material is available up to DN800 Class 15.

http://www.tycowater.com.au/water/products/plastic_pipeline_systems/plastic_products#ABSDuraFree

 

[Gadge]

Is this a replacement of the original system? If so, check the original design spex.

Is this a new instalation? If so, check the local fire regulations for spex (if applicable).

Is the environment salt or fresh water? This will give you two options for suitable materials.

If you must use galvanized pipe, I take it that the connections will be threaded. The primary corrosion areas will be around the connections.

Will this be using fresh water or sea water?

Will the piping system be exposed to immersion (coastal weather conditions or tidal)?

Is cost a major factor?

Will this be a supply on demand or dry flood system?

What is the volume of flow required for this system?

What type of shipping will be using the berths?

Will regular, qualified inspection be carried out?

When you have figured out these specifics, it will help you focus on suitable materials.

Galvanized pipe may be suitable, you will need to take into account galvanic action and possible isolation fron the pumping system to allay this, or will the supply be gravity feed?

Protective coating systems are available for this sort of material. Keep in mind that all coating systems require proper periodic inspection (including galvanised).

SS, cunife and other corrosion resistant metals provide lower maintenance, high instalation cost is a draw back.

PVC pipe? Not exactly fire proof.

RTR pipe is good for brine environments, make sure to specify UV stabilised.

If you must take the cheapest option, galvanized piping with an approved protective coating system (see Hempel for example), may fit your needs.

 

[stanier]

You may save money by using dairy tube rather than Sch 10s stainless steel. For large headers use spiral wound stainless steel. It proves cheaper than painted galvanised steel when you take into account the installation cost.