10 Questions You Should to Know about Ductile Iron Pipe Fitting

2. Why are all Ductile iron pipes &#;painted black&#;?

The metal known as copper readily oxidizes when exposed to moist ambient air forming an egg-shell-thin yet highly protective green patina on its surface. The best example of this over time is the Statue of Liberty, located in the New York Harbor for nearly 200 years. Her &#;-inch thin original skin has not diminished over her significant time in the harsh marine conditions, mainly due to the naturally occurring patina.

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The simple fact is - oxidation is not rust. Rust is a destructive form of metal disintegration over time. Oxidation happens and then remains stagnant and protective of the substrate to which it is attached unless ambient conditions become more corrosive than oxidation can resist.

While the green patina of copper offers a highly desired visual appeal, the same oxidation process upon the surface of a Ductile iron pipe results in varied shades-of-cinnamon splotchy appearance upon its entire surface. This annealing oxide layer on DI pipe and fittings, much like the patina on copper, is so thin it&#;s barely measurable yet serves to prevent deeper pitting or degradation of the metal in standard ambient conditions.

The problem is, unlike copper, it's not attractive to the eye, and therefore, all Ductile iron pipes are coated with an NSF-61 certified asphaltic-based paint known as sealcoat. Water-based sealcoats are common today and are much friendlier to the environments of the foundry and the external world.

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What is the difference between Pressure Class and Thickness Class Ductile iron pipe?

When Ductile iron pipe was introduced to the market in , replacing cast or gray iron, pipe manufacturers agreed that there should be a standardized protocol for determining wall thickness. This standard included considerations to the inherent strength advantage of DI over its cast-iron predecessor. With assistance from the Ductile Iron Pipe Research Association (DIPRA), the pipe manufacturers began working towards an agreeable set of standards. 

While both Pressure Class and Thickness Class refer to a specific metal wall thickness of the barrel of the pipe, the primary difference is a change in terminology in how Ductile iron is classified under the specifications. Pressure Class designations refer to the pipe's ability to hold pressure, whereas Thickness Class refers only to wall thickness. These designations allow the end-user to specify a pipe that meets the design requirements of a given pipeline.  

Need more explanation on this topic? Check out this Iron Strong Blog with a video, What&#;s the Difference Between Pressure Class and Thickness Class, where Jeremy Gwin helps clear the confusion between the two terms and shows which iron pipe Class you should install on your next DI project.

Contact us to discuss your requirements of Ductile Iron Pipe Fitting. Our experienced sales team can help you identify the options that best suit your needs.