1. Piping Failures

A piping failure is often the first sign of a corrosion problem. Yet in many examples, signs of an impending pipe failure have been evident for months or years, and gone ignored. Failures can be minor (in the form of a pinhole leak) or catastrophic, with significant losses due to water damage as well as the cost of pipe replacement.

2. Pipe Repairs

Pipe repairs take on various forms, ranging from temporary clamps to the replacement of entire piping systems. In many examples, the denial of a corrosion problem results in multiple or staged repairs over years, wasting valuable time that could have otherwise been used to correct the problem and minimize far greater corrosion damage. All too often, one or multiple individual failures are fixed without further investigation into the hidden cause.

The absolute reliance on favorable but typically inaccurate corrosion rate data presented by corrosion coupons, often in contrast to blatantly obvious physical indicators such as thread leaks and high rust deposits, allows a high corrosion condition to continue unabated, thereby producing a much greater repair problem once the true corrosion problem is finally realized.

3. Pipe Thread Leaks

Every pipe thread is an inherent point of weakness, with approximately 50% of the pipe wall cut away. Often, a thread leak is the very first sign of a corrosion problem and will prompt further investigation. Left to continue unaddressed, however, total pipe separation often occurs to produce devastating water-related damages.

While the condition of large piping mains is normally the greatest concern to a building or plant manager, it is the threaded pipe that typically causes the greatest damage.

A high pitting condition will cause failures at random areas of the threads, allowing water to pass through, even though sufficient pipe wall remains to prevent a larger failure. For small leaks where the rate of evaporation exceeds water loss, dissolved iron oxide and other deposits accumulate at the threads to suggest a corrosion problem originating at its outside surface. In reality, however, it is an internal corrosion problem.

For more uniform but high corrosion activity, a more dangerous condition exists at the threads since the pipe wall is reduced more evenly and does not provide the telltale leak indication of a problem. For all forms of thread leaks, the potential always exists to suffer a total thread failure.

4. Galvanic Induced Failure

Galvanic corrosion can occur when different metals are joined together, and is greatly dependent on already existing corrosion conditions and the piping system involved. It is more common in open condenser water and process water systems than in chill water or fire protection systems, for example. It commonly occurs between a carbon steel pipe joined to a brass valve, with the most serious examples found at galvanized steel to brass valve connections. 

A bluish-green deposit at the valve and lack of leakage at its opposite steel-to-steel connection provides confirmation that a galvanic condition exists. It is most prevalent where corrosion activity is already high, and can produce widespread failures and total pipe separations.

In many cases, a leak at a thread between black steel pipe and a brass valve or copper pipe is automatically assumed to be due to galvanic activity when a much larger and more threatening high corrosion problem is actually the cause. In such cases, pipe replacement with dielectric insulating fittings is a costly misdiagnosis that can lead to years of continued higher corrosion activity and eventual system failure.

Galvanic corrosion takes place when two dissimilar metals are present along with acidic solutions. This type of environment creates a battery that produces electrical current flow between the metals. To keep this from happening, a dielectric fitting is used, as it also serves as an insulator between two metals, putting a stop to electrolysis.

5. Interior Pipe Deposits

Internal rust deposits, commonly termed tuberculation, are an inevitable death sentence for most piping systems. They are the lighter and less dense end product of steel pipe corrosion. Once established by high and uncontrolled corrosion conditions, internal deposits initiate much greater deep pitting.

The highest corrosion loss is more likely at horizontal lines and in low flow or dead end areas where rust and other deposits will settle, but can affect vertical lines and main risers as well. Random areas of high tuberculation are actually the result of a high pitting or cell corrosion condition directly beneath it, with the volume or height of the rust deposit directly proportionate to the depth and volume of pipe wall loss.

6. Insulation Failure

Contrary to manufacturers' claims, standard fiberglass insulation provides an ineffective moisture barrier for cold water pipes. Condensed area humidity then produces a secondary, and typically hidden, corrosion condition at the pipe exterior. Most common at chill water and dual temperature systems, external corrosion losses will well exceed internal corrosion rates by up to 10 times or more.

Over decades and hidden from view, insulation failure can destroy entire piping systems. In most examples where the insulated pipe is not hidden from view, an insulation failure problem is very easy to recognize.

Missing, damaged, walked on and broken insulation defines a likely problem worth investigating. Water damage, dripping pipe, discoloration or crystallization of the outer insulation surface are further signs suggesting a potential problem. Aluminum and vinyl outer jacketing provides little resistance to moisture migration, but does shield the often telltale discoloration of the below insulation from view. 

In addition, vinyl jacketing often holds the water condensed at the cold pipe surface, producing a much greater threat of exterior pipe corrosion.

The threat of insulation failure is greatest in smaller diamet