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Eliminate Corrosion Problems at Pipe Supports with I-Rod®

Corrosion at pipe supports is one of the leading causes of process piping failures, which can have potentially catastrophic results. Beam supports, saddle supports and pipe shoes create crevices where water is trapped and held in constant contact with the pipe surface. Under these conditions, crevice corrosion quickly undercuts the paint coating and causes rapid wall loss.

Crevice Corrosion

Actual times to failure will vary from case to case, but the progression of events always follows the same basic sequence:

 

1. A crevice is created which does not allow water to escape or evaporate. Water is trapped in close proximity to the pipe for long periods of time.

2. The paint system on the pipe is now placed in continuous immersion service rather than the intermittent immersion service anticipated by the paint specifications. As a result, the paint system softens and fails prematurely. This begins with a pinhole defect.

3. The steel is now directly exposed to moisture and the oxidation (corrosion) process begins, consuming oxygen from the water. Crevice corrosion works quickly as long as moisture is trapped. It is vital for the life of the pipe to ensure that it stays as dry as possible.

Metal to Metal Contact

A major misconception within the industry is that the primary corrosion reaction between pipe and support is galvanic, driven by metal-to-metal contact. This is incorrect. Though two dissimilar metals connected within an electrolyte will create a galvanic cell, the primary corrosion mechanism at work is actually crevice corrosion, which creates a localized cell on the pipe surface and accelerates oxidation much more quickly.

Inspection Difficulties

Most “standard” piping designs do very little to prevent corrosion failure at the support, and some solutions even make it impossible to inspect the pipe surface. Inspection is the only way to verify that a crevice has not been created.

Refineries have been using contoured pads made from FRP (Fiberglass) or steel for many years. The purpose of these pads is to eliminate wear to the pipe at supports, which move due to thermal cycling. These pads are not an effective guard against crevice corrosion; adhesion cannot be guaranteed and the pads make inspection for corrosion impossible.

If adhesion is lost between pad and pipe, a large crevice will form and trap water inside the gap. An aggressive corrosion cell will begin to corrode a large area of the pipe beneath the pad. Without inspection, the problem will likely go undiagnosed until failure. Moisture penetration is virtually unavoidable in most instances and the resulting failure can be dramatic.

The Solution

Deepwater developed the I-Rod brand of pipe supports specifically to combat crevice corrosion and ensure a long, safe life for pipelines by eliminating the crevice between the pipe and the support. I-Rod is a durable extruded thermoplastic cut into a half-round rod. It is the key component in all of Deepwater’s I-Rod pipe supports.

The way that I-Rod works is simple:

1. The half-round shape minimizes contact between the pipe and the support, eliminating the crevice.

2. It also provides an electrically isolated stand-off between the pipe and the supporting beam or saddle clamp. This allows for easy maintenance and inspection while preventing galvanic corrosion between dissimilar metals (the pipe and support).

3. 3. I-Rod has excellent compressive strength and a very low friction coefficient, making it ideal as a beam dressing. Pipe damage during new construction is reduced when I-Rod is used to assist pipe fitting.

The I-Rod by Deepwater is just one of the many solutions available from Innocorr Offshore Sdn Bhd. To find out how Innocorr can extend your assets’ lifespan, consult with their specialists directly at booth 4A001, Coatings & Corrosion Asia, 17 – 19 May 2016.

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