Deteriorating Pipe Quality

In contrast to the high quality of pipe manufactured 50 years ago, we find few new properties unable to control corrosion to below 5 MPY today without expending extraordinary cost, supplemental filtration, close monitoring, and added physical effort.

Chemical treatment programs costing $8,000 only 15 years ago now reach almost 8 times that expense.  Fully automatic chemical feed and bleed systems are no longer a convenience, but mandatory.  Yet, ultrasonic and metallurgical testing at newer installations typically reveal corrosion rates in the 3 – 5 MPY range, with some examples exceeding 15 to 20 MPY.  Such high corrosion rates are even found in examples where the chemical water treatment has been extremely well maintained.

We have either directly seen or have been advised of condenser water or process piping systems which have been entirely replaced after only 10 years of service or less, and have found 6 year old large diameter 8 in. and 12 in. main risers salvaged throughout their facilities using emergency pipe clamps.  In cases where we have investigated building properties having both new carbon steel and older wrought iron pipe, we have consistently provided remaining service life estimates of 100 years or more for the wrought iron, as opposed to a few decades or less for the newly installed carbon steel.

The use of more expensive copper in smaller diameter distribution HVAC piping and process loops has become the standard practice today in the effort to avoid the damaging effects of corrosion against carbon steel.  Larger diameter 8 in. and 12 in. condenser water piping systems running the entire height of large commercial office buildings have been entirely replaced using extra heavy copper and even 304 or 314 stainless steel – such extraordinary expense solely in the effort to avoid the destructive effects of corrosion rarely seen decades earlier.  High wall loss at new copper pipe, historically considered to be almost corrosion free, is no longer unusual.

• New Pipe Provides Generally Less Service Life

While low-cost foreign pipe produced from Japan, Korea, Mexico, South America, and Eastern Europe has traditionally shown the greatest susceptibility to corrosion, we have not found recently produced American carbon steel pipe products of significantly higher quality in terms of corrosion resistance.  Aside from the obvious net effects of stringent U.S. environmental controls and government over-regulation, as well as the competition of low-cost foreign steel, we have not been able to establish, nor has any expert been able to adequately explain the obvious decline in American pipe products in terms of corrosion vulnerability to the same product manufactured 50 years ago.

Highly suspected as a reason for its higher susceptibility to corrosion is the fact that currently produced steel is in its fourth to fifth generation of being recycled.  Other changing factors acting against steel pipe produced today obviously exist.

For those many reasons, CorrView International strongly recommends that higher corrosion rates should be anticipated regardless of any corrosion control measures planned or implemented.  Simultaneous to higher corrosion is a higher volume of rust deposits, and therefore, effective water filtration is no longer an option – but an absolute necessity today.  It should be noted that standardized corrosivity tests, laboratory methods capable of measuring the susceptibility of a metal to a typical corrosive environment and rating that metal according to an established numerical scale, are available, and offer an excellent prediction or warning to the potential for future corrosion problems.

Hard documentation to the higher corrosion level suffered by newer pipe was provided in a recent series of investigations of approximately 20 U.S. government facilities throughout the United States identically constructed at the same time, and all having the same mechanical and piping expansions.  Constructed in 1960 and having new additions roughly each decade produced a revealing graph of corrosion activity when plotted against its year of installation.

In short, testing at chill water, condenser water, and hot water heating pipe all showed a near 10 times increase in the rate of corrosion for pipe installed in 2005 as opposed to that installed in 1960.  Contrary to the expectation of facility engineers concerned to the condition of the older pipe, thereby the reason for the investigation, ultrasonic testing revealed the older pipe in substantially better condition.  Far greater corrosion problems were found at the pipe installed since 2000 for every facility evaluated.

This condition is clearly shown in the below summary graph with the X axis representing the installation date and Y axis representing corrosion rate.  For each piping service, the older pipe from 1960 is shown at left, and the more recently installed pipe is shown at right.  More information on this subject is available Here.

Corrosion Rate vs. Pipe Age

• Schedule 40 (Light)
  

A growing difficulty in producing accurate piping assessment reports is caused by the widespread manufacturing of pipe well undersized its stated ASTM wall thickness specification.  This is a very common finding for any newer property constructed over the past 15-20 years, and extends to almost all pipe manufactured today – carbon steel, stainless steel, copper, galvanized steel, cast iron, and ductile iron.  Not only is undersized pipe beyond the control of those specifying, designing, and installing new piping systems, the issue is almost completely unknown.  To some within the our industry, however, it is quietly ignored and unspoken.

Like the increasingly shrinking bag of potato chips or box of snacks, pipe manufacturers similarly provide less product for the money.  Unlike less product in the package, now labeled 14 oz. rather than 16 oz, steel pipe is still believed to exist as it is stamped.  Pipe stamps, however, whether ASTM, FM, or UL, only refer to the official wall thickness specification for that pipe and not its actual wall thickness.  In the example at left, an ASTM pipe stamp of 6.625 in. x 0.280 in. only means that this new uninstalled pipe should have a wall thickness of 0.280 in.  But in reality, the pipe wall is manufactured at 0.244 in. – actually below its 12.5% minimum ASTM allowance.

Such findings of undersized pipe in virtually all ultrasonic investigations of newer properties totally exceed the possibility of their being random events.  First observed at examples of foreign produced pipe going back 20 years ago, it would seem that U.S. manufacturers soon followed.

• Material Selection

For older pre-1970’s building properties or plant operations, it is unlikely to find anything but schedule 80 or extra heavy black pipe in use for cooling water, steam, or steam condensate service. However, today, schedule 40 is the standard specified.  Contrasted to a 0.322 in. wall thickness for an 8 in. section of schedule 40 pipe, schedule 80 provides a significantly greater 0.500 in. of available steel.  Contrasting any larger diameter standard grade pipe of 0.375 in., extra heavy pipe offers 0.500 in. of wall thickness.

With internal operating pressures rarely a deciding factor to pipe selection within the commercial building and process cooling market, the previous use of heavier materials, we believe, has been more intended to counteract the known effects of corrosion activity and thereby provide longer service life.

It is important to realize that decades ago, design engineering for piping systems assumed a reasonable and readily achieved 1 MPY corrosion rate over an intended life expectancy of about 65 years for the typical building property – therefore a theoretical 65 mil corrosion rate or “corrosion factor” was typically applied in piping calculations for open condenser water or process cooling applications.  In other words, consulting and design engineers estimated a total loss of only 65 mils or 0.065 in. of pipe over the assumed lifetime of the property.  Any additional pipe wall thickness exceeding the corrosion factor and beyond that needed to contain the internal pressure and stresses was simply extra insurance against corrosion losses and future operating problems.

Today, it is not unusual to measure the same loss of 65 mils after only 5 to 10 years of service, and sometimes in as little as two years.  But while corrosion activity has obviously increased, the response to this greater loss of pipe has not been factored into the design and planning of modern piping systems – leaving very little if any tolerance for a system wide corrosion rate exceeding a few mils per year.  In fact for many piping systems such as fire sprinkler, substantially thinner piping materials are now installed – schedule 10 and schedule 7.

CorrView International has found many building properties constructed in the 1970’s and before having clearly benefited from such engineering decisions – with the heavier schedule 80 pipe wearing over those many decades at low to moderate corrosion rate to approximately schedule 40 today.  Some older properties, due to the original use of better quality schedule 80 steel, actually have heavier and longer lasting pipe than their newly constructed neighbors.  Where new additions have been made to older properties, it is not unusual to measure much greater wall thickness for the older pipe installed decades earlier. It is an amazing paradox we have well documented in endless ultrasonic testing investigations.  More information on this subject is available Here.

• Added Threat For Threaded Pipe

This change in engineering design toward using thinner schedule 40 pipe, and sometimes schedule 20 and schedule 10, is far more obvious and threatening for smaller diameter threaded applications – where the additional loss of metal during the threading process often reduces the life expectancy of open condenser water or process water piping to a decade or less.  Threading typically reduces the available wall thickness by approximately 50% – leaving a 0.154 in. thick piece of 2 in. schedule 40 pipe, minus its thread cut of 0.072 in., with a true available and working wall thickness of only 0.082 in. beginning day one of service.

For piping systems having a typical 5 MPY corrosion rate, total penetration of the threads will occur within 16 years of installation – guaranteed.  In reality, failure usually occurs years earlier. In fact, the use of schedule 40 or standard grade pipe in threaded open water condenser applications does not meet minimum acceptable engineering guidelines for new piping systems, and will typically provide only 15-20 years of service life under good to moderate corrosion conditions.  The failure of a threaded schedule 40 piping system in under 5 years is not unusual, based upon our experience.

A growing concern is the recent increase in the use of grooved and clamped constructed schedule 10 pipe in fire sprinkler service. While providing adequate wall thickness initially, schedule 10 pipe has approximately half of the thickness of schedule 40, leaving very little tolerance for corrosion to occur.  Where fire pipe is filled and left stagnant over extended time, a small amount of corrosion takes place, oxygen is depleted, and the corrosion process virtually stops.  However, where the fire system is frequently drained, or where service extensions, leaks, or repairs bring in fresh water, corrosion rates can reach the level of open water systems, and premature failure is inevitable.

Clamped schedule 10 pipe is seeing greater use in open condenser water piping systems as well – producing disastrous results in even less time.

CorrView International, LLC overwhelmingly recommends using heavier schedule 80 steel pipe in all small diameter applications calling for threaded joints.  We also recommend using no thinner than schedule 40 pipe for fire sprinkler or open water condenser systems – whether using threaded, welded, or Victaulic or grooved clamped construction.  More information on this subject is available Here.

• Chemical Water Treatment

For many decades, building and plant engineers relied solely upon the use of chromate based chemical additives to provide the required corrosion protection of steel piping systems.  With even the most inferior application methods, often nothing more than an unmeasured scoop of chromate powder dumped into the cooling tower sump at irregular intervals, corrosion rates could often be maintained at or below 1 MPY. Biological fouling was a rarely encountered problem due to chromate’s inherent toxicity.  Such trouble free operation ended, however, in the mid-1980’s – with the prohibition of all hexavalent chromate use in open water circulating systems in the United States.

Today, molybdate, phosphate, and other U.S. EPA approved chemical inhibitors rarely equal the effectiveness of past chromate treatments. Molybdate, which was considered less effective than its predecessor chromate, is now being replaced by less effective phosphates due to excessive molybdate costs.  Though offering impressive corrosion suppression in bench test or laboratory settings, non-chromate programs rarely provide similar results under real world conditions.  They are suggested by some authorities as being substantially ineffective in stagnant, low flow, or dead ended piping areas.  During our years of ultrasonic pipe testing, we have identified numerous examples where the highest corrosion rates have been found exclusively at those areas having the lowest flows.  We also attribute much of such higher corrosion rates to rust settlement and secondary corrosion effects.

Non-chromate treatments offer no microbiological or fungal control – thereby placing increased emphasis on the use of alternating biocide chemicals. Unfortunately, biocides themselves have had their effective half-life reduced to approximately 6 hours by U.S. federal and state environmental authorities.  The result – a legal limit of the amount of biocide one can apply over a given period of time, as well as a legal limitation over its strength, effectiveness, and the time it will remain active.

And yet, microbiological activity has been found to play an increasing role in metal corrosion – MIC being the most serious and potentially destructive piping threat known.  The alternative, using oxidizing biocides such as chlorine, bromine and ozone, all offer excellent microbiological control at the trade off of greatly increased corrosion and pitting.  The common overuse of oxidizing agents such as chlorine and bromine on a weekly or daily basis have been known to produce severe pitting of steel and copper pipe, and to quickly remove the galvanizing coating from cooling tower pan surfaces.

• Combined – A Significantly Greater Threat

Together, the combination of all the above named factors has placed a higher priority on corrosion control which did not exist 25-30 years ago, and which has raised the issue of chemical treatment, and the monitoring over its effectiveness to new levels of importance within those involved in building and plant engineering, maintenance, and operations.

Virtually all advanced piping failures we have seen have been traced back to an ineffective or lacking water treatment program at some point in the building’s history – most notably due to poor initial clean out and start-up procedures.  Quite clearly, the first six months of operation are critical, and can mean the difference between long and reliable operation, or substantially fewer years of corrosion inflicted problems. To the inherent limitations of the chemicals must be added the experience and reputation of the water treatment professional.  A lack of knowledge, experience, and professionalism, or a primary interest for profits can be equally as damaging to a piping system as a lack of chemical protection entirely.

A less reputable water treatment company may be discovered and replaced, but the effects of even six months of sub-standard service can initiate a lifetime of corrosion headaches for an office building or plant operation.  A further limitation may also be the budget constraints of the property or plant itself, or the need to meet a contract limit established by a previous water treatment vendor.  The failure to timely recognize and effectively address a corrosion problem will place even further demand upon any future chemical treatment contractor and available control products.

For many of the worst corrosion caused failures we have investigated, total reliance on the information provided by corrosion coupons kept even the most obvious clues to a corrosion problem, such as thread leaks and rust deposits, from being further investigated.  Although capable of providing some information relating to whether corrosion activity may be increasing or decreasing, corrosion coupons results have nothing to do with the wall loss occurring at the pipe itself, and therefore are virtually worthless as a corrosion measurement and monitoring tool.

Ultimately, some building property or plant operator is faced with not only the difficult task of correcting or replacing a piping system, but perhaps a responsibility for the actions or inaction of those years prior as well.  Accurate and reliable corrosion monitoring is therefore critically important.

© Copyright 2023 – William P. Duncan, CorrView International, LLC