《Life Cycle Costs of Industrial Protective Coatings》
Industrial Galvanizers Corporation (IGC) operates nine galvanizing plants around Australia, ranging in size from large structural galvanizing facilities to specialised small plants designed to process small parts.
The Australian Galvanizing Division has galvanized in excess of 2.5 million tonnes of steel products in Australia since its first plant was commissioned in 1965 and is recognized for its ability to handle complex and difficult projects, as well as routine contracts.
This experience has been collated in the Specifiers Design Manual, to assist those involved in the design of steel products and projects to better understanding the galvanizing process and allow the most durable and cost-effective solutions to be delivered to these products and projects.
The concept of life cycle costing is not a new one. Standards Australian produced its first AS/ NZS Standard in 1999 ; AS/NZS 4536 – Life cycle costing – An application guide.
In any life-cycle costing assessment, the initial cost of the coating is an important component in doing any long-term cost analysis, as is the need to determine the likely maintenance free life of the coating and the future costs of maintenance.
生命周期成本计算并不是一个新概念。澳大利亚标准协会于1999年首次制定了AS/ NZS标准;AS/NZS 4536 -生命周期成本计算应用指南。在任何生命周期成本评估中，涂层的初始成本是进行任何长期成本分析的一个重要组成部分，同样需要确定涂层可能的免维护寿命和未来的维护成本。
A bit of History
Protective coating costs on most projects are a relatively small component of the total project cost; typically less than 2%. On a major steel project containing, say, 1000 tonnes of structural steel, the cost of a basic protective coating system may be in the order of $500/tonne, a high performance coating system may be $1000/tonne, and a special super-durable specification may cost $1500/tonne.
This equates to an additional project cost of $500,000 – $1,500,000. If a project accountant applied a net present value analysis to this in the 1980’s, when interest rates exceeded 15% and company taxation was well over 40%, the option of using the cheaper coating and expensing accelerated maintenance costs would seem a sound financial decision.
However, in the 21st Century, company tax is only 30% and interest rates are lower, so the Tax Office no longer subsidises maintenance costs to the same degree. In addition, expensed maintenance costs hit the balance sheet at a level that exceeds any interest benefits from the original saving.
Also, the labour costs of the 1980’s did not include the on-costs of superannuation, higher workers compensation and other statutory obligations for employers. Nor were the WH&S and environmental obligations anything like they are today.
It is thus very difficult to foretell the distant future for the purposes of life-cycle costing for protective coatings, and conditions in 2035 will have changed as much in that 25-year cycle as they did between 1950, 1975 and 2000.
The other reality faced by asset owners, particularly of infrastructure assets, is that their service life is often far longer that originally anticipated. Many power distribution and transport structures are now well over 50 years old and are subject to numerous maintenance cycles to maintain their functionality.
The other issue with maintenance coatings is that they add very little value to a business. They make no contribution to efficiency or productivity.
For this reason, the selection of an appropriate protective coating system for steel, be it paint, galvanizing, or a combination of both should be based on the performance of the coating over time rather than its initial cost.
Factors in the Cost of a Coating
Australian Standards such as AS/NZS 2312:2002 – Guide to the protection of iron and steel against atmospheric corrosion contains comprehensive guidelines related to coating selection versus environmental condition to provide an estimated service life for a range of coating systems.
The choice between materials of construction will usually be a `steel versus concrete decision’, with a proportion of projects being a composite of both.
The decision may be based on familiarity of a designer of working with one material or another, the form of the structure, its location and most importantly, its installed cost.
While the protective coating costs are a relatively small component of the total projects cost, they can be a significant proportion of the structural steel cost. In addition, steel simply cannot be used (with a few exceptions) without protective coatings and these coatings will have a defined life that will determine future maintenance costs.
While steel and fabrication costs are volatile, benchmark costs obtained in mid-2012 indicate that the cost components are approximately as follows for standard medium structural steel:
Medium structural steel cost: $1200/t
Fabrication cost: $3000 – $5000/t
制造成本:3000 – 5000美元/吨
Coating Costs for new Steelwork
The cost of coating new steelwork is made up of a number of factors. These are:
The type of steel – size, shape, section.钢的型号-尺寸、形状、截面。
The quantity of steel钢材数量
The location of the project with respect to the coating provider, the fabricator and the site.关于涂料供应商、制造商和现场的项目位置。
The regional cost of labour地区劳动力成本
The material cost (paint components/zinc/ chemicals)材料成本(油漆成分/锌/化学品)
The cost of surface preparation (abrasive blasting/chemical/mechanical)表面处理成本(喷砂/化学/机械)
The cost of application – number of coats, plant capability, processing time应用成本-涂层数量，工厂能力，处理时间
Logistic costs – inspection, loading, transport, erection物流成本-检验，装载，运输，安装
Post erection costs – remediation of handling damage, on-site completion安装后费用-处理损坏的补救，现场完成。
For applied coatings (paint, metallising) the surface area of the steelwork and the complexity of the fabrication will be the most significant factors influencing the cost. Logically, thin steel sections with high surface area per tonne will absorb more labour and materials than heavy structural sections.
For example, a 3 mm thick steel section has a surface area per tonne of over 80 m2, while a 10 mm section has a surface area of 25 m2 per tonne.
For process-applied coatings (hot dip and continuous galvanizing, powder coating), material costs and fixed costs are important, making the profitability of these processes very volume sensitive.
Typical Material Costs
Many of the materials incorporated in coatings are traded as commodities with supply and demand affecting prices above and beyond normal inflationary variations. The following indicative prices are for generic materials used in coating in mid-2008, in commercial quantities
|Red oxide zinc phosphate磷酸锌红||$10.0/litre|
|High build epoxy环氧厚涂||$14.00/litre|
|Urethane – standard grade聚氨酯-标准等级||$12.00/litre|
|Urethane GP3 grade聚氨酯GP3年级||$25+/litre|
|Acrylic – water based丙烯酸-水基||$8.00/litre|
|Acrylic – catalysed对丙烯酸-催化||$12.00/litre|
The true material cost of paint coatings is determined by how much of what is in the can ends up on the steel surface. This is determined by the volume solids in the paint, the applied thickness of the coating and the coating efficiency (over-spray losses).
Low volume solids will result in higher losses due to solvent evaporation. Simple solid structures (beams, tanks) will experience higher coating efficiencies that open structures (pipe work and trusses)
One litre of paint, applied to a wet film thickness of 100 microns will theoretically cover 10 m2 of surface. In practice, the same paint applied to a dry film thickness of 100 microns, to medium structural steel by airless spray will cover approximately 5 m2.
All paint suppliers have product safety data sheets for each of their paints. These documents list technical specifications for the paint, including volume solids, recommendations for wet and dry film thickness requirements and theoretical coverage.
In addition to the paint cost, most solvent-based spray applied coatings require the addition of thinners, (typically around 30% by volume) which becomes a component of the paint material cost.
An important point to note is that the paint cost is a relatively small proportion of the applied system cost. Based on a typical practical coverage rate of $5.00/m2, the cost differential between a basic industrial epoxy or urethane and a high performance urethane or polysiloxane is in the order of $3.00-$4.00/m2.
The most significant single cost in paint coatings is surface preparation. Abrasive blasting is almost mandatory to ensure acceptable performance for industrial paint systems.
Fabricated steelwork is usually abrasive blasted with chilled iron shot, in a chamber that allows recovery and recycling of the blasting media. Abrasive blasting standards are defined in Australian Standard AS 1627.4. Class 2 ½ Blast is most commonly specified for industrial coating, with Class 3 (the highest level) being a requirement for specialised coatings such as zinc metal spray.
Abrasive blasting costs vary regionally, but generally fall in the $15.00 – $20.00/m2 range. Large automated blasting facilities using wheelabrador equipment to process columns, beams and plates can significantly reduce this cost.
喷砂成本因地区而异，但一般在$15.00 – $20.00/m2范围内。大型自动化爆破设施使用轮对爆破设备来处理柱、梁和板可以大大降低成本。
Where galvanized coatings are to be painted, Class 1 or whip blasting is generally specified. This involves using less aggressive media such as garnet or illmentite, at typical cost ranging from $10.00 – $15.00/m2, depending on the complexity of the fabrication.
Chemical preparation (pickling, phosphating) is rarely used as a method of preparing fabricated steel for painting, and is confined to process applied coatings such as powder coating and galvanizing.
Powder coating costs are usually charges on a `window area’ basis rather than surface area, as the area the item takes up on the powder coating line is the main factor in its cost of processing. For standard grades of polyester powder, powder coating costs are typically $15.00 – $20.00/m2, although large quantities of uniform manufactured product that can be loaded to high line efficiencies can be powder coated at lower cost.
粉末涂料的成本通常是按“窗口面积”而不是按表面积计算的，因为产品在粉末涂料生产线上所占的面积是其加工成本的主要因素。对于标准等级的聚酯粉末，粉末涂料的成本通常为$15.00 – $20.00/m2，尽管大量的均匀生产的产品可以装载到高生产线效率，也可以以较低的成本粉末涂料。
With all costs included (labour, overheads, margins) indicative industrial painting costs for commonly specified systems are:
Basic wire brush/Class1 blast and ROZP prime —> $12.00/m2基本钢丝刷/Class1 blast和ROZP prime -> $12.00/m2
Class 2 ½ blast + inorganic zinc primer —> $25.00/m2类2½爆炸+无机富锌底漆- – – > 25.00美元/平方米
Class 2 ½ blast + inorganic zinc primer + epoxy topcoat —> $35.00/m2类2½爆炸+无机富锌底漆+环氧面漆- – – > 35.00美元/平方米
Class 2 ½ blast + inorganic zinc primer + urethane —> $45.00/m2类2½爆炸+无机富锌底漆+聚氨酯- – – > 45.00美元/平方米
NOTE: These are indicative average prices only and will vary regionally and depending on the design of the items being painted.
The parameters governing the cost of galvanized coatings are quite different to those determining paint costs.
Continuously applied galvanized coatings applied to sheet, wire and tube are applied in facilities with high capital and operating cost, with large volumes of steel being able to be processed very efficiently.
For this reason, the galvanized coating cost component of these products is relatively small and driven by the material (zinc) cost. In addition, these technologies apply relatively thin zinc coatings – usually less than 30 microns per side for a material cost of about $0.75/m2 of surface.
Hot dip galvanized coatings applied to fabricated steelwork are priced on the basis of the tonnage that can be processed through the galvanizing bath. Surface area is thus not as significant in galvanizing costs. Thin sections that can be loaded into galvanizing jigs at high loading density will attract a relatively low galvanizing cost, while 3-D structural fabrications containing heavy universal sections may be more costly to process.
Hot dip galvanized coatings are almost always costed on a $./tonne basis. Typical galvanizing costs per tonne will range from $650/tonne for heavy, simple elements such as columns and beams in large project quantities, to $1500/tonne for light fabrications. Items requiring double-end dipping will usually attract a premium cost and small one-off fabrications (boat trailers, wrought iron, anchors etc) for non-account customers will be charged around $2000-$2500/tonne.
The cost per square metre for hot dip galvanizing reduces quite significantly as sections become thinner. The following examples illustrate this:
Medium structural steel – 10 mm average thickness
Galvanizing cost: $700/tonne
Surface area per tonne: 25 m2/tonne
成本/ m2: 28美元/平方米
Light fabrications – 3 mm average section thickness
Galvanizing cost $1500/tonne
Surface area per tonne: 85 m2/tonne
成本/ m2: 18.00美元/平方米
A fringe benefit of hot dip galvanizing, because it is an immersion process, is that all internal surfaces of hollow sections are coated uniformly. This may be an advantage or disadvantage, as the external surface area of a hollow section is only half that of an open section of the same section thickness.
Another fringe benefit of hot dip galvanizing compared to both paint coatings and continuously galvanized coatings is that the applied coating thickness almost always in excess of Australian Standard requirements.
This is a bonus for the customer, as additional zinc pick-up on steelwork cannot be accurately predicted by the galvanizer, as it is influenced by the surface condition, section thickness and chemistry of the steel. It can add $50-$100/tonne to the galvanizer’s material costs, with the added bonus for the customer of the extra zinc adding proportionately to the service life of the coating.
The Realties of Future Maintenance
Where maintenance coating is required on an infrastructure or industrial project, the real cost experienced in 2008 would not have been even considered 25 year ago.
The major cost factors impacting on maintenance costs include:
It is worth looking at each of these factors in more detail.
It is now mandatory in most jurisdictions in Australia to use scaffolding systems when working at heights. Ladders and trestles are no longer acceptable for commercial coating contractors.
The cost of erecting, hiring and dismantling scaffolding is a major component of any maintenance coating operation. Since the introduction of more stringent safety requirements on residential building sites, few houses are now built that do not require scaffolding to be erected during their construction. While this is not directly connected to the life-cycle costing of industrial coatings, it is worth noting that the value of the residential scaffolding market in Australia now exceeds $250 million annually.
On industrial projects, much larger scaffolding systems may be required to provide the needed access for maintenance.
In assessing the likely maintenance costs, access factors can be applied to life cycle costing models to more accurately estimate costs on a specific structure.
It is possible to classify structures for assessing access issues. The following is an example:
Level 1 – Simple structure to 15 m. Maintenance able to continue while structure is operational. Easy access for scaffolding or lifts.一级-简单结构，高度15米。结构运行时可以继续进行维护。方便脚手架或升降机。
Level 2 – Simple structure 15-30 m. Greater scaffolding requirements. Maintenance able to be done while structure operational.二级-简单结构，高15-30米。更大的脚手架要求。能够在结构运行时进行维护。
Level 3 – Simple structure over 30 m. Specialised external access required. Operating requirements of other plant and equipment must be considered.三级-简单结构，高度30米以上。需要特殊的外部访问。必须考虑其他工厂和设备的操作要求。
Level 4 – Complex structure to 15 m. Internal and external access required. Operating requirements of other plant and equipment must be considered.四级-复杂结构，高度15米。需要内部和外部访问。必须考虑其他工厂和设备的操作要求。
Level 5 – Complex structure 15 – 30 m. Internal and external access required. Staging at each level may be required. Operating requirements of other plant and equipment must be considered.5级-复杂结构，15 – 30米。需要内部和外部访问。可能需要在每个级别上进行分段。必须考虑其他工厂和设备的操作要求。
Level 6 – Complex structure over 30 m. Staged internal and specialised external access required. Operating requirements of other plant and equipment must be considered.6级- 30米以上的复杂结构。需要阶段性的内部和特殊的外部访问。必须考虑其他工厂和设备的操作要求。
Like access, containment costs will vary with the complexity of the requirements for containment. As with access, models can be developed to classify containment levels and factor in the costs of containment for a specific containment requirement.
An example of classification of containment factors is as follows:
None – No recovery of residues or paint.没有-没有回收残留物或油漆。
Level 4 (Minimum) – For abrasive blast cleaning only – air penetrable walls, flexible framing, open entryways and natural air flow.4级(最低)-仅用于喷砂清理-可穿透空气的墙壁、柔性框架、敞开的入口和自然气流。
Level 3 (Moderate) – For abrasive blast cleaning – air penetrable walls, rigid or flexible framing, partially sealed entryways and joints, exhaust air filtration.3级(中等)-用于磨料喷砂清理-空气可穿透的墙壁，刚性或柔性框架，部分密封的入口和接头，排气过滤。
Level 2 (High) – For abrasive blast cleaning – air impenetrable walls rigid or flexible framing, fully sealed joints, airlock entryways, negative air flows and exhaust air filtration.2级(高)-用于磨料喷砂清理-空气不透壁，刚性或柔性框架，全密封接头，气闸入口，负气流和排气过滤。
A good example of high-level containment is the maintenance painting program undertaken on under-road steelwork on the Sydney Harbour Bridge, which also incorporates very complex staging and access systems.
Where lead based paints are concerned, additional environmental management systems may be required to monitor local soil and water system during the remediation activities.
3. WH&S Management职业健康
Worker safety is now the first priority in any business and where heights are involved, stringent requirements for personal safety equipment are mandatory. Industrial manslaughter laws apply in many Australian States, and while managers should not need the threat of such legislation to care for the welfare of their workers, it is an indication that the most stringent risk assessments must be applied to any hazardous activity.
Certified safety equipment is mandatory when working at height, and approved safety harnessing and attachment systems have to be provided by contractors. Other Workcover regulations related to working in enclosed spaces places further onus on employers to ensure that no cost-cutting shortcuts are taken in the provision of maintenance coating services.
Each of the above factors will have an impact on productivity. With new steelwork, labour costs represent about 75-80% of the coating cost. For on-site maintenance, the labour cost component is far greater and for this reason material costs (paint costs) are less significant and more expensive surface tolerant paints will have little impact on the overall costs of a maintenance project, and represent better value given the expectation of higher levels of performance.
Surface preparation is the most labour-intensive part of the process. Surfaces may be contaminated with soluble salts so may require water washing/ blasting prior to mechanical removal of the rusted surface or failed paint coating.
As a guide, the cost per square metre for maintenance coating a rusted steel structure may be 5-10 times the cost of applying an equivalent coating to new steelwork.
Regardless of the protective coating used, there is a strong case, particularly in the present environment of low interest rates and decreasing company taxes, to use the longest life coatings available commensurate with the design life of the asset.
This may mean more stringent inspection with applied coatings, the use of QA certified applicators or the insistence in a coating performance guarantee from the supplier to better manage the risk and avoid the inevitable and more costly than expected future maintenance costs.