The Treatment of Durability in CES EduPack A white paper

It is one of the more difficult attributes to characterize, quantify and use for selection because • It is a function not just of the material but of the environment in which it operates

The Treatment of Durability in CES EduPack

A white paper Mike Ashby, Cambridge UK

March 2009

1 Introduction

Durability is a key material attribute, one central to the safety and economy of products It is one of the more difficult attributes to characterize, quantify and use for selection because

• It is a function not just of the material but of the environment in which it operates

• There are many mechanisms, some general, some peculiar to particular materials and environments

• Material combinations (as in galvanic corrosion) and configuration (as in crevice corrosion) play a role Figure 1 shows some of the considerations involved The central players are Materials and Environments But the fact that a given material is resistant to a given environment is not enough – there are many other considerations, some of them listed on the Figure First there is the Industrial sector in which the material is to

be used: some are limited to material lightweight materials, some to non-flammable materials, some to bio-compatible materials Second, there are many Mechanisms of attack, some general, some appearing only under special conditions Third, there are Protection methods, some generally applicable (like painting), some specific

to particular combinations of material and environment (such as inhibitors) And finally there are issues of Design, often specific to a given industry Thus there are preferred material choices for use in a given

environment – those that, through experience, best meet both the primary constraint of resisting attack and the secondary constraints of stiffness, strength, cost, and the like

Figure 1 CES EduPack records deal explicitly with materials and environments The other

information is captured, as far as possible, in Notes attached to the each environment field, in

the way shown in Figure 3

This White Paper describes the way in which Durability is treated in CES EduPack Section 2 lists the environments Section 3 describes the data organisation and information provision in CES EduPack Section 4 illustrates how the database is used Appendix A reviews currently available software for durability selection Appendix B gives examples of the data

2 The materials and the environments

The material set is that of the CES EduPack Level 2 database It contains records for 97 materials,

organized under the headings shown in Table 1 The records contain a description and image of the material, data for general, mechanical, thermal and electrical properties, properties relating to the impact of their use on the natural environment, design guide-lines, technical notes, typical uses and trade names

Table 1 The material families and classes

Non ferrous

Thermoplastics Thermosets

Fired clay Glasses Minerals and stone Technical ceramics

Foams Natural materials

Table 2 lists the 53 environments – it is a subset of a longer list of the kind found in the Chemical

Resistance tables of CES EduPack or the compilation by Schweitzer (1995) or that used by NACE, expanded by the addition of Built Environments (to include use in Architecture) and Thermal Environments (giving a way to select materials for use at high temperatures)

Table 2 The 53 environments

Alcohols, aldehydes, keytones Acetaldehyde

Acetone Ethyl alcohol (ethanol) Ethylene glycol Formaldehyde (40%) Glycerol

Methyl alcohol (methanol)

Halogens and gases Chlorine gas (dry) Fluorine (gas) Oxygen (gas) Sulfur dioxide, SO 2

Built environments Industrial atmosphere Marine atmosphere Rural atmosphere

UV radiation (sunlight) Flammability

Thermal environments Cryogenic (down to -273 C) Tolerance to 150 C Tolerance to 250 C Tolerance to 450 C Tolerance to 850 C Tolerance above 850 C

Chemical environments

Water & Aqueous Solutions

Water (fresh)

Water (salt)

Soils, acidic (peat)

Soils, alkaline (clay)

Wine

Acids

Acetic acid (10%)

Acetic acid (glacial)

Citric acid (10%)

Hydrochloric acid (10%)

Hydrochloric acid (36%)

Hydrofluoric acid (40%)

Nitric acid (10%)

Nitric acid (70%)

Phosphoric acid (10%)

Phosphoric acid (85%)

Sulfuric acid (10%)

Sulfuric acid (70%)

Alkalis

Sodium hydroxide (10%)

Sodium hydroxide (60%)

Fuels, oils and solvents

Amyl acetate

Carbon tetrachloride

Chloroform

Crude oil

Diesel oil

Lubricating oil

Paraffin oil (kerosene)

Petroleum (gasoline)

Silicone fluids

Toluene

Turpentine

Vegetable oils

White spirit

3 The way Durability is treated in CES EduPack

When CES EduPack is opened in Browse or Select mode, the user has the ability to choose a selection template One of the options under EduPack Level 2 is Materials with Durability, as shown in Figure 2 This presents, under the heading Durability, the 53 environments, grouped under eight headings: Water & Aqueous solutions, Acids, Alkalis etc as listed in Table 2 Each material is given a ranking in each environment, using a

4 point scale: Excellent (A), Satisfactory (B), Doubtful (C), Unsatisfactory (D) Table B3 of Appendix B lists

a subset (about one third of the total) of the materials and environments with their ranking on this scale

Materials to resist a given environment are best selected using a Limit stage Figure 3 shows part the display for environments under the heading of Acids Ticking the box for Excellent, or those for Excellent and for Satisfactory, for a chosen environment, limits the selection to materials that carry these rankings

This, however, may not always be the best way to select materials for durability because there are other issues involved Durability can be achieved by choosing a material that does not corrode or react in a given environment But it can also be achieved by protection with corrosion inhibitors, by coatings, or – when corrosion is uniform rather than localised – simply by providing sufficient section that the loss over the design life does not compromise the integrity of the component The preferred choice of material or coating may, for economic reasons, not be the one most resistant to attack, but a cheaper one that is still satisfactory in its performance This information, and more, is contained in sets of Notes, accessed by double clicking on the group name (e.g on “Acids”) or on the name of the environment (e.g “Hydrochloric acid”) Figure 3 illustrates the two sorts of notes that are accessed by double clicking on the headings and environment names These are described next

File Edit View Select Tools…

File Edit View Select Tools…

MaterialUniverse

Edu Level 2

Edu Level 2

Table:

Subset:

MaterialUniverse

Edu Level 2

Edu Level 2

Table:

Subset:

<All records>

Edu Level 1

Edu Level 2

Edu Level 2 with durability

Edu Level 2 with eco props

Edu Level 2……

<All records>

Edu Level 1

Edu Level 2

Edu Level 2 with durability

Edu Level 2 with eco props

Edu Level 2……

Figure 2 Opening the CES EduPack data base with durability attributes

Science notes The headings (Water and Aqueous solutions, Acids, Alkalis etc) are linked to Science notes that outline the underlying science – the chemical reactions, the rate of attack etc – associated with the subject of the heading Thus “Acids” in Figure 3 is linked to pages of Science notes about the nature of acid attack They parallel the Science notes attached to the mechanical, thermal, electrical and optical properties in the database Environment notes The environments (Acetic acid, Citric acid, Hydrochloric acid etc) are linked to Notes of a different kind Their purpose is to capture some of the peripheral information suggested by Figure 1 Each Environmental note is headed by the environment name and chemical formula The first item in the Note (“where found”) lists the circumstances under which this environment in encountered Table B1 of Appendix B lists some of these The second lists the industrial sectors in which it is commonly encountered, drawn from the list in Table 3 The third describes the problems caused by a given environment, particularly the classes of material that are most vulnerable to it

This introductory information is followed by a list of the preferred materials and coatings used when the design requires resistance to that environment (Table B4 of Appendix B lists a subset) The purpose is to direct the user to the Metals, Polymers and Ceramics and Glasses most commonly used to contain, transport or process the environment The choice is influenced both by resistance to attack and by the economics of its use, and for that reason is not always the most obvious one Materials for which records can be found in CES EduPack

Figure 3 The way information on

Durability information is stored and

accessed in CES EduPack Opening a

LIMIT stage reveals a list of the

environments, each with a 4-point check box

for material selection Each heading is

linked to pages of Science notes, and each

environment name is linked to

Environmental notes pages like those

shown here, listing information relating to

the other factors shown in Figure 1

Level 2 are shown without brackets Those that are not in Level 2, but for which properties can be found in Level 3 are shown in brackets

Below this are two further notes The first lists inhibitors that slow the rate of attack by the environment, though they seldom prevent it entirely (Table B2 of Appendix B gives examples) Inhibitors are material-specific – thus the inhibitors for HCl attack of iron differ from those for HCl attack of aluminium or titanium The metal to which a given inhibitor applies is shown in brackets after the inhibitor name The second note simply indicates the underlying mechanism, more fully described in the Science notes attached to the headings

Table 3 Industrial sectors

water, soil Food processing Acetic acid, citric acid, sulphur dioxide, vegetable oils, fresh and

salt water, wine

Engineering manufacture Industrial fluids, Fuels and oil

Construction (housing, industrial building Soils, Built environments (Industrial, marine, rural) Radiation, Energy conversion (ic engines, steam and gas turbines) Thermal environments: Hot liquids and gasses

Marine engineering (shipping, off-shore engineering) Salt water, industrial solvents

Domestic (cooking, cleaning) Fresh and salt water, dilute acids and alkali, vegetable and animal

fats

4 Using the Durability data in CES EduPack

The use of the database is best illustrated by examples In each example the CES system has been opened in Level 2 Materials with Durability

Example 1 The waste stream of a fertilizer plant includes dilute sulfuric acid The dilute acid is stored in surface tanks some distance from the plant It is suggested that the ducting to carry the acid to the tanks could, most economically, be made of wood Is this a totally crazy suggestion?

• Browse: opening the records for Hardwood:oak or for Softwood: pine we find:

The suggestion should be taken seriously, provided the strength of the acid is below 10%

Softwood: pine

Durability: acids

Sulfuric acid (10%) Acceptable Sulfuric acid (70%) Unacceptable

Example 2 A polymer coating is sought to protect components of a

microchip processing unit from attack by hydrogen fluoride (HF)

• Tree stage: limit the selection to Polymers

• Limit stage: require Excellent in Hydroflouric acid (40%)

The results are shown in the box

• Opening the Environmental notes for Hydrofluoric acid

(40%) confirms that fluorocarbon polymers give good

protection, and provides information about inhibitors,

suggesting that steel components can be protected by doping the

HF solution with one of these

Hydrofluoric acid (40%), HF Preferred materials and coatings

Metals Polymers and composites Ceramics and glasses

Lead

Copper

Stainless Steel

Carbon Steels

(Monel)

(Hastelloy C)

(Platinum, Gold, Silver)

PTFE Fluorocarbon polymers Rubber

Graphite

Example 3 A food processing plant uses dilute acetic acid for

pickling onions The acid is piped to and from holding tanks Select

a suitable material for the pipes and tanks, given that, to have

sufficient strength and toughness to tolerate external abuse they

must be made of a metal

• Tree stage: limit the selection to metals

• Limit stage: require Excellent in Acetic acid (10%)

The results are shown in the box

• Opening the Notes for Acetic acid (10%) gives the following

information about preferred materials and coating

Metals Polymers and composites Ceramics and glasses

Aluminum

Stainless steel

Nickel

Nickel alloys

Titanium

(Monel)

HDPE PTFE

Glass (Porcelain) (Graphite)

The metals are essentially the same as those found by the limit search – the only difference is the inclusion of aluminum But the other two columns suggest an alternative approach: that of making the pipe work out of a cheap steel and either lining it with HDPE or PTFE, or enameling it to give a glass surface These are attractive alternatives since, in food processing, any leaching of metal ions into the product is unacceptable

Results of Limit stage

Commercially pure lead Commercially pure titanium Titanium alloys

Nickel-based superalloys Nickel-chromium alloys Stainless steel Tin

Results of Limit stage

Ionomer (I) Polychloroprene (Neoprene, CR) Polyethylene (PE)

Polypropylene (PP) Polytetrafluoroethylene (PTFE)

Example 4. Metal pipe work on an oil rig must carry hydrochloric

acid solution to acidify the well Use the database to explore ways of

providing and protecting the pipe

• Tree stage: limit the selection to metals

• Limit stage: require Excellent in Hydrochloric acid (10%)

The results are shown in the box HCl is a particularly aggressive

acid Only three alloys survive

• Opening the Notes for Acetic acid (10%) we learn that HCl is a

particularly aggressive acid, difficult to contain and transport

The preferred material and coating, and the inhibitors are listed

Hydrochloric acid (10%), HCl Preferred materials and coatings

Metals Polymers and composites Ceramics and glasses

Copper

Nickel and nickel alloys

Titanium

(Monel)

(Molybdenum)

(Tantalum)

(Zirconium)

(Platinum, Gold, Silver)

HDPE

PP GFRP Rubber

Glass

Inhibitors. Ethylaniline, mercaptobenzotriazole, pyridine and phenylhydrazine, ethylene oxide (all used for Fe),

phenylacridine (Al), napthoquinone (Al), thiourea (Al), chromic acid (Ti), copper sulphate (Ti)

Titanium would appear to be the best, though expensive, choice: its inherent resistance to attack by HCl is high, and inhibitors exist that give added protection The alternative, suggested by the table, is that the pipe work is lined with HDPE or enameled

Example 5 An auto maker is concerned about the consequences of the introduction of bio-methanol, CH3OH

or bio-ethanol C2H5OH into auto fuels The particular concerns are

(a) Corrosion of aluminum components, particularly the engine block, by methanol or ethanol

(b) Possible damage to GFRP or CFRP body panels of some models by spillage of methanol or ethanol-containing bio-fuels

Are the concerns justified? What can be done if they are?

Results of Limit stage

Commercially pure lead Stainless steel Titanium alloys

• Browse: opening the records for Cast aluminum alloys

and for Sheet molding compound (SMC) yields the

information shown in the boxes Clicking on the

environment name brings up the Notes pages, also

useful

Cast aluminum alloys are “Acceptable” in both alcohols –

not the highest rating, so some corrosion is possible The

problem, as the Note explains, is the take up of water,

which, if allowed, brings the risk of electro-chemical

corrosion Lobbying for the inclusion of inhibitors in the

fuel might be justified

SMC (and also CFRP) gets a more severe rating of

“Limited use” This is a cause for concern – prolonged

exposure to either of the two alcohols, if present in large

concentration in the fuel, could result in degradation of the

body panels It will be necessary to explore

alcohol-resistant surface coatings if the use of bio-fuels becomes

widespread

Example 6 As a materials consultant you are asked to prepare a survey of the strength and resistance of materials to strong sodium hydroxide, NaOH The client, the manager of a paper-making plant that uses NaOH

in one step of the paper-making process, is interested in metals, polymers and polymer based composites as alternatives for parts of the pipe work, valves and pumps

• Select: Custom – define you own subset Create a database that contains only the materials of interest to the client: metals, polymers and polymer-matrix composites

• Graph stage: make a Graph with Yield strength on the y-axis and Sodium hydroxide (60%) on the x-axis

• Label the materials by clicking on the bars Where the name is too long or for some other reason you want

to edit it, click twice, slowly, on the label When it turns blue you can edit it To reformat the color, type face or size, right-click on the label and select Format at the bottom of the menu that appears It lets you change the font and its size and color

• Add a title by clicking on the A in the tool bar above the chart

• Open the Environmental Notes for Sodium Hydroxide (60%)

The resulting chart, shown below, provide an overview at the CES Level 2 of strength of materials and their durability in strong NaOH of materials The Notes, also shown, give further information about where the environment is encountered and the materials that are most resistant to it

Sheet molding compound, SMC

Durability: alcohols, aldehydes, ketones

Ethyl alcohol (ethanol) Limited use Methyl alcohol (methanol) Limited use

Cast Al-alloys

Durability: alcohols, aldehydes, ketones

Ethyl alcohol (ethanol) Acceptable Methyl alcohol (methanol) Acceptable

alkali carbonates or lactates (Al),

Sodium hydroxide (60%) (caustic soda), NaOH

alumina, paper and bio diesel, and is used to clean and etch aluminum

and toxic Vapors are dangerous

Preferred materials and coatings

Nickel and its alloys

Stainless steels

PVC LDPE HDPE PTFE (PE-CTFE)

Glass Graphite

Figure 4 A chart made with the CES EduPack Level 2 with durability properties, surveying the durability of chosen material classes in NaOH

Figure 5 The Environmental notes for Sodium hydroxide (60%)