MTE401L Lab Manual PDF

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PDF of lab manual for mte 401L. Includes all experiments and all deliverables ...

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LABORATORY(MANUAL(MTE401L(( MTE401L:)Corrosion)and)materials)degradation)Laboratory) ( This(course(is(concurrent(with(the(lecture(of(the(same(name(MTE401.(The( laboratory(modules(complements(the(concepts(introduced(in(the(lectures(providing( a(hands(on(experience.(Corrosion(is(better(learned(by(doing,(students(will,(under( guidance(by(lecturer,(design(the(experiments(in(the(areas(of;( ( 1. Uniform(Corrosion,( 2. The(use(of(Electrochemistry( 3. Non-Uniform(Corrosion( a. Pitting(Corrosion( b. Crevice(Corrosion( 4. Galvanic(Corrosion( 5. Corrosion(principles(put(to(benefits,(assigned(as(special(projects,(concurrent( with(the(Uniform(corrosion(test.( a. Electroplating,( b. Cathodic(Protection,(( c. Anodizing,( d. Electropolishing.( 6. Stress(Corrosion(Cracking( ( 1.)Uniform)Corrosion)Test:)) ( Corrosion(is(the(degradation(of(materials(by(a(redox(reaction(with(its(environment( that(leads(to(the(loss(of(engineering(function.(Uniform(corrosion(takes(place(evenly( on(the(surface(of(the(material(where(discretely(random(grains(act(as(anodes(and( cathodes.(The(anode(is(the(place(where(the(anodic(reaction,(or(the(giving(of( electrons(takes(place.(The(cathode(is(the(place(where(the(complementary(reaction,( the(reduction(reaction(or(acceptance(of(electron(reaction(takes(place.(Electrons( transfer(through(the(metal(generating(electric(current(while(current(in(the( electrolyte(is(carried(by(the(ionic(species(in(the(environment,(also(known(as(the( oxidants.(This(balance(of(electrons(is(needed(for(corrosion(to(take(place.(If(by(any( means(this(electron(transfer(is(impede,(corrosion(ceases.(( ( Corrosion(is(an(inevitable(process(because(metals(are(electropositive(elements,( meaning(metals(are(always(willing(to(give(their(valence(electrons(up.(Most(metals( exist(in(nature(in(their(most(stable(form,(as(oxides.(The(corrosion(products(are( ceramic(materials(resulting(from(the(combination(of(Metals(and(Non-metals,(with( predominant(ionic,(covalent(or(both(types(of(bonds.( ( The(driving(force(of(corrosion(is(thermodynamics,(and(the(tendency(of(the(reaction( to(take(place(can(be(calculated(using(the(EMF(or(electro(motive(force(series.(In(the( EMF(series,(metals(are(ranked(in(terms(of(their(standard(electrochemical(potential,( measured(with(respect(to(a(reference(electrode,(the(Hydrogen(Reference(electrode.( The(Hydrogen(reference(electrode(has(an(EMF(of(0.000(V,(that(has(been(arbitrarily( set(for(the(redox(equilibrium;( By(Dr.(Juan(Carlos(Nava(12/17/2016(

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LABORATORY(MANUAL(MTE401L(( ( 2H(+((+(2(e(-((à((H2((g)((( ( ( ( ( Figure(1,(shows(the(EMF(series(for(most(metals.( (

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Figure)1.)Electro-motive)Force)Table) ( It(is(worth(noticing(that(every(metal(more(noble(than(the(hydrogen(electrode(will( have(no(corrosion(tendencies(in(aqueous(or(acidic(environments.( ( When(studying(corrosion,(it(is(essential(to(identify(both(redox(reactions.(Due(to(their( natural(tendencies,(metals(oxidation(is(the(obvious(oxidation(reaction.(For(the(

By(Dr.(Juan(Carlos(Nava(12/17/2016(

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LABORATORY(MANUAL(MTE401L(( reduction(reaction,(we(need(to(look(into(the(electrolyte(or(environment(to(identify( the(most(probable(reduction(reactions.(The(EMF(series(is(essential(to(validate(these( predictions.( (

( Figure)2.)Another)version)of)the)EMF)series.) ( In(identifying(these(possible(oxidizers((easy(to(be(reduced(species)(we(look(for( reactions(involving(metal(ions(with(higher(valence(states(like(ferric,(Fe3+,(cupric,( Cu2+,(stannic,(SN4+,(ionic(species,(and(oxygen(reduction(reactions(whose(potentials( depend(on(the(pH(of(the(aqueous(solutions.(All(these(redox(reactions(have(EMF( nobler(with(respect(to(the(hydrogen(reduction(reaction,(therefore,(they(will(be(more( effective(as(oxidizers(when(in(solution(in(aqueous(media.(( ( To(calculate(the(spontaneity(of(the(corrosion(reaction(we(use(the(following( expression;( ( ( ( ( ΔG(=(-(nFE( ( ( ( (2)( ( Where(n"is(the(number(of(electrons(transferred(determined(from(the(stoichiometric( and(charge(balance(of(both(redox(reactions.(E(is(equal(to(the(total(EMF(of(the( reaction(using(the(corresponding(EMF’s(from(Figure(2,(taking(into(consideration( reversal(of(the(voltage(sign,(because(in(the(EMF(all(redox(reactions(are(written(as(

By(Dr.(Juan(Carlos(Nava(12/17/2016(

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LABORATORY(MANUAL(MTE401L(( reduction(reactions.(E(is(the(algebraic(sum(of(the(EMF’s(corresponding(to(the(two( predominant(redox(reactions.(If(E(is(positive(the(free(energy(of(the(reaction(will(be( negative(suggesting(spontaneity(of(the(reaction.(If(the(free(energy(is(positive,(it(only( means(that(the(reverse(reaction(is(spontaneous(and(to(make(it(happen(external( manipulating(tools(will(be(needed,(i.e.(a(power(supply,(or(potentiostat.( ( Another(tool(that(is(important(in(the(understanding(and(design(of(the(uniform( corrosion(tests(is(the(Galvanic(Series.(Figure(3(shows(the(Galvanic(series(and(Figure( 4(depicts(the(Galvanic(cell(action.( (

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( Figure)3.)The)Galvanic)series)

By(Dr.(Juan(Carlos(Nava(12/17/2016(

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LABORATORY(MANUAL(MTE401L((

((

( Figure)4.)The)Galvanic)action.) ( The(Galvanic(series(arrange(the(metals(and(alloys(with(respect(to(the(materials( susceptibility(to(corrode(in(a(specific(environment.(This(series(is(most(commonly( reported(for(Sea(water(as(the(electrolyte,(but(the(ranking(is(almost(the(same( regardless(of(the(nature(of(most(industrial(aqueous(media.(An(active(metal(or(alloy( has(a(greater(tendency(to(corrode(than(the(more(noble(metal.( ( There(are(alloys,(in(particular(those(made(of(Cu,(where(the(galvanic(nature(of(the( alloying(elements(with(respect(to(Cu,(tend(to(preferentially(dissolve(in(electrolytic( media.(This(type(of(corrosion(is(Uniform(corrosion(but(it(is(usually(listed(as(a( particular(mode(of(corrosion(known(as(“dealloying”.(Brass,(Cu-Zn,(Bronze,(Cu-Sn,( and(gray(cast(steel,(Fe-Graphite,(are(classic(examples.( ( 1.1)Uniform)Corrosion)Testing)Methods:)) ( There(are(two(primary(methods(that(are(used(in(industry(to(assess(Uniform( Corrosion(susceptibility;( ( 1. The(Interval(Test(Method,( 2. The(ASTM(Standard(for(immersion(testing(G31.( ( By(Dr.(Juan(Carlos(Nava(12/17/2016(

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LABORATORY(MANUAL(MTE401L(( The(selection(of(the(testing(method(is(particularly(chosen(to(better(represent(the( practical(use(of(the(alloy.(For(most(containment(materials(selection,(the(interval(test( is(the(preferred(approach,(while(for(other(test(conditions(the(ASTM(G31(offers( flexibility.(In(the(interval(test(approach(the(corrosion(engineer(gathers(information( regarding(the(corrodibility(of(the(metal(and(the(corrosiveness(of(the(electrolyte.(The( immersion(test(allows(evaluating(the(impact(of(exposure(conditions,(fully(immersed( or(partially(immersed.(Common(to(the(success(of(the(test(in(terms(of(validation(and( predictability(is(the(ratio(of(electrolyte(volume(to(surface(sample(area.(Enough( solution(is(needed(to(eliminate(the(impact(of(original(oxidizer(depletion.(In( corrosion(all(results(are(normalized(to(surface(area(in(order(to(eliminate(the(impact( of(geometry(on(the(predicted(corrosion(rates.(Figure(5,(depicts(the(Planned(Interval( Test(philosophy.( (

( ( Figure)5.)The)planned)interval)corrosion)test) ( The(class(text-book(explains(the(method(of(data(analyses(for(the(interval(test.( Students(are(encouraged(to(review(the(method(prior(to(test(procedure(selection.( The(interval(test(will(allow(the(students(to(determine(if(the(corrosivity(of(the( solution(changes(with(time(and(if(the(materials(are(corroding(at(a(consistent(rate.( ( The(uniform(corrosion(lab(lasts(from(four((4)(to(six((6)(weeks.(Students(are( encouraged(to(select(metal/electrolyte(combinations(relatable(to(them.(Students(are( also(allowed(to(be(creative(in(their(experimental(design.(( ( 1.2)Elements)of)practice)to)all)groups)are)as)follows:) ( 1. Dimension(your(samples,(

By(Dr.(Juan(Carlos(Nava(12/17/2016(

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LABORATORY(MANUAL(MTE401L(( 2. Ultrasonically(clean(the(samples(with(Methanol,( 3. Air(dry(the(samples,( 4. Record(the(initial(weight(of(the(samples(using(analytical(balance(with(0.1(mg( sensitivity,( 5. Repeat(procedure(after(each(test(period,( 6. Record(data(in(lab(book,( 7. Maintain(good(safety(practices,( 8. All(waste(solutions(are(to(be(disposed(properly.( ( Metal(samples(are(provided(and(students(can(purchase(their(own(if(what(they(would( like(to(test(other(metal(or(alloy(of(common(use.(Prior(to(experimentation,(each(team( will(prepare(a(test(protocol(indicating(the(following,( ( 1. Describe(the(scenario(selecting(Metal/alloy(and(electrolyte,( 2. Identify(any(standards(to(be(use(as(guidelines,( 3. Redox(reactions,( 4. Validation(of(hypothesis(regarding(corrodability(using(the(EMF(series(and( thermodynamics,( 5. Explanation(of(test(and(calculations(for(electrolyte(preparation,( 6. Selection(of(test(containment(and(design(of(experiment,( 7. Disposal(of(electrolyte(and(estimated(quantities,( 8. MSDS(for(all(chemicals(to(be(used.( ( No(test(will(be(initiated(until(the(content(of(the(pre-lab(test(has(been(discussed(with( the(instructor.(Assignment(on(the(use(of(the(EMF(will(be(provided(for(credit(toward( course(grade.(ASTM(standards(are(available(on-line(through(the(CPP(library.(Copies( of(the(Standards(must(be(attached(to(the(lab(book.( ( 2.)The)use)of)electrochemistry)for)the)study)of)Uniform)Corrosion:) ) The(corrosion(reaction(is(a(redox(reaction(that(results(into(the(flow(of(electrons( between(cathodes(and(anodes(resulting(into(an(electric(current(that(is(a(tangible( measurement(of(the(corrosion(rate.(Therefore,(it(is(appropriate(to(use( Electrochemistry(as(a(means(of(determining(corrosion(rates,(a(process(that(could( result(being(more(economic(than(exposure(testing.(( ( 2.1)Elements)of)an)electrochemical)cell:) ( To(simulate(the(corrosion(process,(a(three-electrode(electrochemical(cell( arrangement(is(recommended.(The(three(electrodes(are(identifying(as(follows,( ( 1. Working(Electrode((WE):(This(is(the(electrode(that(represents(the(material( that(will(be(tested,( 2. Reference(Electrode(((RE):(This(is(a(non-polarizable(electrode(that(is(used(to( measure(the(voltage(when(short-circuited(with(the(WE.(Non-polarizable(

By(Dr.(Juan(Carlos(Nava(12/17/2016(

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LABORATORY(MANUAL(MTE401L(( means(that(no(appreciable(current(flows(through(the(electrode(within(a( reasonably(large(voltage(span,( 3. Counter(Electrode((CE):(This(is(the(electrode(where(the(counter(redox( reaction(takes(place.(The(CE(is(used(to(measure(the(current(in(the( electrochemical(circuit.( ( Figure(6(depicts(the(set(up(arrangement(to(conduct(electrochemical(polarization( measurements.( (

( ( Figure)6.)Electrochemical)measurements)set-up.) ( A(potentiostat(is(used(to(control(the(voltage(and(to(measure(the(current(in(the(threeelectrode(electrochemical(cell(arrangement.(Most(potentiostats(also(operate(as( galvanostats,(where(instead(of(controlling(voltage,(the(current(is(control(at(the(WE( and(the(voltage(is(measured.(All(potentiostats(come(with(software(that(is(used(to( collect(and(analyzed(polarograms.(Polarograms(are(two-dimensional(plots(of(voltage( vs(current.(( ( Students(are(trained(on(the(used(of(electrochemical(techniques(following(the(ASTM( G59(standard(for(the(determination(of(corrosion(rates.(The(procedure(introduces( the(following(concepts,( ( 1. Open(Circuit(Voltage(or(OCV,(this(voltage(represents(the(condition(of( equilibrium(at(the(surface(where(both(oxidation(and(reduction(reactions(are( taking(place(at(the(same(rate(with(a(net(current(of(zero.( 2. Resistance(Polarization,(a(technique(where(the(surface(redox(equilibrium(is( mildly(disturbed(by(polarizing(the(surface(-/+(20(mV(around(the(OCV(to(

By(Dr.(Juan(Carlos(Nava(12/17/2016(

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LABORATORY(MANUAL(MTE401L(( estimate(the(resistance(to(electron(transfer,(a(preliminary(measurement(of( the(corrosion(rate,(Figure(7.( (

( ( Figure)7.)Resistance)Polarization)output.) ) The(linear(polarization(scan,(LPR,(must(show(a(zero(current,(otherwise,(let(the( system(rest(to(attain(a(condition(of(equilibrium,(and(try(again.(The(results(of(the( ASTM(G59(are(only(valid(if(a(state(of(equilibrium(has(been(attained(prior(to(any( measurements.( ( 3. Dynamic(polarization,(a(technique(that(allows(the(determination(of(the(Tafel( constants(related(to(control(by(electron(transfer(reactions.(The(potential(in( the(WE(is(scanned(between(-/+(400(mV(with(respect(to(the(OCV.(The( Cathodic(scan(most(depict(activation(polarization(control,(which(means( electron(transfer(control(at(the(WE(surface.(If(the(cathodic(scan(shows( concentration(polarization(control,(as(illustrated(by(a(limiting(current(in( Figure(9,(the(experimentalist(must(stop(the(experiment(and(implement(either( and(increase(in(the(concentration(of(the(oxidizer(or/and(induce(convection.( The(dynamic(polarization(is(repeated(until(activation(control(is(observed(in( the(cathodic(scan.(Polarograms(as(the(one(shown(in(Figure(9(are(useless(for( the(purpose(of(the(ASTM(G59(standard.(The(cathodic(scan(is(used(to( determine(the(cathodic(TAFEL(constant(as(illustrated(in(Figure(8.(The(TAFEL( constant(is(given(by(the(rise(in(voltage(within(one(current(decade.(The( By(Dr.(Juan(Carlos(Nava(12/17/2016(

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LABORATORY(MANUAL(MTE401L(( intercept(of(the(TAFEL(line(and(the(pseudo(OCV(from(the(polarogram(is(then( used(to(determine(the(anodic(TAFEL(constant.(There(are(no(limiting(currents( in(the(anodic(scan(because(plenty(of(WE(is(available(to(oxidize.(( (

(

( Figure)8.)Dynamic)Polarization)polarogram.) (

( Figure)9.)Cathodic)scan)showing)limiting)current.)Unacceptable)for)ASTM)G59) calculations.( By(Dr.(Juan(Carlos(Nava(12/17/2016(

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LABORATORY(MANUAL(MTE401L(( Dynamic(polarograms(are(also(useful(to(identify(passivation(behavior(as(the( one(illustrated(in(Figure(10.( (

( ( Figure)10.)Passivation)behavior)as)indicated)by)a)reduction)in)current) during)anodic)polarization.) ( Dynamic(polarization(is(also(useful(in(revealing(the(tendency(of(a(passivating( material(to(experience(pitting(corrosion.(Pitting(corrosion(is(illustrated(in( Figure(11.(As(the(voltage(scan(is(reverse(in(the(anodic(polarization,(a( hysteresis(loop(will(indicate(pitting(potential.(This(tendency(can(also(be(used( to(predict(any(susceptibility(to(crevice(corrosion.( ( If(more(than(one(material(is(tested,(the(superposition(of(all(the(recorded( dynamic(polarograms(can(be(used(to(identify(the(risk(of(galvanic(corrosion( by(observing(changes(in(the(pseudo(OCV.(The(more(positive(OCV(will(identify( a(nobler(material(while(the(more(negative(OCV(will(rank(the(material(as( active(in(the(particular(electrolyte.((Figure(12(illustrates(three(dynamic( polarograms(from(a(material(that(has(been(modified.(The(polarograms( illustrates(the(impact(of(the(modification(on(the(electrochemical(response,( with(the(materials(becoming(nobler(with(respect(to(the(base(alloy,(the(SS.( (

By(Dr.(Juan(Carlos(Nava(12/17/2016(

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LABORATORY(MANUAL(MTE401L((

( ( Figure)11.)Dynamic)anodic)polarization)showing)hysteresis)loop) revealing)a)tendency)to)pit)and)to)be)susceptible)to)crevice)corrosion.) (

( Figure)12.)Dynamic)polarogram)comparing)electrochemical)responses) as)a)result)of)base)alloy)modifications.) (

By(Dr.(Juan(Carlos(Nava(12/17/2016(

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LABORATORY(MANUAL(MTE401L(( 4. The(algebraic(manipulation(of(the(outputs(as(per(the(ASTM(G59(instructions( allows(for(the(calculation(of(the(corrosion(current(and(subsequently(the( corrosion(rate.( ( The(versatility(of(the(methods(will(be(illustrated(by(pre-recorded(polarograms( identifying,(by(the(interpretation(of(Potential-Current(trends,(corrosion(types(other( than(uniform(corrosion(and(the(connection(between(electrochemistry(and(the( generation(of(galvanic(series(for(materials(selection.( ( The(mixed(potential(theory(and(the(concept(of(exchange(current(density(are( introduced(in(the(lecture(to(easy(the(introduction(of(electrochemical(data( interpretation.( ( The(thermodynamic(equilibrium(phase(diagram,(the(Pourbaix(diagram,(is(also( introduced(as(a(thermodynamic(tool(to(predict(the(conditions(that(lead(to( continuous(corrosion,(passivity,(or(metal(immunity,(Figure(13.( (

Figure)13.)General)Pourbaix)diagram.)

By(Dr.(Juan(Carlos(Nava(12/17/2016(

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LABORATORY(MANUAL(MTE401L(( In(this(laboratory(practice,(students(will(be(provided(with(prerecorded( electrochemical(data(gathered(from(various(metals(and(electrolytes.(The(students( will(use(the(ASTM(G59(to(execute(calculations(and(issue(materials(selection( recommendations.(( ( The(results(of(the(exercise(will(be(presented(within(a(limited(time(of(6(minutes.(The( concepts(of(electrochemistry(are(to(be(presented(not(as(a(technical(lecture(but(in(a( format(that(leads(the(audience(to(appreciate(the(versatility(and(easiness(of(the( approach(to(conduct(Uniform(corrosion(testing(comparing(to(traditional(long(term( exposure(testing.(The(element(of(economics(needs(to(be(highlighted(and(justified.( Each(group(will(approach(the(presentation(as(an(equipment(vendor,(as(a(consultant( provider,(or(as(an(employee.(Presenters(will(be(judged(on(the(quality(of(the( presentation(and(the(delivery(of(the(presenter.(Presenters(are(chosen(at(random.( The(Presenter(is(free(to(use(any(oral(communication(method(that(better(represents( their(position(within(a(6(minutes(allotted(time.(Time(in(excess(of(6(minutes(will(be( penalized.( ((( 3.)Non-Uniform)Corrosion)test:) ) Non-uniform(corrosion(takes(place(on(the(surface(of(metals(and(alloys(that(have(a( tendency(to(spontaneously(passivate(or(it(can(be(induced(by(elements(of(design(that( allows(for(the(formation(of(electrolyte(puddles(or(occluded(areas.(The(driving(force( is(the(concentration(cell(action(effect(caused(by(differences(in(electrolyte( compositions(between(the(environment(beneath(the(compromised(passive(layer(or( in(the(occluded(area,(Figure(14.(Typical(electrolyte(is(seawater(where(acidification(of( the(localized(electrochemical(cell(is(the(result(of(charge(neutrality(making(the(local( environment(more(corrosive(than(the(bulk(solution.(( (

((

(

( Figure)14.)Mechanism)of)non-uniform)corrosion.) ( For(the(planning(of(the(non-uniform(corrosion(test(the(students(are(recommended( to(search(for(relevant(ASTM(standards(and(to(make(use(of(all(tools(provided(during( By(Dr.(Juan(Carlos(Nava(12/17/2016(

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LABORATORY(MANUAL(MTE401L(( the(introduction(of(uniform(corrosion.(The(students(must(plan(their(test(accordingly( to(provide(evidence(of(localized(corrosion(within(a(week(period.(Testing(materials( and(other(identified(supplies(are(provided.(No(testing(to(be(initiated(without( properly(evaluating(the(test(approach(with(the(instructor.( ( The(deliverable(is(a(three((3)(minute(technical(presentation(on(localized(corrosion.( Students(are(allowed(the(use(of(any(tools(that(better(support(their(deliverable.(A( session(of(questions(will(follow.(Responses(will(be(considered(as(part(of(the( evaluation.(After(all(presentations(are(done,(the(students(will(judge(and(rank(the( presentations(based(on(technical(content,(team(originality,(delivery(and(style.(Every( judgment(will(be(properly(substantiated(with(specific(details.(Presenters(are(chosen( at(random.( ( 4.)Galvanic)corrosion)test:) ( Galvanic(corrosion(takes(place(when(two(materials(with(dissimilar(reactivity(in(a( given(environment(are(electrically(connected.(Galvanic(corrosion(can(be(induced(by( elements(of(design(that(allows(for(the(joining(of(dissimilar(materials(to(be(exposed( to(a(given(electrolyte,(Figure(15.(The(driving(force(is(the(difference(in(the(EMF(of(the( metals(and(alloys(in(a(given(electrolyte.(The(EMF(and(galvanic(series(are(excellent( resources(to(use(in(the(evaluation(of(this(form(of(corrosion.(Segregation(of(alloying( elements(during(welding(and(the(heat(treatment(of(stainless(steels(can(also(lead(to( localize(galvanic(corrosion(effects.(The(effect(of(the(cathode(to(anode(surface(area( rat...