The Evidence Guide provides advice on assessment and must be read in conjunction with the Performance Criteria, Required Skills and Knowledge, the Range Statement and the Assessment Guidelines for the Training Package.

Overview of assessment

A person who demonstrates competency in this unit must be able to determine corrosion prevention strategies for metal and alloys. Critical aspects for assessment and evidence are required to demonstrate competency in this unit.

Critical aspects for assessment and evidence required to demonstrate competency in this unit

It is essential that competence is demonstrated in the ability to:

correctly identify metallurgical processes involved in corrosion and corrosion prevention;

select corrosion prevention strategies and techniques appropriate to metal or alloy application and client needs

prepare instructions for corrosion prevention for client and other appropriate personnel.

Relationship to other units

This unit may be assessed concurrently with other relevant units.

Assessment method and context

Assessors must be satisfied that the person can consistently perform the unit as a whole, as defined by the elements, performance criteria, skills and knowledge. A holistic approach should be taken to the assessment.

Assessors should gather sufficient, fair, valid, reliable, authentic and current evidence from a range of sources. Sources of evidence may include direct observation, reports from supervisors, peers and colleagues, project work, samples, organisation records and questioning. Assessment should not require language, literacy or numeracy skills beyond those required for the unit.

The assessee will have access to all techniques, procedures, information, resources and aids which would normally be available in the workplace.

The method of assessment should be discussed and agreed with the assessee prior to the commencement of assessment.

Resource implications

This section should be read in conjunction with the range of variables for this unit of competency. Resources required include suitable access to an operating plant or equipment that allows for appropriate and realistic simulation. A bank of case studies/scenarios and questions will also be required to the extent that they form part of the assessment method. Questioning may take place either in the workplace, or in an adjacent, quiet facility such as an office or lunchroom. No other special resources are required.

This describes the essential skills and knowledge and their level, required for this unit.

Required skills:

select appropriate metallurgical principles to reduce corrosion

apply metallurgical principles to particular manufacturing, engineering and structural situations

refer solutions to the original aim of the application.

quote solutions in appropriate units, using appropriate significant figures.

quote limitations of corrosion prevention or minimisation strategies.

Required knowledge:

Competency includes sufficient knowledge of:

basic metallurgical principles (as given in the range statement)

limitations of selected metallurgical principles

The range statement relates to the unit of competency as a whole. It allows for different work environments and situations that may affect performance. Bold italicised wording, if used in the performance criteria, is detailed below. Essential operating conditions that may be present with training and assessment (depending on the work situation, needs of the candidate, accessibility of the item, and local industry and regional contexts) may also be included.

Codes of practice/standards

Where reference is made to industry codes of practice, and/or Australian/international standards, it is expected the latest version will be used.

Metallurgicaltechniques and principles

Corrosion and Society

definition of corrosion

environments

corrosion damage

classificiation or corrosion

cost of erosion

social implications

Corrosion Principles

Electrochemical aspects

electrochemical reactions and chemical corrosion, galvanic cells, anode reactions, cathode reactions, concentrations cells, polarisation, passivity, pourbaix diagrams (simplified Pourbaix diagrams for Al, Fe and Zn), the driving force of corrosion, the rate of corrosion

Environmental effects

oxygen and oxidisers, velocity, temperature, corrosive concentration, corrosion environments (water, soil, atmosphere, dry gasses)

Metallurgical aspects

metal structures (defects, grain boundaries, second phases, cold work, residual stress), galvanic series, immunity, passivity.

Corrosion at Elevated Temperatures

Mechanism of oxide film growth:

rate laws

oxide defect structures

Pilling-Bedworth rule

oxidation of alloys

catastrophic oxidations

de carburisation

high temperature resistent alloys

Forms of corrosion

Uniform corrosion (general corrosion)

Galvanic corrosion

Crevice corrosion

Pitting corrosion

Fretting corrosion

Selective attack (leaching)

Intergranular corrosion

Stray current corrosion (electrolysis)

Erosion corrosion and cavitation damage

Stress corrosion cracking

Corrosion fatigue

Hydrogen damage

Microbial corrosion

Basic principles of Corrosion Control

Material selection

metals and alloys, metal purification, nonmetallics, stress relief

Alteration of environment

changing media, temperature, velocity, oxygen concentration, etc.

Corrosion protection

cathodic protection, anodic, protection and passivation, corrosion inhibitors, chemical conversion coatings, metal coatings, corrosion-preventing paints, coatings of plastic and rubber, temporary corrosion prevention.

Corrosion prevented by design

wall thickness, design rules (streamlining, stagnation, crevices, metallic contact, etc.)

Corrosion Characteristics of common alloys

Steel and cast iron

Stainless steel

Aluminium and its alloys

Copper and its alloys

Methodology of corrosion investigations

Corrosions testing

Corrosion monitering

Electrochemical investigations

Physical methods

Sources of information

Reference texts

Manufacturers' catalogues and industrial magazines

Websites

Use of phone, email and fax information gathering