Nace Chapters 1-5 Exam 3 Study Guide With 100% Complete Solution, Exams of Advanced Education

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Nace Chapters 1-5 Exam 3 Study Guide

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Corrosion description Is usually described by its results. Familiar terms include rust, scaling, discoloration, oxidation, pitting, etc. Corrosion The deterioration of a substance, usually a metal, or its properties because of a reaction with its environment. The most common product of corrosion is an Oxide of iron "rust" Passivation The formation of a thin, tightly adherent surface layer. Formed from the corrosion product, that slows the rate of corrosion. All corrosion of iron at normal ambient conditions is an electrochemical process. How do electrons and ions travel. Electrons travel through metal, Ions travel through an electrolyte. Corrosion is established as DC circuits. The greater the flow in the corrosion circuit. The greater the metal loss. Anode is the part of the metal that corrodes (i.e., dissolves in the electrolyte). The metal that dissolves is does so in the form of positively charged ions. Metal deterioration occurs at the Anode. It is the portion of the cell that where metallic iron is first converted to another substance. Cations

positively charged ions Cathode is the more noble region on the electrode (metal surface) where the electrons are consumed. While oxidation occurs at the _____, reduction occurs at the _____ Anode, Cathode Metallic Pathway Metal connecting an anode to a cathode in a corrosion cell and allows for the passage of electrons. Generated at the anode, to the cathode. Electrolyte The medium that conducts the ionic (rather than electronic) current. Ions positively and negatively charged atoms. If anodes and cathodes remain in the same place for a period of time, the corrosion is, localized and pitting corrosion occurs. Mill Scale is: A blue-black layer of iron oxide Cathodic relative to the substrate Generally removed prior to painting. Galvanic Series is a list of materials in order of their corrosion potential, with the most easily corroded or, or most active, at the top, and the least easily corroded or least active, at the bottom. is sea water at 25 degrees c. Factors that affect the rate of corrosion Oxygen: Temperature: Chemical Salts: Humidity: Pollutants and Acid Gases: How does oxygen affect corrosion Like water, oxygen increases the rate of corrosion. How does temperature affect corrosion

Corrosion reactions are electrochemical in nature and usually accelerated with increasing temperature; therefore, corrosion proceeds faster in warmer environments than in cooler ones. How do chemical salts affect corrosion They increase the rate of corrosion by increasing the efficiency (conductivity) of the electrolyte. What is the most common chemical salt Sodium chloride, a major element in seawater. How does humidity affect corrosion Humidity and time of wetness play a large role in promoting and accelerating corrosion rates. Corrosion can occur without visible water, but the rate significantly decreases below 60% relative humidity. How do Pollutants and Acid Gases affect corrosion: In addition to the direct effect of chemical attack, these materials reduce the electrical resistance of the electrolyte. Reduction of resistance in the corrosion cell permits higher corrosion currents so increased corrosion rates occur. Two broad classifications of corrosion: General and Localized General corrosion:

• results in a relatively uniform loss of material over the entire surface
• results in a general thinning of the affected surface
• relatively easy to inspect
• does not cause catastrophic failures Localized corrosion: Occurs at discrete sites on the metal surface. The areas immediately adjacent to the localized corrosion normally corroded to a much less extent if it all. Often difficult to inspect. Corrosion activities at the localized corrosion sites may vary with changes such as: Defects in the coatings Changes in contaminates and pollutants Changes in the electrolyte The predominant forms of localized corrosion found on offshore structures are: pitting and crevice corrosion. Pitting Corrosion Primarily occurs at distinct spots where deep pits are produced. The bottom of pits are anodes in a small, localized corrosion cell. Deep, even fully penetrating pits can, develop with only a relatively small amount of metal loss.

Crevice Corrosion:

• Occurs on a metal surface that is shielded from full exposure to the environment because of the close proximity of another material that forms a narrow gap between them
• Common in situations where there is metal-to-metal contact Corrosion Control methods: Design Inhibitors Material selection Cathodic protection Protective Coatings Splash zone systems Alteration of the environment. General Duties of the inspector are Observe Test Verify conformance to the specification (with documentation) Report The inspectors role a quality control technician who is primarily responsible for observing and reporting the technical aspects of a coating project and its conformance or deviation from the project specification. Inspectors should observe The job site for safety issues that may affect themselves or the contractor The weather conditions; observe, monitor and document The surface preparation The coating application Coating cure prior to return to service Documentation may include: Detailed written daily reports, inspection logs, routine reports, reports for weekly progress meetings, daily entries in a project log book, a daily inspection report using standardized forms, routine reports, monthly or quarterly reports With the proper inspection reports from previous coating projects managment could: Detect and tag design defects for review by the engineering group for future work Evaluate coating performance Determine realistic annual cost data on each coating system Develop a sound ongoing Maintenace program Good records can provide maintenance departments with detailed information on:

What was coated What materials were used When coating was done How it was done By whom it was done At what cost it was done What knowledge was retained in lessons learned Material Inventory Reports should include: The name of the material Quantity of on-site material Material batch numbers Date of the material's arrival on-site In regard to material inventory, it is good practice to: Keep coatings with the same batch number together Utilize first in first out rotation of materials A good coating specification contains Scope of work Terms and Definitions Reference standards and codes Safety Pre-job conference Surface preparation Coating materials (includes coating schedule) Sample coatings Workmanship Application Work Schedule (sequence of work to be done) Repairs and Remedial coating work Inspection Documentation MSDS includes Toxicity Health Effects First Aid Reactivity Storage Disposal PPE Spill handling procedures

How does NACE define the inspector's role? The inspector's role is that of a quality control technician responsible for observing and reporting conformance or deviation from the project specification. What is the inspector's responsibility when it comes to safety on the project? Safety enforcement is not the responsibility of the inspector; however, it is her responsibility to report any issues that may affect the project. Name some tests that may need to be conducted during surface preparation and coating operations. Temperature Relative humidity Dew point Anchor Profile Surface cleanliness Name some of the documentation/reports that may be required to be maintained on a coatings project. Daily/Weekly summary Material usage report Manpower and equipment Non-conformance and conformance What are the most important characteristics of a good report. Objective Accurate Detailed What is the inspector's primary responsibility and what should the inspector not do as it pertains to the specification. The inspectors primary responsibilty is to "enforce" the specification. The inspector is NOT to make changes to the specification for any reason. What type of information could you expect to find on a Product Data Sheet. Surface preparation and application information such as recommended level of surface cleanliness, recommended application methods and equipment such as tip sizes. Enviromental parameters for application such as max/min temperatures, curing times, recoat windows. Coatings Specification Formal, structured document containing information on a project (scope, terms, schedule, inspection, etc.) Instrumentation Calibration History Reports Reports that normally contain information on how frequently each instrument is to be or has been calibrated.

Quality Assurance (QA) Any systematic process that checks whether a product or service being developed is meeting specified requirements. Quality Control (QC) Procedure intended to ensure that a manufactured product or performed service meets the requirements of the client or customer. At night steel usually Radiates heat and cools to below air temperature. During the day Steel usually absorbs heat and it is usually warmer than the air temperature. Application at incorrect temperatures can cause defects such as Blistering Pin holing Cratering Dry spray Mud cracking ASTM D Standard Guide for Painting Inspectors. States that the minimum surface temperature for coating is usually 40F. It could be as low as 0F for cold curing one- or two-component systems or 50F for conventional two-component systems. The maximum surface temperature for application is typically 125F unless otherwise clearly specified. A surface that is too hot may cause the coating solvents to evaporate so fast that the application is difficult, blistering takes place or a porous film results. Most epoxy formulas stop the curing process below 50F Coating should only be applied to a substrate when that substrate is 5F above the determined dew point in order to prevent moisture on the surface from being coated. Relative Humidity (RH) is a measure of the amount of moisture in the air compared to saturation level (the amount it can hold at a given temperature) and may affect the coating operation because either too much or not enough relative humidity. Why does relative humidity matter

Typically there solvents in the coating film that need to evaporate and if the relative humidity is too high, there is no space for the solvent to evaporate. If this happens, the solvent that remain in the coating cause problems with the film such as solvent entrapment and lack of curing. dew point is the temperature at which moisture begins to form on a steel surface. It is the temperature to which a volume of air must be cooled in order to reach saturation. How can wind speed affect coatings Blow abrasives past the boundaries of the abrasive-blast work area to an area where coatings are being applied. Cause excessive drift or overspray of sprayed coatings Accelerate solvent evaporation after application Contribute to the formation of dry spray how does a sling psychrometer work

• As the instrument is spun, evaporation occurs in the wet thermometer and the resulting temperature is lower (energy was lost) than the dry bulb temperature.
• The drier the air, the greater the cooling.
• The larger difference between wet bulb and dry bulb temps, the lower the relative humidity. how to use a sling psychrometer Saturate the sock with clean water. Whirl the instrument rapidly for about 40 seconds. Read the Wet-bulb temperature. 3 consecutive readings. Standard Test Method for Measuring Humidity with a Sling Psychrometer ASTM E337-02 Method B Identify some of the defects that can be caused by incorrect application temperatures. Failure to cure Too rapid solvent evaporation Poor film formation What are some common errors when using an electric hygrometer Failure to acclimate the instrument to the environment with adequate time.