PAINTING INSPECTION

B.G.A.S. PAINTING INSPECTION WELCOME LEVEL 23 COURSE TUTOR TREVOR MYERS EXAMINATION DETAILS 1st PAPER, LEVEL 3, NARRATIVE QUESTIONS. 2nd PAPER, LEVEL 2, NARRATIVE QUESTIONS. PRACTICAL EXAMINATION, USE OF GAUGES ETC. ORAL EXAMINATION, REVIEW OF QUESTION

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B.G.A.S PAINTING INSPECTION

WELCOME LEVEL 2/3

COURSE TUTOR

TREVOR MYERS

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LEVEL 2/3

EXAMINATION DETAILS 1st PAPER, LEVEL 3, NARRATIVE QUESTIONS.

2nd PAPER, LEVEL 2, NARRATIVE QUESTIONS.

PRACTICAL EXAMINATION, USE OF GAUGES ETC.

ORAL EXAMINATION, REVIEW OF QUESTION

PAPERS

CLOSED BOOK

EXAM

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CORROSION THEORY

03 FACTORS NEEDED FOR CORROSION TO OCCUR

1 ANODE, a positively charged area.

2 CATHODE, a negatively charged area.

3 ELECTROLYTE, a substance which will conduct a current and be broken down by it.

IE WILL DISSOCIATE INTO POSITIVE AND

NEGATIVE IONS

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ANODES CORRODE THE COMBINATION OF

ELEMENTS ( OXIDATION) TAKES PLACE AT THE

ANODE.

CATHODES ARE PROTECTED, HYDROGEN IS

EVOLVED AT THE CATHODE AS THE ELECTROLYTE DISSOCIATES INTO POSITIVE AND NEGATIVE

IONS

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FACTORS ACCELERATING CORROSION

1 TEMPERATURE, THERMODYNAMICALLY UNSTABLE

AS THE STEEL HEATS UP, IT GAINS MOLECULAR

FREEDOM, BECOMES MORE ACTIVE, AND UNDERGOES CORROSION MORE READILY

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FACTORS ACCELERATING CORROSION

2 HYGROSCOPIC (OSMOTIC) BLISTERS

TINY, PIN HEAD SIZE, WATER

FILLED BLISTERS CAUSED BY

HYGROSCOPIC SALTS

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FACTORS INFLUENCING CORROSION

3 AEROBIC CONDITIONS, PRESENCE OF OXYGEN

INTRODUCE OXYGEN, DOUBLE THE IONS

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4 PRESENCE OF SOME BACTERIA ON THE SURFACE S.R.B’s SULPHUR REDUCING BACTERIA

M.E.M’s METAL EATING MICROBES

USUALLY SMALL HOLES WHICH FOLLOW THE

DIRECTION OF GRAVITY, NOT UNLIKE POROSITY IN

WELDS

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5 ACIDS AND ALKALIES

ACIDS AND ALKALIES ARE BOTH ELECTROLYTIC

THEY BOTH DISSOCIATE INTO IONS

FOR EXAMPLE HCl, HYDROCHLORIC ACID H+ and Cl- NaCl, SODIUM CHLORIDE Na+ and Cl-

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6 BI-METALLIC CORROSION

WHEN 2 DIFFERENT METALS ARE IN DIRECT CONTACT

OR, JOINED BY A CONDUCTIVE WIRE IN AN

ENVIRONMENT WHERE AN ELECTROLYTE IS PRESENT,

ONE OF THE METALS WILL CORRODE.

THIS IS DEPENDANT ON THE POSITION IN THE

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BI-METALLIC CORROSION

WHEN THE POTENTIALS OF THE METALS ARE KNOWN, THE LIST CAN ALSO BE KNOWN AS

1 THE ELECTRO-MOTIVE FORCE SERIES

2 THE ELECTRO-CHEMICAL SERIES

BOTH THE POSITION IN THE LIST AND THE FREE POTENTIAL CAN ALTER WITH A DIFFERENT

ELECTROLYTE AND TEMPERATURE

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CORROSION

GALVANIC SERIES

“Electro-motive force series” or the “Electro-Chemical series”

Cathodic end of the table, will not corrode or slow to corrode.

NOBLE

IGNOBLE

Anodic end of the table, will corrode or corrode at a faster rate.

Note and remember the relative positions of:

Mill Scale – Steel – Aluminium - Steel

The above materials are an extract from The Galvanic Series and not the complete list of

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BI-METALLIC CORROSION

ZINC ANODE

MILD STEEL CATHODE

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SURFACE PREPARATION

WHY ?

TO REMOVE CONTAMINANTS IN ORDER TO PROVIDE A

SURFACE TO WHICH THE PAINT WILL READILY

ADHERE

TO PROVIDE A LONGER SERVICE LIFE FROM THE

COATING

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02 FACTORS FOR CONSIDERATION

DEGREE OF CLEANLINESS DEGREE OF ROUGHNESS

OR SURFACE PROFILE

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SURFACE PREPARATION METHODS

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SURFACE PREPARATION BY DRY ABRASIVE BLASTING

ABRASIVES PROFILE AND ADHESION PROFILE MEASUREMENT AND ASSESSMENT RUST GRADES AND DEGREE OF CLEANLINESS

EQUIPMENT

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DRY ABRASIVE BLASTING ABRASIVES METALLIC SHOT

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DRY ABRASIVE BLASTING ABRASIVES

METALLIC GRIT AND

SHOT MIXED RATIO

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DRY ABRASIVE BLASTING ABRASIVES WALNUT SHELL.

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DRY ABRASIVE BLASTING ABRASIVES PARTICLE SIZE DISTRIBUTION, SIEVES TO BS 410

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BLASTING POTS - MACHINES

Blasting Pots and Machines come in many varieties and sizes.

3 points to remember:

A) Blast cleaning is dangerous, so don’t get too close it !

B) Grit exits the nozzles (Venturi) at 450 mph or 720 kph !

C) When the blaster releases the dead man handle the pot will exhaust the air inside very quickly, it is noisy and always

contains particles of grit !!!!!

SAFETY – SAFETY – SAFETY - SAFETY

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MECHANICAL CLEANING TOOLS

Top : Chisel Gun Bottom: Needle Gun

Caution: Both lead to very high surface profile.

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MECHANICAL CLEANING TOOLS

B) Needles always come out of the brushes at high speed due

to use and centrifugal force and they are very dangerous

SAFETY – SAFETY – SAFETY - SAFETY

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SIZING OF ABRASIVES G=GRIT, IRREGULAR SHAPE, SHARP EDGES

S=SHOT,SPHERICAL, WORK HARDENS

VARIOUS SYSTEMS RELATING TO SIZE THE B.S 2451, NOW DEFUNCT, FOR METALLICS.

THE S.A.E, USING THE J 444 SIEVE SYSTEM.

THE BS 7079 Pt E, PARTICLE SIZE DISTRIBUTION

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PROFILE MEASUREMENT SURFACE PROFILE NEEDLE

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SURFACE PROFILE MEASUREMENT, DIAL MICROMETER AND SURFACE REPLICA TAPE

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SURFACE PROFILE MEASUREMENT, DIAL MICROMETER

AND SURFACE REPLICA TAPE

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SURFACE PROFILE MEASUREMENT

SURFACE PROFILE COMPARATOR

PLACE ON SUBSTRATE AND ASSESS THE SUBSTRATE IN COMPARISON TO SEGMENTS.

ENSURE YOU USE CORRECT TYPE

THE 2 TYPES ARE FOR SHOT AND GRIT THE GRIT COMPARATOR MAY BE USED FOR

SHOT/GRIT MIXTURE.

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SURFACE PROFILE ASSESSMENT

SURFACE COMPARATOR TO BS 7079 Pt C, ISO 8503

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RUST GRADES

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RUST GRADES

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BLASTING GRADES A Sa 2.5 and Sa 3

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BLASTING GRADES B Sa 1 and Sa 2

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BLASTING GRADES B Sa 2.5 and Sa 3

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BLASTING GRADES, COMPARISONS

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BLASTING GRADES C Sa 1 and Sa 2

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BLASTING GRADES C Sa 2.5 and Sa 3

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BLASTING GRADES D Sa 1 and Sa 2

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BLASTING GRADES D Sa 2.5 and Sa 3

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EQUIPMENT WHEELABRATERS or CENTRIFUGAL BLAST UNITS

TOTALLY ENCLOSED AUTOMATIC CHAIN DRIVEN ROLLER FEED

VARYING NUMBER OF OPERATING WHEELS

GRAVITY FED ABRASIVE AIRWASH CLEANSING SYSTEM FOR ABRASIVES

PREFERRED ABRASIVE, SHOT

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EQUIPMENT DRY ABRASIVE BLASTING COMPRESSORS, pressure rating in psi capacity in cfm BACK PRESSURE AT NOZZLE, hypodermic needle gauge PRESSURISED BLAST POTS, suitable capacity

VAPOUR TRAPS, knock out pots for removal of oil and water from air stream

CARBON IMPREGNATED HOSES, reduce static shock

NOZZLES, venturi and straight bore

SAFETY TO IGE SR 21

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B.G.A.S PAINT INSPECTION

DRY ABRASIVE BLASTING MEASURING PRESSURE AT THE NOZZLE HYPODERMIC NEEDLE

GAUGE

INSERT THE NEEDLE

THROUGH THE HOSE

WITH THE NEEDLE

TOWARDS THE NOZZLE,

AT AN ANGLE OF APP

45 DEGREES

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EQUIPMENT WET BLASTING HIGH PRESSURE PURE WATER BLASTING, >30,000psi HIGH PRESSURE WATER PLUS ABRASIVE INJECTION LOW PRESSURE WATER PLUS ABRASIVE INJECTION STEAM CLEANING

AIR BLASTING WITH WATER INJECTION

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HAND AND POWER TOOL CLEANING, BS 7079 Pt A

HAND AND POWER WIRE BRUSHES, CHIPPING

HAMMERS, NEEDLE GUNS, EMERY CLOTH, GRINDERS

St 2, THOROUGH HAND AND POWER TOOL CLEANING

St 3, VERY THOROUGH HAND AND POWER TOOL

CLEANING

NO STANDARD FOR RUST GRADE A (because the mill scale is much harder than the bristles on the brushes, which are of non sparking alloys such as phosphor

bronze and beryllium bronze )

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HAND AND POWER TOOL CLEANING B St 2 and St 3

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HAND AND POWER TOOL CLEANING C St 2 and St 3

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SURFACE PREPARATION HAND AND POWER TOOL CLEANING D St 2 and St 3

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PICKLING IS ACID BATH FOLLOWED BY WASHING

FOOTNERS DUPLEX PROCESS IS PICKLING FOLLOWED BY PASSIVATION

:-PROCESS.

PASSIVATION IS TREATMENT IN PHOSPHORIC

OR CHROMIC ACID, AND IS DONE TO PASSIVATE THE STEEL, BY FORMING A LAYER OF RUST- -

INHIBITIVE SALTS WHICH ALSO AID ADHESION

AND PROVIDE RESISTANCE TO CATHODIC

DISBONDMENT

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SURFACE PREPARATION, CHEMICAL CLEANING

AFTER FINAL WASH

FOR B Gas THE

FIGURE SHOULD BE

BETWEEN 4.5 and 7

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TESTS FOR SURFACE CONTAMINANTS

HYGROSCOPIC SALTS :- POTASSIUM FERRICYANIDE, NOW CALLED POTASSIUM HEXACYANOFERRATE

SOLUBLE CHLORIDES :- SILVER NITRATE TEST

MILLSCALE :- COPPER SULPHATE

OIL OR GREASE :- SOLVENT OTHER THAN ALIPHATIC MOISTURE :- TALCUM OR CHALK

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QUANTITITIVE TESTS FOR HYGROSCOPIC SALTS

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BGAS PAINTING INSPECTION

SALTS DETECTION, BRESLE SAMPLE PATCH KIT

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PAINT TECHNOLOGY

3 MAIN GROUPS OF PAINT.

1 PAINTS CONTAINING SOLVENTS

2 SOLVENT FREE MULTI-PACK, MCL’s

3 POWDER PAINTS

ALL HAVE THE SAME BASIC INGREDIENTS

BINDER SOLVENT PIGMENTS AND OTHER ADDITIVES

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PAINTS CONTAINING SOLVENTS

This group is still the largest in terms of sales

It is important to realise that solvent does not

relate solely to Hydrocarbon solvents, but also includes water

Due to the modern EPA (Environmental Protection Act) requirements, manufacturers are

researching into new paint technology involving vastly reduced amounts of volatile organic

compounds

Some are using water -based technology, some are concentrating on the solvent free materials

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SOLVENT FREE MULTI-PACK, MCL’s

As the name implies these materials contain

no (or in some cases a minute amount of) solvent

These are generally chemical curing

materials which require the mixing of two

or more components and usually go under the name of M.C.L’s s (Multi Component

Liquids)

Some MCLs MCLs are made using solvent borne

materials.

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In theory every particle contains all necessary

ingredients to effect a cure into a protective film The powder can be applied onto a preheated substrate (in the case of substantial steel thicknesses) at about

240oc, or onto thin plate electro statically, and post heated In either case the powder melts, undergoes a chemical reaction and in approximately three minutes the reaction is complete.

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B.G.A.S PAINT INSPECTION

BINDERS PROPERTIES REQUIRED EASE OF APPLICATION

TO GIVE ADHESION TO THE SUBSTRATE

TO PROVIDE RESISTANCE TO ABRASION

TO PROVIDE CHEMICAL RESISTANCE

TO PROVIDE COHESIVE STRENGTH

TO PROVIDE DIALECTRIC STRENGTH

TO RESIST THE PASSAGE OF WATER

TO CHANGE FROM A LIQUID INTO A SOLID

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natural oils and resins phenolic resins

styrene and vinyl

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Solvents are added to paints to reduce the viscosity and ease application properties.

The solvents used in paints have to fulfil

various other requirements, for example if

a solvent evaporates away too quickly the film will not dry evenly, if it evaporates too slowly drying will be protracted and on

vertical surfaces the paint is likely to sag.

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SOLVENTS COMPATIBILITY CORRECT SOLVENT GROUP FOR BINDER COMPATABILITY FOR OVERCOATING FLASHPOINT AND TOXICITY CONSIDERATIONS

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SOLVENTS STRONG SOLVENTS FOR STRONG BINDERS

WEAKER SOLVENTS FOR WEAKER BINDERS

THE STRONGER SOLVENTS HAVE A LOW NUMBER

OF CARBON ATOMS IN THE CHEMICAL FORMULA

THE HIGHER THE NUMBER OF CARBON ATOMS,

THE HIGHER THE BOILING POINT OF THE

SOLVENT

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POLYMERS

A STRING OR STRUCTURE OF REPEATED UNITS

LINEAR POLYMER PRE FORMED, REVERSIBLE, VERY

SENSITIVE TO SOME HC SOLVENTS

BRANCHED POLYMER OXIDATION DRYING,

NATURAL OILS AND RESINS , BECOME VERY BRITTLE.

CROSSLINKED POLYMER CHEMICALLY CURING, VERY STRONG, EPOXIES, URETHANES AND POLYURETHANES

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RESINS

Natural resins are from the main plant, e.g a tree trunk Resins are brittle by nature and dry very

quickly and as such, need modification This

modification is by way of addition of oils.

Natural resins are Copals and Dammars and

Coumarones, Amber and Laq Other resins such as frankincense and myrrh are more valued for their perfume qualities.

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OILS DRYING OILS Three sets of double bonds along a

carbon backbone, react readily in ambient conditions carbon backbone, react readily in ambient conditions

SEMI-DRYING OILS One or two sets of double

bonds, not quite as reactive as drying oils Need a

catalyst such as heat to start the polymerisation

NONE-DRYING OILS Cannot be used as binders, will not polymerise, no activity points Are used as

plasticisers, to give flexibility and ease application.

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PIGMENTS GENERALLY ANIMAL, VEGETABLE, MINERAL, OR SYNTHETIC PARTICLE SIZE VARIES FROM 1/ 1/

10

10 th MICRON to AVERAGE SIZE OF 1 MICRON

PIGMENTS CONTRIBUTE TO COHESIVE STRENGTH, ABRASION RESISTANCE, DURABILITY, OPACITY

AND IN SOME INSTANCES, IMPERMEABILITY, AND RESISTANCE TO U/V RAYS.

PIGMENTS MUCH NOT DISSOLVE IN THE VEHICLE

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PIGMENTS ANTI-CORROSIVE :- RUST INHIBITIVE PROPERTIES METALLIC :- WORK SACRIFICIALLY

OPAQUE :- INERT, PROVIDE OPACITY AND COLOUR EXTENDERS :- ADD BULK, REDUCE COST

LAMINAR :- PROVIDE IMPERMEABILITY

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BGAS PAINTING INSPECTION

MIO LAMINAR PIGMENTS

ATTRIBUTES OF MIO RETARDS PERMEATION

UV A and B REFLECTION DURABILITY

ADHESION TO NEXT LAYER

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LAMINAR PIGMENTS EG MIO

DELAMINATED MIO

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TOXICITY, SAFETY LEVELS OF EXPOSURE

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OTHER ADDITIVES ANTI-SETTLING AGENTS, AIDS TO SHELF LIFE

PLASTICISERS, REDUCE BRITTLENESS, AID

APPLICATION AND PROVIDES FLEXIBILITY

DRIERS, ALLOW EVEN THROUGH DRYING OF

OXIDISING FILMS ANTI-SKINNING AGENTS, RETARD THE

FORMATION OF SURFACE SKINS

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SOLUTIONS AND DISPERSIONS SOLVENT:- Will dissolve another material.

solute in a solvent

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SOLUTIONS AND DISPERSIONS

WITHIN ANOTHER LIQUID, WHERE THERE IS NO SOLUBILITY

DISPERSED WITHIN A LIQUID, NO SOLUBILITY

ANOTHER LIQUID WHERE THERE IS

NO SOLUBILITY

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DRYING AND CURING OF PAINT FILMS

SOLVENT EVAPORATION

NO CHEMICAL REACTION POLYMERS ARE PREFORMED AND SATURATED LINEAR POLYMERS CLOSED AT THE ENDS BY HYDROGEN AND HAVE NO DOUBLE BONDS

ALSO CALLED REVERSIBLE OR NON-

CONVERTIBLE

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OXIDATION USES ATMOSPHERIC OXYGEN OXYGEN CHEMICALLY COMBINES WITH

UNSATURATED DOUBLE BONDS PROCESS CAN BE ACCELERATED BY ADDITION OF

DRIERS ALSO CALLED CONVERTIBLE OR NON-REVERSIBLE

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CHEMICAL CURING

MUST BE MIXED IN THE CORRECT RATIO POT LIFE AND INDUCTION PERIOD MUST BE

OBSERVED CONVERTIBLE OR NON-REVERSIBLE

CHEMICALLY CROSS LINK

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COALESCENCE

PENETRATE SPHERES

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