B.G.A.S. PAINTING INSPECTION
B.G.A.S. PAINTING INSPECTION
WELCOME
LEVEL 2/3
COURSE TUTOR
TREVOR MYERS
B.G.A.S. PAINTING INSPECTION
B.G.A.S. PAINTING INSPECTION
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
B.G.A.S. PAINTING INSPECTION
B.G.A.S. PAINTING INSPECTION
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
B.G.A.S PAINTING INSPECTION
B.G.A.S PAINTING INSPECTION
CORROSION THEORY
CORROSION THEORY

B.G.A.S PAINTING INSPECTION
B.G.A.S PAINTING INSPECTION
CORROSION THEORY
CORROSION THEORY
B.G.A.S. PAINTING INSPECTION
B.G.A.S. PAINTING INSPECTION
CORROSION THEORY
THE CORROSION TRIANGLE
ANODE
CATHODE
ELECTROLYTE
Shows electrical circuit
B.G.A.S. PAINTING INSPECTION
B.G.A.S. PAINTING INSPECTION
CORROSION THEORY
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
B.G.A.S PAINTING INSPECTION
B.G.A.S PAINTING INSPECTION
FACTORS ACCELERATING CORROSION
FACTORS ACCELERATING CORROSION
1. TEMPERATURE, THERMODYNAMICALLY UNSTABLE
1. TEMPERATURE, THERMODYNAMICALLY UNSTABLE
AS THE STEEL HEATS UP, IT GAINS MOLECULAR
AS THE STEEL HEATS UP, IT GAINS MOLECULAR

FREEDOM, BECOMES MORE ACTIVE, AND
FREEDOM, BECOMES MORE ACTIVE, AND
UNDERGOES CORROSION MORE READILY
UNDERGOES CORROSION MORE READILY
B.G.A.S. PAINTING INSPECTION
B.G.A.S. PAINTING INSPECTION
FACTORS ACCELERATING CORROSION
FACTORS ACCELERATING CORROSION
2. HYGROSCOPIC (OSMOTIC) BLISTERS
2. HYGROSCOPIC (OSMOTIC) BLISTERS
TINY, PIN HEAD
TINY, PIN HEAD
SIZE, WATER
SIZE, WATER
FILLED BLISTERS.
FILLED BLISTERS.
CAUSED BY
CAUSED BY
HYGROSCOPIC
HYGROSCOPIC
SALTS
SALTS
B.G.A.S. PAINTING INSPECTION
B.G.A.S. PAINTING INSPECTION
FACTORS INFLUENCING CORROSION
FACTORS INFLUENCING CORROSION
3. AEROBIC CONDITIONS, PRESENCE OF OXYGEN
3. AEROBIC CONDITIONS, PRESENCE OF OXYGEN
INTRODUCE OXYGEN, DOUBLE THE IONS
INTRODUCE OXYGEN, DOUBLE THE IONS

2H
2H
2
2
O+O
O+O
2
2
+ 4e = 4OH
+ 4e = 4OH
-
-
TWICE THE NUMBER OF HYDROXYL IONS
TWICE THE NUMBER OF HYDROXYL IONS
WILL PASSIVATE TWICE THE NUMBER OF
WILL PASSIVATE TWICE THE NUMBER OF
IRON IONS AT THE ANODE
IRON IONS AT THE ANODE
B.G.A.S PAINTING INSPECTION
B.G.A.S PAINTING INSPECTION
FACTORS INFLUENCING CORROSION
FACTORS INFLUENCING CORROSION
4. PRESENCE OF SOME BACTERIA ON THE SURFACE
4. PRESENCE OF SOME BACTERIA ON THE SURFACE
S.R.B
S.R.B
’
’
s SULPHUR REDUCING BACTERIA
s SULPHUR REDUCING BACTERIA

M.E.M
M.E.M
’
’
s METAL EATING MICROBES
s METAL EATING MICROBES
USUALLY SMALL HOLES WHICH FOLLOW THE
USUALLY SMALL HOLES WHICH FOLLOW THE
DIRECTION OF GRAVITY, NOT UNLIKE POROSITY IN
DIRECTION OF GRAVITY, NOT UNLIKE POROSITY IN
WELDS
WELDS
B.G.A.S PAINTING INSPECTION
B.G.A.S PAINTING INSPECTION
FACTORS INFLUENCING CORROSION
FACTORS INFLUENCING CORROSION
5. ACIDS AND ALKALIES
5. ACIDS AND ALKALIES
ACIDS AND ALKALIES ARE BOTH ELECTROLYTIC
ACIDS AND ALKALIES ARE BOTH ELECTROLYTIC
THEY BOTH DISSOCIATE INTO IONS
THEY BOTH DISSOCIATE INTO IONS
FOR EXAMPLE
FOR EXAMPLE
HCl, HYDROCHLORIC ACID H+ and Cl
HCl, HYDROCHLORIC ACID H+ and Cl
-
-
NaCl, SODIUM CHLORIDE Na+ and Cl
NaCl, SODIUM CHLORIDE Na+ and Cl

-
-
B.G.A.S. PAINTING INSPECTION
B.G.A.S. PAINTING INSPECTION
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
GALVANIC LIST
THE POSITION IN THE LIST DETERMINES WHICH
METAL BECOMES THE ANODE, THE DISTANCE
BETWEEN THEM DETERMINES THE POTENTIAL
B.G.A.S PAINTING INSPECTION
B.G.A.S PAINTING INSPECTION
BI
BI
-
-
METALLIC CORROSION
METALLIC CORROSION
WHEN THE POTENTIALS OF THE METALS ARE
WHEN THE POTENTIALS OF THE METALS ARE
KNOWN, THE LIST CAN ALSO BE KNOWN AS .
KNOWN, THE LIST CAN ALSO BE KNOWN AS .
1. THE ELECTRO
1. THE ELECTRO
-
-

MOTIVE FORCE SERIES
MOTIVE FORCE SERIES
2. THE ELECTRO
2. THE ELECTRO
-
-
CHEMICAL SERIES
CHEMICAL SERIES
BOTH THE POSITION IN THE LIST AND THE FREE
BOTH THE POSITION IN THE LIST AND THE FREE
POTENTIAL CAN ALTER WITH A DIFFERENT
POTENTIAL CAN ALTER WITH A DIFFERENT
ELECTROLYTE AND TEMPERATURE
ELECTROLYTE AND TEMPERATURE
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
materials.
MATERIAL KNOWN POTENTIAL AV. VALUES
Graphite + 0.25 v
Titanium 0.0 v
Silver - 0.1 v
Nickel 200 - 0.15 v
Lead - 0.2 v
Admiralty Brass - 0.3 v
Copper - 0.35 v
Tin - 0.35 v
Mill Scale - 0.4 v
Low Alloy Steel - 0.7 v
Mild Steel - 0.7 v
Aluminium Alloys - 0.9 v
Zinc - 1.0 v
Magnesium - 1.6 v
B.G.A.S. PAINTING INSPECTION
B.G.A.S. PAINTING INSPECTION
BI-METALLIC CORROSION
ZINC ANODE
MILD STEEL
CATHODE
B.G.A.S. PAINTING INSPECTION
B.G.A.S. PAINTING INSPECTION
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
B.G.A.S. PAINTING INSPECTION
B.G.A.S. PAINTING INSPECTION
02 FACTORS FOR CONSIDERATION
DEGREE OF CLEANLINESS
DEGREE OF ROUGHNESS
OR SURFACE PROFILE
B.G.A.S. PAINTING INSPECTION
B.G.A.S. PAINTING INSPECTION
SURFACE PREPARATION METHODS
•
DRY ABRASIVE BLAST CLEANING
•
WET BLASTING
•
HAND AND POWER TOOL CLEANING
•
FLAME CLEANING
•
PICKLING (CHEMICAL CLEANING)
•
VAPOUR DEGREASING
•
WEATHERING
B.G.A.S. PAINTING INSPECTION

B.G.A.S. PAINTING INSPECTION
SURFACE PREPARATION BY DRY ABRASIVE BLASTING
ABRASIVES
PROFILE AND ADHESION
PROFILE MEASUREMENT AND ASSESSMENT
RUST GRADES AND DEGREE OF CLEANLINESS
EQUIPMENT
B.G.A.S. PAINTING INSPECTION
B.G.A.S. PAINTING INSPECTION
SURFACE PREPARATION
DRY ABRASIVE BLASTING ABRASIVES
COPPER SLAG.
EXPENDABLE. USE
ONCE ONLY, IT
SHATTERS ON
IMPACT. IT IS
NON METALLIC
B.G.A.S. PAINTING INSPECTION
B.G.A.S. PAINTING INSPECTION
SURFACE PREPARATION
DRY ABRASIVE BLASTING, ABRASIVES
CONTAMINATED
COPPER SLAG.
MUST NOT BE RE-
USED.
B.G.A.S. PAINTING INSPECTION
B.G.A.S. PAINTING INSPECTION
SURFACE PREPARATION
DRY ABRASIVE BLASTING, ABRASIVES
GARNET. MINERAL,

CAN BE EXPENDABLE
OR CAN BE RE-
CYCLED , AS
DESIRED. MUST BE
CLEANSED BEFORE
RE-USE
B.G.A.S. PAINTING INSPECTION
B.G.A.S. PAINTING INSPECTION
SURFACE PREPARATION
DRY ABRASIVE BLASTING ABRASIVES
METALLIC GRIT.
MUST BE RECYCLED
FOR ECONOMIC
REASONS. NOT
USED FOR SITE
WORK MUST BE
CLEANSED BEFORE
RE-USE
B.G.A.S. PAINTING INSPECTION
B.G.A.S. PAINTING INSPECTION
DRY ABRASIVE BLASTING ABRASIVES
METALLIC SHOT
USED IN
ENCLOSED
SYSTEMS, NEEDS
TO BE CLEANSED
BEFORE RE-USE.
GRADUALLY
WEARS DOWN
CYCLE BY CYCLE.