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Nimbus Technical Training Institute delivers hands-on, internationally recognised certifications in welding inspection, NDT, painting inspection, safety, and API standards — shaping industry-ready professionals since 2010.

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API 571 Preparation Course

Build a strong understanding of corrosion, materials, and damage mechanisms affecting fixed equipment in industrial service.

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API 577 Preparation Course

Develop essential knowledge of welding inspection, welding processes, metallurgy, and common weld defects.

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API 580 Preparation Course

Learn the principles of Risk-Based Inspection and how to apply RBI methods for safer and more efficient asset management.

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API 936 Preparation Course

Gain specialized knowledge in refractory installation quality control, inspection practices, and material qualification requirements.

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API 510 Preparation Course

Understand the core requirements of in-service pressure vessel inspection, damage assessment, and repair decisions.

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API 570 Preparation Course

Build a strong foundation in piping inspection, piping design principles, and in-service damage assessment.

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API 653 Preparation Course

Learn the principles of aboveground storage tank inspection, repair, alteration, and integrity assessment.

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API SIEE Preparation Course

Gain practical understanding of source inspection requirements for electrical equipment and vendor quality surveillance.

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API SIFE Preparation Course

Develop the knowledge required for source inspection of fixed equipment used in petroleum and petrochemical industries.

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In-House & Customised Training for Organisations

We develop and deliver bespoke training programmes tailored to your organisation’s specific requirements — at your facility or ours. Ideal for oil & gas, construction, and manufacturing companies seeking to upskill teams efficiently.

Welcome to your TIG Welding

Name

TIG welding is also called:

Gas tungsten arc welding (GTAW)

Manual metal arc welding (MMA)

Shielded metal arc welding (SMAW)

Gas metal arc welding (GMAW)

In TIG welding, the electrode is:

Consumable

Non-consumable tungsten

Flux coated

Coated with cellulose

The purpose of inert shielding gas in TIG welding is to:

Increase weld penetration

Cool the weld pool

Prevent oxidation and contamination

Reduce current requirements

Tungsten is used because it has a melting point of approximately:

1500°C

2500°C

3370°C

4000°C

Main TIG welding process variables include:

Electrode coating only

Current type only

Welding current, current type/polarity, travel speed, electrode tip, gas flow, extension

Gas type only

Low welding current in TIG can cause:

Overheating of tungsten

Unstable arc

Excess penetration

Wider bead

High welding current in TIG can result in:

Cold lap

Tungsten melting and inclusions

Narrow bead

Inadequate fusion

. Best TIG welding results are usually obtained with:

AC only

DC+ve

DC-ve

Pulsed current only

AC or DC+ve polarity is preferred for:

Low penetration

DC-ve only

Welding refractory oxides such as aluminium or magnesium

All metals equally

10.

DC+ve polarity concentrates heat:

At the workpiece

At the electrode tip

Equally on electrode and workpiece

At the filler wire

11.

DC-ve polarity distributes heat:

70% at workpiece, 30% at electrode

50% at workpiece, 50% at electrode

30% at workpiece, 70% at electrode

Equally at all positions

12.

AC polarity distributes heat:

70% at workpiece, 30% at electrode

50% at workpiece, 50% at electrode

30% at workpiece, 70% at electrode

Only at electrode

13.

TIG welding penetration increases when:

) Travel speed increases

Vertex angle increases

Vertex angle decreases

Shielding gas decreases

14.

TIG electrode extension (stickout) should generally be:

1× electrode diameter

2–3× electrode diameter

4× electrode diameter

Any length

15.

Too short electrode extension can cause:

Low penetration

Unstable arc

Excess filler deposition

Wider bead

16.

. Too long electrode extension can result in:

Low arc stability

Reduced penetration

Overheating and tungsten inclusions

Proper fusion

17.

Typical TIG shielding gases include:

Argon, helium, or mixtures of both

Oxygen and CO₂

Nitrogen and hydrogen only

CO₂ only

18.

Adding ~5% hydrogen to argon is used for:

Copper welding only

Austenitic stainless steel to improve penetration and reduce porosity

Aluminium welding only

Magnesium welding only

19.

. Helium shielding gas is advantageous for:

) Thin sections only

Thick materials due to higher arc heat

Low melting metals

All welds equally

20.

Argon shielding gas is preferred for:

Thin sections due to better draught resistance

High melting metals ony

Thick plates

Non-metallic materials

21.

Typical TIG shielding gas flow rate is approximately:

2–4 l/min

10–12 l/min

15–20 l/min

20–25 l/min

22.

Too low shielding gas flow can cause:

Excess heat

Slag inclusions

Porosity and contamination

Arc blow

23.

Too high shielding gas flow can cause:

Reduced penetration

Turbulence and air entrainment leading to porosity

Narrow bead

Stable arc

24.

Back purging in TIG welding is done to:

Clean filler wire

Prevent oxidation on the back side of the weld

Reduce arc voltage

) Increase travel speed

25.

. Typical back purge gas is:

Pure argon

Helium

P CO₂

Nitrogen

26.

For plate welding back purge may require:

Only one operator

Purge channel or moving nozzle

No gas

AC polarity

27.

Electrode tip shapes for DC-ve TIG welding are usually:

Sharpened/thoriated, ceriated, lanthaniated with vertex angle

Flat

Hemispherical only

Rounded for AC

28.

Electrode tip shape for AC TIG welding is:

Sharpened

Balled or flat to prevent breakage

Sharpened for DC+ve

Pointed only

29.

30.

Pure or zirconiated tungsten electrodes are mainly used for:

DC-ve only

AC welding with balled tip

DC+ve only

Pulsed welding only

31.

Filler wires in TIG welding:

Must always be identical to base metal

Usually similar in composition with small additions to control O/N

Made of tungsten

Only aluminium alloys

32.

Tungsten inclusions occur due to:

Incorrect gas

Thermal shock to tungsten or electrode overheating

Incorrect travel speed only

Argon purity

33.

Modern TIG power sources use current slope-up to:

Reduce penetration

Heat tungsten slowly and avoid inclusions

Increase arc voltage rapidly

Minimize electrode extension

34.

Crater cracking is avoided using:

AC current

Pure argon

Current slope-out to reduce weld pool gradually

Thoriated electrodes

35.

TIG welding common applications include:

Thick plate MMA welding only

Thin walled pipes, tubing, aerospace components

Field MIG welding only

Heavy steel beams only

36.

TIG is particularly suitable for:

Low quality joints

Steel only

High quality welds with low hydrogen

Unshielded welding

37.

Advantages of TIG welding include:

High deposition rate

No shielding required

Clean welds, controlled variables, suitable for thin metals

No skill needed

38.

Disadvantages of TIG welding include:

High deposition

Easy for beginners

Low deposition, higher dexterity required, less economical on thick metals

Slag inclusions

39.

TIG welding produces welds with:

High spatter

No spatter or slag inclusions

High hydrogen only

Slag covering

40.

Welding reactive metals with stable oxides such as aluminium requires:

AC with filler

TIG for controlled variables and clean welds

MIG only

DC+ve only

41.

TIG welding can be performed:

Only in flat position

Only vertical

On thin sections with or without filler metal

Only for steel

42.

Electrode grinding dust from thoriated tungsten is:

Harmless

Radioactive, requires dust extraction

Only chemical hazard

Only AC welding hazard

43.

Ceriated and lanthaniated electrodes:

Only for AC

Radioactive

Operate with AC/DC, non-radioactive alternatives to thoriated

Low current only

44.

Zirconiated electrodes:

Cannot retain balled end

Only for DC

Retain balled end, high resistance to contamination, recommended for AC

Poor arc stability

45.

Increasing travel speed in TIG welding:

Increases penetration

Reduces penetration and weld width

Increases bead width only

Improves cleaning

46.

Reducing travel speed in TIG welding:

Increases penetration and weld width

Decreases bead width

Reduces heat input

Increases arc voltage

47.

TIG welding is particularly used in:

Low integrity joints

Chemical, petroleum, aerospace industries

Only for MMA replacement

Only low carbon steels

48.

AC TIG welding is used to weld:

Steels only

Aluminium and magnesium (removes oxides)

Stainless steels only

Titanium only

49.

Electrode tip angle for DC TIG should be:

30°–45°

2–2.5× electrode diameter length for sharpened tip

90°

Rounded only

50.

AC electrode tip is typically:

Sharpened

Flat to minimise breakage

Pointed for penetration

Rounded for DC

51.

Shielding gas lighter than air requiring more flow is:

Argon

Helium

Oxygen

CO₂

52.

Shielding gas heavier than air and more draught resistant is:

Argon

Helium

Nitrogen

CO₂

53.

In TIG, small tungsten fragments in weld are:

Acceptable

Not acceptable, detected on radiographs

Only cosmetic

Improve penetration

54.

Filler metal additions in TIG welding are used to:

Increase arc voltage

Combine with oxygen/nitrogen in weld

Reduce current

Only for AC welding

55.

. TIG welding is less economical than MMA/MIG for:

Thin sections

Sections thicker than ~10mm

Reactive metals

Stainless steels

56.

TIG welding requires:

Low skill only

High dexterity and coordination

No shielding

Only DC current

57.

Pure tungsten electrodes are preferred for:

AC welding of light metals

DC-ve only

Reactive metals only

High deposition

58.

Thoriated electrodes are:

Non-radioactive

Radioactive, improved arc initiation, sharp tip retention

Only for AC

Poor arc stability

59.

Ceriated electrodes can be used with

DC only

AC or DC, non-radioactive

AC only

Low current only

60.

Zirconiated electrodes are resistant to:

High current

Contamination, ideal for high integrity welds

AC only

Radioactivity

61.

Small tungsten inclusions occur primarily due to:

High shielding gas

Thermal shock or electrode overheating

Low travel speed

Filler wire contamination

62.

Current slope-up in TIG welding helps to:

Increase travel speed

Minimise tungsten inclusions by gradual heating

Reduce arc voltage

Increase bead width

63.

Current slope-out in TIG welding is used to:

Increase penetration

Reduce electrode wear

Avoid crater cracking at weld termination

Cool the torch

64.

Crater cracking occurs due to:

High shielding gas

Excessive filler metal

Solidification stress in the weld pool

AC welding only

65.

Autogenous TIG welding refers to:

Welding with filler metal

Welding without filler metal

AC welding only

DC+ve welding only

66.

For stainless steel pipes, TIG welding is often used:

Only on thick plates

For thin-walled longitudinal seams

For aluminium only

For cast iron only

67.

TIG welding in aerospace is used for:

Only steel components

Airframes and rocket motor cases

Only aluminum pipes

Heavy castings only

68.

Advantages of TIG welding include:

High deposition rate

Low diffusible hydrogen, clean welds, high control

No skill requirement

Works only on ferrous metals

69.

TIG welding is particularly useful for:

Thick plates above 50mm

Steel only

Reactive metals with stable oxides

High spatter applications

70.

Disadvantages of TIG welding include:

Low deposition rate, requires high skill, less economical on thick sections

Produces spatter

Requires no shielding gas

Can’t weld thin metals

71.

In TIG welding, the filler metal is:

Always non-metallic

Usually similar to parent metal with minor alloying

Tungsten

AC only

72.

High welding current in TIG can result in:

Cold lap

Overheating of tungsten and inclusions

Poor shielding

Low penetration

73.

Low welding current in TIG may cause:

Tungsten melting

Unstable arc and poor penetration

Wide bead

Excess spatter

74.

Electrode extension is measured from:

Gas nozzle tip

Contact tube to tungsten tip

Filler wire start

Arc length only

75.

Tungsten electrode tip length for DC welding is usually:

Equal to diameter

2–2.5 times the electrode diameter

4× diameter

1/2× diameter

76.

Electrode tip for AC welding is:

Sharpened

Flat or balled to prevent breakage

Pointed only

Not critical

77.

Travel speed in TIG welding affects:

Only penetration

Both penetration and weld width

Only electrode wear

Only arc stability

78.

Increasing travel speed in TIG welding:

Increases penetration

Reduces penetration and width

Increases bead height

Reduces heat input only

79.

Reducing travel speed in TIG welding:

Increases penetration and weld width

Reduces penetration

Reduces bead size

Increases electrode wear

80.

Helium shielding gas is best for:

Thin metals

Thick sections due to higher arc heat

All metals equally

Low melting metals only

81.

Argon shielding gas is preferred for:

Thin sections due to draught resistance and heavier gas

Thick sections only

High melting metals only

AC only

82.

Shielding gas flow too low results in:

Arc wander

Electrode overheating

Porosity and weld contamination

Cold lap

83.

Shielding gas flow too high causes:

Low heat input

Turbulence and air entrainment causing porosity

Low bead width

Over-penetration

84.

Back purging is critical for:

Aluminium welding only

Preventing oxidation on weld backside

DC+ve welding only

AC welding only

85.

Typical back purge gas is:

Argon

Helium

Nitrogen

CO₂

86.

Back purge flow rate should be reduced prior to welding to:

Increase bead width

Ensure positive flow without turbulence

Increase penetration

Reduce electrode wear

87.

Filler wires in TIG welding

Must be identical to tungsten

Similar to parent metal with minor additions

AC only

) Pure tungsten

88.

Thermal shock in tungsten can lead to:

AC welding

Tungsten inclusions in weld

Reduced shielding gas

Low penetration

89.

Crater cracking is a form of:

Porosity

Solidification cracking

Slag inclusion

Undercut

90.

Modern TIG power sources have slope-up devices to:

Increase electrode burn-off

Minimise thermal shock to tungsten

I Reduce shielding gas

Increase arc voltage

91.

. Slope-out devices in TIG welding are used to:

Reduce current gradually at weld end

Increase current

Reduce travel speed

Harden weld pool

92.

Electrode type for AC welding of aluminium is usually:

Thoriated DC

Pure or zirconiated balled end

Ceriated sharpened

Lanthaniated only

93.

Electrode type for DC-ve welding is usually:

Thoriated, ceriated, or lanthaniated sharpened tip

Pure balled end

Zirconiated AC only

Tungsten oxide coated

94.

TIG welding is suitable for:

Only ferrous metals

Almost all weldable metals including dissimilar metals

Only aluminium

Only thin stainless steel

95.

Advantages of TIG welding include:

High deposition only

Superior quality, low hydrogen, accurate control, minimal contamination

No skill required

Low cost for all metals

96.

TIG welding is particularly used in industries requiring:

Low quality joints

High cleanliness such as food, semiconductors, aerospace

Heavy structural welding

Only site welding

97.

Disadvantages of TIG welding include:

High deposition

Low deposition, high skill requirement, less economical for thick sections

Slag inclusions

Low quality welds

98.

Tungsten electrode dust hazard is primarily from:

Argon flow

Grinding thoriated electrodes

AC welding only

DC-ve welding only

99.

TIG welding filler metal additions are used to:

Reduce arc voltage

React with oxygen and nitrogen in weld

Reduce penetration

Increase arc length

100.

TIG welding filler metal additions are used to:

Reduce arc voltage

React with oxygen and nitrogen in weld

Reduce penetration

Increase arc length

101.

Electrode diameter and tip grinding affect:

Only arc voltage

Arc stability, penetration, and bead shape

Gas flow

Only AC welding

102.

Overall, TIG welding is most suited for:

Fast low quality welds

High quality, precise, clean welds on thin or reactive metals

Heavy fabrication only

MMA replacement for field welds

103.

One disadvantage of TIG welding is:

Low deposition rates compared with other arc welding processes

High deposition rates

Produces excessive spatter

Requires no shielding gas

104.

TIG welding requires:

Low skill

Higher dexterity and welder coordination than MIG/MAG or MMA

No training

Only AC current

105.

TIG welding is less economical than MMA or MIG/MAG for:

Thin sections

Sections thicker than ~10mm

Aluminium only

106.

TIG welding may be unsuitable for:

Indoor shop welding

Site/field welding in draughty conditions

Stainless steel only

Reactive metals only

107.

A common issue in TIG welding if the electrode contacts the weld pool is:

Porosity

Undercut

Tungsten inclusions

Cold lap

108.

TIG welding has low tolerance for:

Arc length variations

Travel speed changes

Contaminants on filler or base metals

Electrode tip angle

109.

The shielding of the weld zone in draughty conditions is:

Easier than MMA

Difficult, making TIG less suitable for field work

Not required

Only needed for AC welding

110.

Compared with MIG/MAG or MMA, TIG welding:

Is faster

Produces higher deposition

Requires more skill and coordination

Needs no shielding gas

111.

The risk of tungsten inclusions occurs when:

Electrode touches the weld pool

Travel speed is too fast

Gas flow is too high

Arc voltage is too low

112.

. A limitation of TIG welding is:

Produces slag inclusions

Cannot weld thin metals

No cleaning action, so contaminants affect weld quality

Only works with AC current

113.

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