Protective Coatings

Question 1

Why is the hull painted?

Answer 1

• To provide a smooth finish, reducing drag
• Prevent marine growth
• Anti corrosion barrier to prevent oxygen contacting the hull
• Barrier against galvanic corrosion

Question 2

List some substances that can be considered contaminant when applying a coating?

Answer 2

• Moisture
• Water
• Oil
• Grease
• Dust and dirt
• Weld spatter
• White rust

Question 3

List the advantages and disadvantages of abrasive blasting?

Answer 3

Abrasive blasting advantages
- Can be used to clean large areas of steel.
- Gives a good profile to steel before painting.
- Removes rust, old paint, some oils, grease & soluble salts.

Abrasive blasting disadvantages
- Environmentally unfriendly – noisy, dirty, produces large quantities of dust.
- Can leave retained grit in the steel which is not fully over coated. The grit breaks down early in service giving the appearance of a poor coating performance.

Question 4

List the advantages and disadvantages of Hydroblasting?

Answer 4

Advantages of hydroblasting are:
- Removes soluble salts from the steel surface.
- Water as a cleaning material is generally inexpensive and available in large quantities.
- Lack of contamination of surrounding areas because there are no abrasive particles.
- Lack of dust.

Disadvantages of hydroblasting are:
- No surface profile is produced. It relies on the original profile, if present.
- Flash rusting may be a problem in humid environments.
- The areas behind angles require particular attention as they are difficult to clean
by hydroblasting.

Question 5

What is the AFS Convention?

Answer 5

International Convention on the Control of Harmful Antifouling Systems on Ships (AFS Convention).

Question 6

What is TBT and why is TBT Banned?

Answer 6

Tributyltin (TBT) is an active ingredient in certain antifouling paints used on ships and is one of the most dangerous substances ever deliberately introduced into the marine environment.

Question 7

What does the Anti-fouling system certificate include?

Answer 7

For any vessel over 400gt needs this certificate. It covers;
- Type of antifoam
- Date of application
- Name of company/ location where applied
- Name of manufacture
- Name and colour of Antifoul
- Ingredients and the Chemical Abstract Service Registry Number
- Type of sealer coat
- Colour of sealer coat
- Date of application of sealer coat