Learning Objectives ˗ Specification Components ˗ Consideration of Variables

Abrasive Blast Cleaning Standards SSPC-SP 7/NACE 4 * SSPC-SP 14/NACE 8 * SSPC-SP 6/NACE 3 * SSPC-SP 10/NACE 2 * SSPC-SP 5/NACE 1 * SSPC-SP 16 * In addition, Wet Abrasive Blast (WAB) Standards have been developed.

SSPC-SP10/NACE No. 2, Near-White Blast Cleaning Requires removal of all loosely and tightly adhering mill scale, rust and paint from the surface Staining from rust, paint and mill scale permitted but must not exceed 5% of each 9 square inches of prepared surface

Rust-Back occurs when freshly cleaned steel is exposed to moisture, contamination, or a corrosive atmosphere. The time interval between blast cleaning and rust-back varies greatly from one environment to another. Under mild ambient conditions, if chemical contamination is not present, it is best to blast clean and coat a surface on the same day. Severe conditions may require a more expeditions coating application to avoid contamination from fallout. Chemical contamination should be removed prior to coating. SSPC SP10

Flash Rust is an oxidation product that forms as a wetted carbon steel substrate dries. Flash rust is an additional consideration when a carbon steel substrate is subjected to WAB cleaning. No flash rust: A carbon steel surface that, when viewed without magnification, exhibits no visible flash rust. Light (L) flash rusted surface: A carbon steel surface that, when viewed without magnification, exhibits small quantities of a rust layer through which the carbon steel substrate may be observed. The rust or discoloration may be evenly distributed or present in patches, but it is tightly adherent and not easily removed by lightly wiping with a cloth. Moderate (M) flash rusted surface: A carbon steel surface that, when viewed without magnification, exhibits a layer or rust that obscures the original carbon steel surface. The rust layer may be evenly distributed or present in patches, but it is reasonably well adherent and leaves light marks on a cloth that is lightly wiped over the surface. Heavy (H) flash rusted surface: A carbon steel surface that, when viewed without magnification, exhibits a layer of heavy rust that hides the original carbon steel surface completely. The rust may be evenly distributed or present in patched, but it is loosely adherent, easily comes off, and leaves significant marks on a cloth that is lightly wiped over the surface. SSPC SP10 (WAB)

Sampling, Detecting and Removing Soluble Salt Contamination Contaminants include chloride, ferrous ions, sulfates and nitrates Deposited onto surfaces while structure is in service Deposited during transportation of new steel overseas Soluble in water More difficult to remove from rough or pitted surfaces Pressure washing or water jetting using clean water

Sampling, Detecting and Removing Soluble Salt Contamination Proprietary salt removal-enhancing solutions available If salts are not detected and adequately removed they can become trapped beneath a newly installed coating system Consequences: osmotic blistering, underfilm corrosion, and premature coating failure Recycled abrasive may become contaminated

Salt Testing Methods Specifications may require testing of surfaces for soluble salt contamination Two steps: Extraction Analysis

Salt Testing Methods Methods of Extraction: Surface swabbing Latex patch/cell Latex sleeve Saturated contact pad Magnetic cell Filter paper saturation

Methods of analysis: Chloride ion test strips Drop titration Chloride ion detection tubes Conductivity meter Ferrous ion test strips (not shown) Nitrate ion test strips (not shown) Sulfate ion meter (not shown) Salt Testing Methods

Tolerable Levels of Soluble Salt Contamination No industry standard Dependent on the service environment & coating system ˗ Atmospheric exposure = higher tolerance ˗ Immersion service = lower tolerance The project specification must indicate the maximum quantity of soluble salts that can remain on the surface and be safely coated over

Abrasives Two broad categories Expendable – used once and then discarded Recyclable – breakdown rate slow, allows them to be used multiple times

Expendable Abrasives Mineral (occur naturally) Silica sand Garnet Staurolite Recycled glass Agricultural Abrasives

Recyclable Abrasives Steel grit (angular) Aluminum oxide (angular) Steel shot (rounded) Slag (not naturally generated). By-products of other industries processed into abrasives) Copper slag Nickel slag Coal slag

Recyclable Abrasives SSPC AB1 Specific Gravity Hardness Weight Change on Ignition Water Soluble Contaminates Moisture Content Oil Content Crystalline Silica Content Surface Profile Particle Size Distribution

Cleanliness Specifications for Metallic Abrasives SSPC AB 2 SSPC AB 3

Specifications for Metallic Abrasives SSPC AB 2 Cleanliness of recycled metallic abrasives “Indirect” requirement of SSPC abrasive blast cleaning standards (if abrasive is recycled) Testing for conformance Non-abrasive residue* Lead content (laboratory only) Water soluble contaminants* Oil content* * Can be verified in the field

Specifications for Metallic Abrasives SSPC AB 3 Standard addresses unused abrasive Abrasive cleanliness sections of AB 3 are an “indirect” requirement of SSPC abrasive blast cleaning standards Categorizes by Class Class 1: Steel Class 2: Iron Testing for conformance Abrasive size Specific Gravity Chemical composition Hardness Durability Cleanliness* Conductivity* * Can be verified in the field

Measurement of Ambient Conditions Prior to Final Surface Preparation No min or max air or surface temperature restrictions No relative humidity restriction If air temperature and relative humidity cause moisture from the air to condense on the surface, the surface may flash rust Verify that the temperature of the surface is at least 5°F higher than the dew point temperature

Surface Preparation/Primer Application Window Specification may dictate a maximum time period between final surface preparation and primer application 4 – 8 hours, same shift, may be addressed in the specificaion Inspector verifies primer application to prepared surfaces within allowable “window” If surface rusting is evident, the surfaces must be re-prepared to achieve the specified level of cleanliness (independent of elapsed time) Dehumidification equipment can extend the holding of the blast longer

Variables Weather ˗ Rain ˗ Fog ˗ Cold Temperatures

Variables Location ˗ Rivers ˗ Lakes ˗ Streams ˗ Oceans ˗ Mountains

Variables Proximity to the ground ˗ Substrate is close to the ground ˗ Cribbing

Variables Tank effluent in the tank Containment (could create internal micro climates due to poor design) Abrasive selection ˗ Reusable vs. expendable

Variables Containment and dehumidification equipment Inhibitors – Products that “hold blast” ˗ Require coating manufacturer approval in writing

Goal One size does not fit all and the need to: Investigate Proper Planning Material Equipment Schedule Location Weather Patterns End Result Project meets the contract documents

Chemical Plant Project Furnace Description 6 Story Box Approximately 14,000 sq. ft. of shell Multiple paint systems ˗ Ambient and high temperature paint systems Stack Approximately 90’ x 12’ diameter – 3,500 sq. ft. Decks Approximately 8 ft. wide with railing, stairs and ladders – 7,000 sq. ft. ˗ Ambient paint system

Chemical Plant Project Blower Approximately 2,500 sq. ft. ˗ Ambient paint system Miscellaneous pipe, equipment inside of containment Approximately 5,000 sq. ft. Multiple paint systems ˗ Ambient and high temperature paint systems Total – Approximately 35,000 sq. ft.