Corrosion and Protection of Steel Piles

Corrosion and protection of steel piles and sheet piles

William G. Ramos - NACE Certified Cathodic Protection Specialist and Senior Corrosion Technologist

Definition of Problem

Concrete Structures in marine environments are typically supported by steel-reinforced concrete piles that are subject to corrosion and concrete deterioration William G. Ramos - NACE Certified Cathodic Protection Specialist and Senior Corrosion Technologist

Cause of Deterioration

Corrosion of Reinforcing steels is one of the most important and prevailing mechanism of deterioration for Concrete Structures in Marine Environment William G. Ramos - NACE Certified Cathodic Protection Specialist and Senior Corrosion Technologist

What is Corrosion? Corrosion is the deterioration of a metal as a result of chemical reactions between it and the surrounding environment.

William G. Ramos - NACE Certified Cathodic Protection Specialist and Senior Corrosion Technologist

Corrosion is the process of a material returning to its thermodynamic state

William G. Ramos - NACE Certified Cathodic Protection Specialist and Senior Corrosion Technologist

WHAT CAUSES CORROSION OF STEEL-IN-CONCRETE?

William G. Ramos - NACE Certified Cathodic Protection Specialist and Senior Corrosion Technologist

Spalling Process

William G. Ramos - NACE Certified Cathodic Protection Specialist and Senior Corrosion Technologist

Corrosion Situation of Unprotected Structure in Marine Environment William G. Ramos - NACE Certified Cathodic Protection Specialist and Senior Corrosion Technologist

Corrosion Investigation

William G. Ramos - NACE Certified Cathodic Protection Specialist and Senior Corrosion Technologist

Objectives Our Primary Objectives for these works are:

• Assess the Corrosion conditions of concrete structures and piles of Jetty or Pier • Establish Recommendations for Possible Methods of Rehabilitation and Corrosion Control

William G. Ramos - NACE Certified Cathodic Protection Specialist and Senior Corrosion Technologist

How to evaluate the concrete condition?

William G. Ramos - NACE Certified Cathodic Protection Specialist and Senior Corrosion Technologist

The evaluation consist of the followings: • Visual Inspection • Observe, classify and document the appearance of distress and defects on exposed surfaces of the structure. Map distress and defects. • The visual inspection involve the measurement of cracks and spalling

William G. Ramos - NACE Certified Cathodic Protection Specialist and Senior Corrosion Technologist

The evaluation consist of the followings: Continuation…

• Delamination Survey: • Tap the concrete surface using a light hammer to identify delaminated concrete through a “hollow” impact sound at the locations with suspected corrosion activity.

ASTM D 4580 William G. Ramos - NACE Certified Cathodic Protection Specialist and Senior Corrosion Technologist

The evaluation consist of the followings: Continuation…

• Chloride Ion Content • The chloride ion content of the concrete can be taken from the concrete in question and subsequently send for the laboratory test.

William G. Ramos - NACE Certified Cathodic Protection Specialist and Senior Corrosion Technologist

The evaluation consist of the followings: Continuation…

• Depth of Carbonation • The depth of carbonation can be determined by spraying a phenolphthalein indicator onto a freshly fractured or cut concrete sample.

William G. Ramos - NACE Certified Cathodic Protection Specialist and Senior Corrosion Technologist

The evaluation consist of the followings: Continuation…

• Potential Measurements: • is one method used to estimate the corrosion activity of the reinforcing steel.

William G. Ramos - NACE Certified Cathodic Protection Specialist and Senior Corrosion Technologist

Potential Measurement Criterion for corrosion probability of steel in concrete Measured potential Ecorr (mV vs. CSE)

Corrosion probability

More positive than -200

Low, 90% probability of no corrosion

Between -200 and -350

Uncertainty

Less than -350

High, 90% probability of corrosion activity

ASTM C876-91

William G. Ramos - NACE Certified Cathodic Protection Specialist and Senior Corrosion Technologist

Corrosion Control Corrosion control comes in many forms

One, or a combination of the following measures can achieve corrosion protection: - Paint, Zinc Coating - Cement, Grout or Concrete Cover - Pile Encasement / Jacketing - Cathodic Protection System

William G. Ramos - NACE Certified Cathodic Protection Specialist and Senior Corrosion Technologist

Cathodic Protection Introduction The first practical use of cathodic protection is generally credited to English Chemist, Sir Humphrey Davy in the 1820’s.

Sir Davy found that he could preserve copper in sea water by the attachment of small quantities of iron or zinc; the copper became, as Davy put it, “CATHODICALLY PROTECTED”.

William G. Ramos - NACE Certified Cathodic Protection Specialist and Senior Corrosion Technologist

How does Cathodic Protection stop corrosion? Cathodic protection prevents corrosion by converting all of the anodic (active – likely to corrode) areas on the metal surface to cathodic (passive) areas by supplying electrical current (or free electrons) from an alternate source.

William G. Ramos - NACE Certified Cathodic Protection Specialist and Senior Corrosion Technologist

There are two methods of Cathodic Protection System

William G. Ramos - NACE Certified Cathodic Protection Specialist and Senior Corrosion Technologist

Impressed Current Cathodic Protection System

i

A source of DC electric current is used to help drive the protective current (electrochemical reaction) to make the structure surface cathode. William G. Ramos - NACE Certified Cathodic Protection Specialist and Senior Corrosion Technologist

Sacrificial Cathodic Protection System

Attaching a more active metal to form a new anode (making the existing anode the cathode) - resulting in the new material (sacrificial anode) being corroded rather than the protected material William G. Ramos - NACE Certified Cathodic Protection Specialist and Senior Corrosion Technologist

William G. Ramos - NACE Certified Cathodic Protection Specialist and Senior Corrosion Technologist

Management Strategies Do Nothing Conventional Repair Repair methods will not stop the corrosion; they are short term fixes and do not solve the problem.

Application of Corrosion Prevention and Control According to the US Federal Highway Administration, CATHODIC PROTECTION is the “only rehabilitation technique that has been proven to stop “corrosion”.

William G. Ramos - NACE Certified Cathodic Protection Specialist and Senior Corrosion Technologist

Thank You !

No one wants to make front page headlines for all the wrong reasons William G. Ramos - NACE Certified Cathodic Protection Specialist and Senior Corrosion Technologist