Winning the War Against Corrosion: Practical Principles Every Engineer Should Understand

Last Updated 2 months ago by Kenya Engineer

Corrosion is one of those quiet enemies of engineering—rarely dramatic, often invisible at first, but relentlessly expensive. It eats away at bridges, tanks, pipelines, factories, ships, street furniture and even our homes. By the time corrosion becomes obvious, the damage is usually well advanced and costly to reverse.

For engineers working in Kenya and across the region—where humidity, marine exposure, industrial pollution and inconsistent maintenance regimes are common—understanding corrosion control is not optional. It is a professional responsibility tied directly to public safety, asset reliability and national development.

At its core, corrosion control is not just about paint. It is about understanding how metals behave, how environments attack them, and how proper preparation, coating selection, application and inspection work together as one system to protect valuable assets over their intended service life.

Understanding Corrosion: More Than Just Rust

Corrosion of steel is fundamentally an electrochemical process. When iron or steel is exposed to moisture, oxygen and dissolved salts or pollutants, tiny electrical cells form naturally on the metal surface. Some areas act as anodes, others as cathodes. Once this microscopic “battery” is created, metal begins to dissolve at the anode, forming rust.

This explains why corrosion can occur even on a single piece of steel without any external electrical source. Variations in stress, crystalline structure, weld zones or surface contamination are enough to initiate corrosion.

Environmental factors significantly influence corrosion rates. High relative humidity, common in many Kenyan regions, allows moisture films to persist on steel surfaces. Coastal salt spray introduces chlorides that aggressively attack protective films, while industrial emissions contribute sulphates and other corrosive compounds. Together, these conditions create an ideal environment for accelerated deterioration.

Surface Preparation: Where Protection Truly Begins

No protective coating system can outperform its surface preparation. This principle is repeatedly confirmed in corrosion failure investigations worldwide.

Steel typically leaves the mill covered with mill scale—a tightly adherent oxide layer that offers little real protection once moisture penetrates beneath it. Painting over mill scale may look acceptable initially, but it often results in premature coating failure.

Abrasive blast cleaning remains the most effective method of surface preparation, particularly for aggressive environments such as marine, industrial or immersion service. Higher standards of blasting, such as near-white or white metal finishes, provide a clean, profiled surface that allows coatings to bond effectively.

Lower-cost alternatives such as power-tool or hand-tool cleaning may be acceptable in mild environments, but they struggle to remove corrosion from pits, corners and crevices. In harsh exposure conditions, these shortcuts usually translate into reduced coating life and higher long-term maintenance costs.

Weld areas deserve special attention. Weld spatter, flux residues and heat-affected oxides are common initiation points for corrosion. Removing spatter, smoothing sharp edges and neutralising alkaline residues can significantly extend coating life with minimal additional effort.

Adhesion And Surface Profile: The Hidden Foundation

Coatings adhere to steel through a combination of mechanical and chemical bonding. Mechanical adhesion depends heavily on surface profile—the microscopic peaks and valleys created during abrasive blasting.

A properly profiled surface increases effective surface area and allows the coating to anchor firmly. However, excessive roughness can be counterproductive if coating thickness is insufficient to fully cover the peaks. As a general guideline, surface profile should not exceed one-third of the total dry film thickness of the coating system.

Balancing profile depth with coating build is critical and should be clearly defined at specification stage rather than left to chance on site.

Coating Application: Skill Still Matters

Applying protective coatings is often mistaken for simple painting. In reality, it is a skilled discipline requiring an understanding of materials, equipment and environmental conditions.

Weather plays a decisive role. High humidity can cause condensation on steel surfaces, preventing proper adhesion. Extremely hot conditions may cause solvents to evaporate too rapidly, leading to pinholes, dry spray or cracking. Cold temperatures slow curing reactions and make it difficult to achieve specified film thickness.

Different application methods serve different purposes. Brush application ensures good wetting of irregular surfaces and is particularly effective for primers and detail work. Rollers provide speed on flat areas but are less effective on complex steelwork. Spray methods—conventional, airless or electrostatic—offer speed and film thickness control but demand trained operators and strict quality control.

Regardless of method, sharp edges, welds and fasteners must always receive extra attention, as coatings naturally thin out on these features during drying.

Choosing The Right Coating System

There is no universal “best paint.” Effective corrosion protection relies on selecting the right system for the environment and service conditions.

Primers provide adhesion and corrosion inhibition. Zinc-rich primers offer sacrificial protection, while epoxy primers provide excellent barrier properties. Intermediate coats build film thickness and enhance resistance to moisture and chemicals. Finish coats protect the system from ultraviolet exposure, weathering and mechanical damage while also contributing to appearance.

The compatibility of all layers is essential. Using incorrect thinners or incompatible products can undermine an otherwise well-designed system. Coating selection should always be guided by exposure conditions, expected service life and manufacturer recommendations.

Inspection: Verifying What The Eye Cannot See

Inspection is a critical but often undervalued component of corrosion control. Its purpose is not to slow down work but to ensure that specifications are achieved consistently.

Inspectors must verify surface cleanliness, profile depth, environmental conditions during application and dry film thickness. Instruments must be properly calibrated, and acceptable tolerances agreed upon in advance.

Many coating failures originate not from product defects, but from deviations during surface preparation or application that were never detected or corrected.

Health And Safety: Non-Negotiable In Corrosion Control

Abrasive blasting and coating application present serious occupational hazards. Dust inhalation, solvent exposure, high-pressure equipment and working at heights demand strict adherence to safety procedures.

Proper personal protective equipment, adequate ventilation, fire precautions and clear site controls are essential. Airless spray equipment, in particular, poses severe injection injury risks if mishandled.

A strong safety culture protects not only workers but also project timelines, budgets and reputations.

Corrosion Control Is A System, Not An Afterthought

Corrosion control is one of the most cost-effective investments an engineer can make. Done properly, it extends asset life, reduces maintenance costs and improves safety. Done poorly, it results in endless repainting cycles and premature failures.

Steel rarely fails suddenly. It deteriorates gradually, giving engineers every opportunity to intervene early. Understanding corrosion, respecting preparation, choosing the right systems and insisting on proper application and inspection is how we win the war against corrosion.

About the Author

Nick Karakasch is the retired Principal Consultant to Total Corrosion Consultants, Melbourne Australia. Nick’s experience spans 55 years specializing in services to the Protective Coating, Galvanizing, and Fire Protection Industries. He spent many years in a management and technical capacity with the Dimet Coating organisation, the company which invented Inorganic Zinc Silicate Coatings by their founding Director, Victor Nightingall. He has also been the Executive Marketing Manager to the Galvanizers Association of Australia. Whilst living in South Africa in 1970’s he was employed as a Site Contracts Manager by R.J. Southey Pty Ltd. Africa’s largest Corrosion Prevention Contractors.