Common AST Inspection Findings: Issues and Fixes

Aboveground storage tanks are built for durability, but in the field, most inspection findings come down to a handful of repeat issues: corrosion that starts small, coatings that fail early, drainage that gets neglected, and documentation that is incomplete when you need it most. The good news is that many of these findings are preventable, and when they are caught early, they are usually far less expensive to correct.

This guide breaks down the top AST inspection findings inspectors see most often, why they happen, how they are identified, and practical ways to fix them and keep them from coming back.

Why common findings matter for AST owners and operators

The real cost of repeat deficiencies

A repeat finding is rarely just an inconvenience. It can lead to unplanned downtime, lost product, accelerated corrosion, and avoidable repair work. It can also complicate environmental risk management, insurance conversations, and compliance planning. Over time, the cost of “small” findings adds up because access, prep work, and reinspection often cost as much as the repair itself.

Findings are usually symptoms, not surprises

Most deficiencies do not appear overnight. They are typically the visible outcome of drainage issues, coating breakdown, poor housekeeping, or missed maintenance intervals. If you treat the symptom only, you risk seeing the same finding again at the next inspection.

Where findings come from

Many issues are identified during routine inspections, after a change in service, following repairs, or during pre audit readiness checks. Each of these situations tends to highlight different problems, which is why having a consistent prevention plan matters.

Quick primer: what inspectors typically evaluate on aboveground storage tanks

The main inspection areas

Most AST inspections focus on these buckets:

• Tank shell and roof condition
• Bottom and annular area indicators
• Foundations and supports
• Piping, valves, and supports
• Overfill protection and venting
• Secondary containment
• Safety systems, labeling, and site conditions
• Documentation and inspection history

Visual inspection vs NDT vs thickness readings

Visual inspection is often the starting point. When an inspector sees corrosion patterns, distortion, coating failure, or suspect weld areas, that can trigger follow up non destructive testing. Common follow ups include ultrasonic thickness testing, targeted NDT for indications at welds, and floor scanning methods when bottom condition needs better clarity.

Why construction codes and service conditions matter

Tank age, product type, water bottoms, temperature cycling, and local environment all influence risk. A tank in a coastal or chemically aggressive environment may see coating failure and external corrosion earlier than a similar tank in a dry inland setting. Likewise, poor drainage can accelerate deterioration even on a newer tank.

The top AST inspection findings and how to fix them

Below are the most common findings, organized to help you quickly connect what inspectors see with what you can do next.

1) External corrosion on the shell, roof, and nozzles

What inspectors commonly find

• Corrosion at the lower shell course and chime area
• Rust at roof penetrations, nozzles, and around appurtenances
• Deterioration on ladders, platforms, handrails, and attachment points

Why it happens
Moisture sits where coatings are thin or damaged, especially at edges, weld toes, bolted connections, and areas that trap debris. Once corrosion begins, it can spread under coatings and become harder to stop with simple touch ups.

How it is spotted
Visual assessment identifies rusting, flaking, and coating holidays. Thickness readings may be recommended where loss is suspected or where corrosion patterns are widespread.

Fix options

• Clean and prep the affected area properly before recoating
• Repair or replace compromised components where section loss is significant
• Use corrosion mapping or targeted thickness readings to confirm remaining thickness where needed

Prevention checklist

• Schedule coating inspections and touch ups, not just full repaints
• Keep the tank exterior clean, especially around the base and roof penetrations
• Address minor coating damage quickly before corrosion spreads

2) Coating breakdown and poor surface preparation

What inspectors commonly find

• Blistering, peeling, and underfilm corrosion
• Pinholes and early coating failure at welds and edges
• Inconsistent film build and poor adhesion

Why it happens
Coatings often fail early when surface preparation is insufficient or when a coating system is not well matched to the service environment. Edges and weld areas are frequent weak points because they are harder to coat evenly.

How it is spotted
Inspectors look for visual coating defects, adhesion issues, and corrosion patterns that suggest failure beneath the coating. When needed, additional coating QA checks can be recommended.

Fix options

• Rework coating in failed zones using proper prep standards
• Select a compatible coating system based on service conditions
• Document coating QA and QC so future inspections have a clear baseline

Prevention checklist

• Use a spec driven coatings plan, not a one size approach
• Verify dry film thickness during application
• Pay extra attention to edges, welds, and roof details during coating work

3) Tank settlement, out of level conditions, and foundation problems

What inspectors commonly find

• Uneven base conditions and out of level measurements
• Shell distortion, cracking, or visible stress indicators
• Stair or piping misalignment that suggests movement

Why it happens
Settlement can be driven by poor subgrade support, erosion, inadequate drainage, or long term loading effects. Even small movements can strain piping, distort shell plates, and create points where water collects.

How it is spotted
Inspectors may observe uneven gaps, tilt, distortion patterns, and unusual stress points. When settlement is suspected, a more detailed evaluation may be recommended.

Fix options

• Engineering assessment to determine severity and root cause
• Foundation repair, stabilization, or releveling where appropriate
• Adjust piping supports and flexibility to reduce strain

Prevention checklist

• Maintain site grading and drainage around the tank
• Monitor for early warning signs such as new pooling or misalignment
• Include periodic level checks in your maintenance routine

4) Water intrusion, poor drainage, and evidence of water bottoms

What inspectors commonly find

• Standing water on roofs or in containment areas
• Roof drain issues and compromised seals
• Corrosion patterns consistent with persistent moisture exposure

Why it happens
Drainage systems clog, seals degrade, and housekeeping slips. Water that sits on a roof or around the base creates a corrosion accelerator. Over time, the tank may develop more serious integrity concerns.

How it is spotted
Visual inspection identifies standing water, clogged drains, deteriorated seals, and corrosion patterns. Follow up inspection planning may be recommended when moisture exposure suggests hidden risk.

Fix options

• Repair roof drains, seals, and drainage pathways
• Improve housekeeping and remove debris that blocks flow
• Plan follow up inspection steps if indicators suggest broader impact

Prevention checklist

• Routine roof and containment drainage checks after heavy weather
• Keep drains clear and document maintenance
• Treat recurring standing water as a priority issue, not a nuisance

5) Secondary containment deficiencies

What inspectors commonly find

• Cracks, penetrations not sealed, and liner damage
• Vegetation growth and sediment buildup that reduces capacity
• Drain management issues and signs of uncontrolled discharge pathways

Why it happens
Containments are often treated as passive structures until something goes wrong. Weather, age, and site activity can degrade liners and concrete. Growth and debris can reduce effective capacity.

How it is spotted
Inspectors look for cracks, gaps at penetrations, evidence of erosion, and reduced freeboard.

Fix options

• Repair liners or concrete and seal penetrations properly
• Restore capacity by removing debris and vegetation
• Implement controlled drainage procedures appropriate for your site requirements

Prevention checklist

• Walk down containment routinely, not just before inspections
• Keep drainage procedures documented and consistent
• Treat vegetation and sediment as capacity and compliance risks

6) Piping, valves, and supports in poor condition

What inspectors commonly find

• Corrosion on piping and supports, including hidden risk areas
• Unsupported lines, sagging runs, and worn valve components
• Leaking flanges and degraded gaskets

Why it happens
Piping systems see vibration, thermal movement, and weather exposure. Supports shift, corrosion develops at contact points, and small leaks become chronic issues when not corrected promptly.

How it is spotted
Visual inspection identifies corrosion, alignment issues, and leakage. Targeted NDT may be recommended when localized thinning is suspected.

Fix options

• Replace or repair degraded valves, flanges, and damaged piping sections
• Add or correct supports, guides, and anchors as needed
• Conduct leak testing and verify repairs

Prevention checklist

• Implement a piping condition program that includes regular walkdowns
• Address support issues early to prevent strain and cracking
• Track recurring leak points and correct root causes

7) Overfill protection, vents, and safety systems not functioning as intended

What inspectors commonly find

• Vents and flame arrestors damaged or obstructed
• Overfill alarms not tested or documentation missing
• Missing signage or unclear operating procedures

Why it happens
Safety systems often fail due to lack of routine functional testing, exposure damage, or undocumented changes over time.

How it is spotted
Inspectors verify presence, condition, and evidence of testing. When testing records are missing, the system may be treated as unverified.

Fix options

• Functional testing, calibration, and replacement where needed
• Verify setpoints and operational procedures
• Restore and standardize signage and labeling

Prevention checklist

• Put proof testing on a defined schedule and document results
• Train operators on normal and abnormal operating conditions
• Review systems after maintenance or operational changes

8) Labeling, records, and inspection documentation gaps

What inspectors commonly find

• Missing nameplate information or unclear asset identification
• Incomplete inspection history and repair records
• Prior findings without closeout evidence

Why it happens
Records get spread across emails, binders, and different teams. Over time, institutional knowledge leaves, and the paper trail becomes incomplete.

How it is spotted
Inspectors request documentation and compare it to tank identification, prior reports, and repair evidence. Gaps can slow the inspection process and complicate decision making.

Fix options

• Rebuild an inspection file with a clear asset history
• Standardize repair closeout documentation
• Align records so future inspections start with a reliable baseline

Prevention checklist

• Maintain a single source of truth for tank records
• Log findings, repairs, and verification steps consistently
• Treat documentation as part of integrity, not just administration

Prevention playbook: How to Reduce Findings Before the Next Inspection

Build a findings to action workflow

• Classify each finding by urgency and operational impact
• Assign an owner, a due date, and a verification step
• Close the loop with documentation and photos so the next inspection has proof of correction

Create an annual inspection readiness checklist

Include recurring checks for:

• Housekeeping and debris removal
• Roof and containment drainage
• Coating touch ups and corrosion watch areas
• Valves, vents, and overfill system checks
• Containment walkdowns for cracks, penetrations, and capacity
• Documentation review and report closeouts

Use the right method at the right time

When visual inspection raises questions, follow up with targeted NDT or thickness readings. The goal is to verify conditions efficiently and avoid guessing. A method matched to the suspected issue helps you plan repairs with more confidence.

Budget smarter with condition based maintenance

Combine access work where possible. Coordinating coating touch ups, piping repairs, and verification work during the same access window often reduces total cost and limits disruption.

What to expect during an AST inspection and how NDT Tanknicians helps

Typical inspection workflow

• Pre job planning and site coordination
• Safety and access planning
• Field inspection and any required NDT
• Findings report with photos and prioritized recommendations
• Repair guidance and follow up verification planning when needed

Deliverables that make it easy to act

A useful inspection report does more than list issues. It supports decisions. Expect clear photos, location specific notes, prioritization that separates urgent items from planned maintenance, and practical next steps.

Common next steps after findings

Depending on what is found, next steps may include coordinating repairs, aligning coating contractors to a scope, performing follow up NDT in localized areas, and closing out documentation so the tank history is complete.

Ready to reduce repeat findings and improve tank reliability?

Contact NDT Tanknicians to schedule an AST inspection or a pre inspection readiness review. If you already have prior reports, we can help you triage findings, prioritize fixes, and recommend the most appropriate verification approach.

Frequently Asked Questions

How often should aboveground storage tanks be inspected?

Inspection frequency depends on tank design, service conditions, and applicable requirements at your facility. Many organizations use a planned schedule that combines routine walkdowns with periodic formal inspections and condition verification.

Which findings are considered urgent versus routine maintenance items?

Urgent findings typically include active leaks, severe corrosion or section loss, compromised containment, or safety systems that cannot be verified as functional. Routine items may include early coating wear or housekeeping issues, but they can become urgent if ignored.

Can NDT methods detect bottom corrosion without taking a tank out of service?

In many cases, specific NDT approaches can provide insight into bottom condition without a full internal inspection, depending on tank configuration and site constraints. An inspector can recommend the most practical approach after an initial assessment.

What documentation should we have ready before an AST inspection?

Have prior inspection reports, repair records, coating history, overfill and safety system testing records, and any relevant drawings or asset identification details. A clean, consistent record set often makes inspections faster and recommendations clearer.

How do secondary containment issues affect compliance and risk?

Containment deficiencies can increase environmental exposure risk during releases and can create compliance concerns if capacity, integrity, or drainage controls are not maintained. Routine walkdowns and prompt repairs help reduce that risk.